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Author Topic: Mark Dubovoy's Leica S2 Review  (Read 17660 times)
Guy Mancuso
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« Reply #80 on: June 30, 2010, 06:22:46 PM »
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Quote from: eronald
Cmon guy, that don't explain the rarity of brick wall raws

Edmund


ROTFLMAO. Yea this is just a sun baked state . Brick walls last about a day here than burst into flames. LOL

Everyone please turn you AC units towards Arizona. Today it is cool at 106
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Steve Hendrix
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« Reply #81 on: June 30, 2010, 06:22:47 PM »
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Quote from: Rob C
Fred

I well remember watching the Dukes series; it was a fascinating look into the imaginary life of the American boondocker. It also represented something almost aspirational - don't laugh - what with its CB radio etc. which, believe it or not, was banned in the UK for quite some time, as were the pirate radio stations, of which Radio Caroline (North and South) was my favourite. Many an otherwise lonely night in the darkroom was helped along by the Mamas and the Papas chanting about their 'darkest hour' being 'just before dawn'! Too bloody true! Another one that I loved, Radio Scotland, was local, and it was on when they announced that Elvis had left the building. Also, there was an ad for a modelling agency on it for a while, that I followed up and which led to my first contact with a pro version (as raw as myself at the time) of the genre from whence it all (my real photo life) began. So thanks, pirates.

But the Dooks' car: also a huge part of the US dream for other people. Living in India for some years I was quite used to the sight of US wheels of the 40s - early 50s; back in the UK (a song there?) maybe all folks saw of them was around USAF bases and compared with the junk that we produced in Britain and the prices of said rubbish when compared to the US home-buys, no wonder we thought the US a promised land. Somehow, that Ford Consul was never going to look cool with a Union Jack on the roof. The Mini graced some such motifs during the Carnaby Street era in the home-grown version of self-expression but it was something quaint rather than macho, art born of poverty.

I guess that America still remains a bit of a dream for non-Americans; we have been raised on the Hollywood version of reality and it was years before I, for one, accepted that not all Americans had V8s, swimming pools and lived in houses with white fences with a barn and a horse at the back. All cowboys played the guitar, had balls of steel that could withstand leaping down into a saddle from extraordinary hights (strong nags, too!) and, best of all, nobody ever had to work. Well, perhaps not best of all; best of all was that all the girls were fantastically beautiful, passed the days in school, cafés or flower shops, appeared to have no guile whatsoever and anyone could just walk up and stand a pretty good chance of scoring! The one bad thing: we all had to learn how to walk like Robert Mitchum. It was half-way easier for me, being called Robert, but that half was the only bit that worked.

I suspect that some large percentage of the US still quietly believes parts of the same dream: you'd have too - why else continue the battle against the odds? For the rest of us - maybe disillusion sets in earlier, not a happier choice. Obviously enough.

But without dreams we might as well emulate the lemming.

Rob C


Yes it's true. US girls are easy.



Steve Hendrix
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Steve Hendrix
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wildlightphoto
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« Reply #82 on: June 30, 2010, 09:46:49 PM »
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Quote from: Guy Mancuso
... I am not going to put great images up for raws to be used anywhere and YOU should know better than that. They are test files pure and simple but putting up real work is NOT something I will do especially the raws and no one testing these rigs will either and you know the reasons.
I agree and furthermore I'll never test any equipment on important shoots because optimal or not I have to have the camera ingrained in my soul when the photons meet the silicon otherwise I'm going to screw something up.  For testing equipment I'll use repeatable boring subjects where a screwup isn't a big deal.
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dubomac
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« Reply #83 on: June 30, 2010, 10:09:41 PM »
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Let me focus (pun intended) on a single sentence in David's post:

"The stepper motors in the H lenses do not suffer from this issue".

Therefore, according to David, Hasselblad uses stepper motors to focus their lenses.

The definition of a stepper motor is as follows: A stepper motor is a special type of electric motor that moves in increments, or steps, rather than turning smoothly as a conventional motor does.

Therefore, the Hasselblad lenses focus in steps.

I rest my case.





Quote from: David Grover / Hasselblad
Ok, I have found myself with a bit of airport time so will respond to Mark and Michael in one post.


From Mark...

My understanding from the technical papers and my direct conversations with at least one MF manufacturer is that the issue is not measuring distances with a phase detection system. You are correct that this can be done continuously. The issue is the mechanics of the lens itself. You need quite a bit of torque to get the focusing system to start moving. The system has inertia, as well as gears and other moving parts. There is a limit as to how "continuous" these parts can move. There is also a limit as to how fast you can apply the brakes and stop the movement. When you put all that together, the mechanisms themselves are not continuous and cannot be moved in infinitesimally small increments. They are "jumpy" and they focus in discrete steps or zones.


I expect the manufacturer you are talking about does not use motors inside the lens to drive the focussing optics but rather a motor inside the camera body?  Hasselblad uses motors inside the lens, so a larger lens can use a larger motor etc etc.

The advantage of the motor inside the lens is that there is no mechanical connection needed to be made when attaching the lens to the camera body.  The small armature that protrudes from the lens mount to drive the mechanics I would expect to have some degree of mechanical slop, albeit a small amount.

Therefore as you get to the far range of focus and smaller amounts of movement on the optics need to be applied then the mechanical intolerance (if thats a word) would render it difficult to make precise steps and therefore have a jumpy effect with the result be a loss in finite focussing.  So I assume this is the conclusion from your conversations with Mamiya?  Please correct me if I am wrong.

The stepper motors in the H lenses do not suffer from this issue.  If you connect an H camera to our Phocus software you can see this yourself.  Using the camera control tool, you can manipulate the focus using the + and - buttons.  Hold down the Cmd key whilst clicking these buttons and this will give you an extremely fine focus.  ie they can be moved in infinitesimally small increments.

I hope that clears it up from my end.

If you wanted to research further, what you could investigate is when the AF drive goes back at forth at some point the camera will decide “Im in focus within my factory set tolerance”.  I cannot find any data from Canon and Nikon which describes this tolerance.  Perhaps it is mentioned in the Leica articles?

The tolerance for us does not change at either end of the focussing scale.

From Michael...

What I've learned so far is that while phase detection AF systems do not have "zones" the way that contrast detection systems do, they do indeed focus their lenses in discrete steps, and this is an understood issue in medium format AF design due to such systems' more shallow DOF than 35mm or smaller systems.

I hope with my words above I have tried to describe that this is not the case with the Hasselblad AF system.

From my work eons ago as a motorsport photographer (Using Manual Focus!!  Ugh!!) I would expect a Nikon / Canon 400mm/500mm+ does not have very much DOF at the infinity scale.  Perhaps it is interesting to know from our readers if they feel the 35mm systems fail at infinity focussing?

To close, I am sorry to hear if you felt that it was hard to get in touch with someone at Hasselblad.  However, I have been a pretty active poster here for a couple of years and am only a PM away.

Best Regards,




David
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dubomac
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« Reply #84 on: June 30, 2010, 10:52:21 PM »
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Folks:

The time has come to put final closure to all the arguments and speculation about autofocus systems.

I have spent the last few days in contact with all the relevant top level technical personnel at PhaseOne and Leica.  To make sure you all understand this, I have been in contact with the people that actually designed the current autofocus systems, with the people that manufacture them, with the Technical Directors in charge of the product lines and with the Chief Technical Officers.  This is what I call "the horse's mouth".

In my conversations with these companies, they have verified that the statements in my article are factually and technically correct:

- Autofocus systems work in small steps and not continuously.  

- They have verified that my prior posts on this forum are technically correct.

- Finally, they have also verified that distant objects are the most likely to cause autofocus failures.  As mentioned in my article, this is exactly what I have observed in the field, and the explanation given in my prior post about this is technically correct.

The Technical Director in charge of the S2 at Leica put it most eloquently.  I am always sensitive about not disclosing information that might be considered confidential by a company, so I apologize to the curious members of the forum who would like to know the exact numbers.  I will leave it up to Leica as to whether they wish to publicly disclose those numbers.

Here is the quote:

"Reliability is not only one of the major features of the complete S-system but is also a very important point with respect to AF operation. That the S2 AF performance (reliability, speed and precision) is so high has many reasons. It is an advantage to have very small focus steps at distances approaching infinity (where you have the least depth of field), and where the lens has to focus very precisely. The Leica Summarit-S 70mm has a focus resolution of ___ micron (=1 focus step). Furthermore there is a f-stop correction depending on the focus distance. The operating temperature, which also has a big impact on AF precision, is considered as well. But most important is that all lenses and cameras are checked very carefully (and if necessary corrected) by our QA department before they are delivered to our customers. The AF and image sensor planes (CCD) are aligned most precisely. These smallest tolerances are only possible with an integrated digital system! "

         
To summarize:

While I knew at the time that I wrote the article that all the information in it was thoroughly researched, and factually and technically correct, having done the exercise a second time with the folks mentioned above, I once again stand 100% behind everything written in my article about the S2

Best regards and good luck to all.

Mark Dubovoy






Quote from: David Grover / Hasselblad
Ok, I have found myself with a bit of airport time so will respond to Mark and Michael in one post.


From Mark...

My understanding from the technical papers and my direct conversations with at least one MF manufacturer is that the issue is not measuring distances with a phase detection system. You are correct that this can be done continuously. The issue is the mechanics of the lens itself. You need quite a bit of torque to get the focusing system to start moving. The system has inertia, as well as gears and other moving parts. There is a limit as to how "continuous" these parts can move. There is also a limit as to how fast you can apply the brakes and stop the movement. When you put all that together, the mechanisms themselves are not continuous and cannot be moved in infinitesimally small increments. They are "jumpy" and they focus in discrete steps or zones.


I expect the manufacturer you are talking about does not use motors inside the lens to drive the focussing optics but rather a motor inside the camera body?  Hasselblad uses motors inside the lens, so a larger lens can use a larger motor etc etc.

The advantage of the motor inside the lens is that there is no mechanical connection needed to be made when attaching the lens to the camera body.  The small armature that protrudes from the lens mount to drive the mechanics I would expect to have some degree of mechanical slop, albeit a small amount.

Therefore as you get to the far range of focus and smaller amounts of movement on the optics need to be applied then the mechanical intolerance (if thats a word) would render it difficult to make precise steps and therefore have a jumpy effect with the result be a loss in finite focussing.  So I assume this is the conclusion from your conversations with Mamiya?  Please correct me if I am wrong.

The stepper motors in the H lenses do not suffer from this issue.  If you connect an H camera to our Phocus software you can see this yourself.  Using the camera control tool, you can manipulate the focus using the + and - buttons.  Hold down the Cmd key whilst clicking these buttons and this will give you an extremely fine focus.  ie they can be moved in infinitesimally small increments.

I hope that clears it up from my end.

If you wanted to research further, what you could investigate is when the AF drive goes back at forth at some point the camera will decide “Im in focus within my factory set tolerance”.  I cannot find any data from Canon and Nikon which describes this tolerance.  Perhaps it is mentioned in the Leica articles?

The tolerance for us does not change at either end of the focussing scale.

From Michael...

What I've learned so far is that while phase detection AF systems do not have "zones" the way that contrast detection systems do, they do indeed focus their lenses in discrete steps, and this is an understood issue in medium format AF design due to such systems' more shallow DOF than 35mm or smaller systems.

I hope with my words above I have tried to describe that this is not the case with the Hasselblad AF system.

From my work eons ago as a motorsport photographer (Using Manual Focus!!  Ugh!!) I would expect a Nikon / Canon 400mm/500mm+ does not have very much DOF at the infinity scale.  Perhaps it is interesting to know from our readers if they feel the 35mm systems fail at infinity focussing?

To close, I am sorry to hear if you felt that it was hard to get in touch with someone at Hasselblad.  However, I have been a pretty active poster here for a couple of years and am only a PM away.

Best Regards,




David
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Rob C
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« Reply #85 on: July 01, 2010, 02:14:05 AM »
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Quote from: dubomac
Here is the quote:

"Reliability is not only one of the major features of the complete S-system but is also a very important point with respect to AF operation. That the S2 AF performance (reliability, speed and precision) is so high has many reasons. It is an advantage to have very small focus steps at distances approaching infinity (where you have the least depth of field), and where the lens has to focus very precisely. Mark Dubovoy


Isn't there something a little skewed about this statement?

Rob C



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PaulSchneider
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« Reply #86 on: July 01, 2010, 02:28:41 AM »
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So who is right now and who's not?
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fredjeang
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« Reply #87 on: July 01, 2010, 02:50:39 AM »
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Quote from: dubomac
Folks:

The time has come to put final closure to all the arguments and speculation about autofocus systems.

I have spent the last few days in contact with all the relevant top level technical personnel at PhaseOne and Leica.  To make sure you all understand this, I have been in contact with the people that actually designed the current autofocus systems, with the people that manufacture them, with the Technical Directors in charge of the product lines and with the Chief Technical Officers.  This is what I call "the horse's mouth".

In my conversations with these companies, they have verified that the statements in my article are factually and technically correct:

- Autofocus systems work in small steps and not continuously.  

- They have verified that my prior posts on this forum are technically correct.

- Finally, they have also verified that distant objects are the most likely to cause autofocus failures.  As mentioned in my article, this is exactly what I have observed in the field, and the explanation given in my prior post about this is technically correct.

The Technical Director in charge of the S2 at Leica put it most eloquently.  I am always sensitive about not disclosing information that might be considered confidential by a company, so I apologize to the curious members of the forum who would like to know the exact numbers.  I will leave it up to Leica as to whether they wish to publicly disclose those numbers.

Here is the quote:

"Reliability is not only one of the major features of the complete S-system but is also a very important point with respect to AF operation. That the S2 AF performance (reliability, speed and precision) is so high has many reasons. It is an advantage to have very small focus steps at distances approaching infinity (where you have the least depth of field), and where the lens has to focus very precisely. The Leica Summarit-S 70mm has a focus resolution of ___ micron (=1 focus step). Furthermore there is a f-stop correction depending on the focus distance. The operating temperature, which also has a big impact on AF precision, is considered as well. But most important is that all lenses and cameras are checked very carefully (and if necessary corrected) by our QA department before they are delivered to our customers. The AF and image sensor planes (CCD) are aligned most precisely. These smallest tolerances are only possible with an integrated digital system! "

         
To summarize:

While I knew at the time that I wrote the article that all the information in it was thoroughly researched, and factually and technically correct, having done the exercise a second time with the folks mentioned above, I once again stand 100% behind everything written in my article about the S2

Best regards and good luck to all.

Mark Dubovoy

1) Refreshing! it results that when the information is asked at the right sources we may once for a while give up the forum erasmus scientist speculations, but I'm afraid it won't happen anyway and "good" (and scientific of course) arguments against will fall very soon on the battle field. Ok, at least another perspective has emerged.

And I would like to have some confirmations from the same sources about that DR stuff that always puts the forum into flammes, when everybody see 1 stop or when I see 4 in practise. As I'm human, I'd like to know where I'm failing or if this just 1 stop is just a collective illusion...

Anyway, maybe before asking for the Mark's head like in the French revolution we should think if we are really capable of managing the right information.(and I'm including myself here)

There is a lot of lecture over the internet.

2) About the print/web. This is simply ridiculous IMO.
If you can't judge images on the web I doubt you'll be able to on a print, regardless on the differences in bits and resolution.

3) ............About the last BCooter post............
This one was psychadelic.

If there is one person on this forum who can have access to the gear and test in real field and produce top images with it is BCooter.I can't beleive that one of the world's most influent commercial photographer does not have the right key to open these doors.

Or he does not have the time because of his agenda to do the testings to his standards, or he likes teasing.

I always find the BC posts very informatives and frankly "above the crowd", except when he comes over and over again on how bad are those testings.
I join the Guy's Mancuso post here on that matter.

Don't get me wrong, BC is right in essence. I'm also fed up to see the happy familly kind of pictures that are generally spread over the internet in gear testing.
And it is true that very little if no information is deliver regarding the PP, the tech issues, the tether task etc...
But the problem is exactly what you see here: Even if people would do those testing in BC's minimum standards, they are poorly rewarded.

Immediatly the "expert's forums" will jump agressivly on the scenery with any arguments against the lightning, that this or that mistake was done with the software,
that the writter has done a big semantic error, that they did not tether with the right cable, that the computer was not maintained properlly, that he should have use this other lens that focus faster,
etc...and in the best cases with manners but generally agressive and cynical reactions.
that anyway we can't judge the pics over internet etc...

So you have all the moderators suddenly busy, and I imagine they will like to use their time better, in order to keep the forum elegance and manners. No surprise if people who could do the testing
in the most professional way say no thanks.

If Raw files where deliver it would just be the same story.
So, even if someone was tempted to do those testings in a real pro environment it would generally not happen because of those reasons.
Zacuto have done some good stuff because their structure allow them to do so and there is a commercial reason behind also.

Remember the James Russell article on the Leica M9 and the reactions? Completly crazy.
Remember the reactions when Michael said that famous word about the K7 calling it just "competent"? I was absolutly amazed by the forum's reactions.(and I also shoot Pentax and
I saw the same things as Michael saw in his article and did not feel offended because a brand I own does not convince...Pentaxes forums where all in flammes after that, simply hilarious)
etc...

The problem with photography, is that there is a quasi mystic and sexual connection between gear and user. That is why we never see women in those kind of battlefields.
Brands are like the football team we supports so obviously there is an against necessity. It is competition and who's got the biggest one.

This is the tennage age. The differences between women and men, is that in men the teenage age lasts much longuer...

But yes, American girls are easy.
« Last Edit: July 01, 2010, 03:06:10 AM by fredjeang » Logged
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« Reply #88 on: July 01, 2010, 03:17:06 AM »
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Quote from: Steve Hendrix
Yes it's true. US girls are easy.



Steve Hendrix

I have reliable sources who tell me they're easy - as long as you're not yet married to them

Edmund
« Last Edit: July 01, 2010, 03:36:27 AM by eronald » Logged

Edmund Ronald, Ph.D. 
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« Reply #89 on: July 01, 2010, 03:38:38 AM »
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Quote from: dubomac
Let me focus (pun intended) on a single sentence in David's post:

"The stepper motors in the H lenses do not suffer from this issue".

Therefore, according to David, Hasselblad uses stepper motors to focus their lenses.

The definition of a stepper motor is as follows: A stepper motor is a special type of electric motor that moves in increments, or steps, rather than turning smoothly as a conventional motor does.

Therefore, the Hasselblad lenses focus in steps.

I rest my case.

Mark,

EDIT - I apologise but I have made an error.  The Aperture drive uses a stepper motor for precise setting of aperture increments.  The focus drive uses a DC motor.  I had got them mixed up in my old age.

So we can set any distance as described earlier.  Information relayed to me from the product manager.

Apologies to all!


The DC motor in the lens is finite enough for us to be able to set any distance as I stated earlier.  Again, connect an H2/3/4D to Phocus, hit the remote focussing button with the Cmd key applied and you will see exactly how small one click is.

The Leica specialist's quote is 100% correct...

"Reliability is not only one of the major features of the complete S-system but is also a very important point with respect to AF operation. That the S2 AF performance (reliability, speed and precision) is so high has many reasons. It is an advantage to have very small focus steps at distances approaching infinity (where you have the least depth of field), and where the lens has to focus very precisely. The Leica Summarit-S 70mm has a focus resolution of ___ micron (=1 focus step). Furthermore there is a f-stop correction depending on the focus distance. The operating temperature, which also has a big impact on AF precision, is considered as well. But most important is that all lenses and cameras are checked very carefully (and if necessary corrected) by our QA department before they are delivered to our customers. The AF and image sensor planes (CCD) are aligned most precisely. These smallest tolerances are only possible with an integrated digital system! "

Of course they don't reveal what the focus resolution is and I wouldn't expect them too.  Nor do we.  ;-)

Also note he/she says "It is an advantage to have very small focus steps".  Not "Leica has smaller focus steps than anyone else!".  So they are being very honest about their AF description which is nice.

So we can summarise...

1)  Small Focus steps at infinity are an advantage

2)  Aperture dependant focus correction is an advantage

3)  Lenses / Cameras are calibrated for AF accuracy as part of an integrated system

Its nice to see we operate in exactly the same way as Leica.  

The only way to differentiate certain systems is the value/tolerance at which the camera decides it is in focus.  These figures, not available.  The other way is....

At the end of the day the maths is meaningless if a Photographer picks up a camera and says the Hasselblad/Phase/Leica AF sucks/excels in certain conditions.  Period.  If you feel the Leica responded better than other cameras you have used, then I value this opinion more than the science behind it.


I'm sorry Mark, but I still think the wording in your original article is misleading.  You also contradict yourself by saying the lenses have "essentially no focus shift" when the Leica specialist says otherwise.

Best Regards,





David
« Last Edit: July 01, 2010, 04:14:10 AM by David Grover / Hasselblad » Logged

David Grover
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« Reply #90 on: July 01, 2010, 04:33:43 AM »
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Quote from: eronald
I have reliable sources who tell me they're easy - as long as you're not yet married to them

Edmund


they stay easy - even after marriage ...?
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Pieter Kers
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« Reply #91 on: July 01, 2010, 04:37:08 AM »
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Quote from: fredjeang
snip

Don't get me wrong, BC is right in essence. I'm also fed up to see the happy familly kind of pictures that are generally spread over the internet in gear testing.
And it is true that very little if no information is deliver regarding the PP, the tech issues, the tether task etc...
But the problem is exactly what you see here: Even if people would do those testing in BC's minimum standards, they are poorly rewarded.




Am I teasing.  Well sort of, but hey it's a tough job and somebody's got to do it.

Am I serious about seeing better testing photographs, yes, definitely because nothing is a buzz kill when reading about a $50,000 camera system than seeing shots off a roof on a rainy day.

I dig photographs much more than cameras, I like looking at pretty photographs, strange photographs, exceptional photographs and daring photographs.  That's why we buy these things.

Mark and  Guy are probably correct that they're not paid for testing and writing and I don't know the financial aspects of LL or Guy's site, but there has to be more reasons for doing it than just seeing your name in print.

But, don't get me wrong, I liked the article and understand what it is like to be on the sharp point of a stick.  J.R. wrote sumtin' about first time focusing with a range finder and caught a load a c#$p over it, but also received some of the nicest comments about the article he ever received.  (At least that's what he told me).  insert one of those silly smiley faces here.

But J.R. took the Leica out of the box and shot an editorial spread with it.  Not completely and there were other cameras used and a whole bunch of backups, but it was put into a professional setting and I (uh excuse me J.R.) learned bunches from that experience.

So if there is a reason I post, other than to give myself a break from rendering video, doing an estimate to version 5 or negotiating reuse for the 12th time, it's to try to make the point that these cameras are made to take pretty photographs, not color charts.

You could hand that Leica off to my friends gwitif, or rogan, or a whole bunch of photographers I know that could really put it through it's paces and turn something that would be noteworthy.  (I'm not saying Mark can't either, so don't read me wrong).

Now the downside to this is if rogan finds it takes 3 hours for the previews to pop up when tethering, or gwitif sees purple ca on any backlit object, they're gonna say it, cause that's the kind of people they are, but then again that's what should be reported the good and the need to be fixed bad.

Anyway, I would think it would be in the camera makers best interest to try this route.

IMO

P.S.  

In regards to focus, it's all subject dependent, but I can promise you no large body of work is ever shot without some missed focus, at least with mechanical cameras, maybe Pixtar doesn't have those issues, but we do.

Best,

BC
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BartvanderWolf
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« Reply #92 on: July 01, 2010, 05:37:30 AM »
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Quote from: Rob C
Quote
It is an advantage to have very small focus steps at distances approaching infinity (where you have the least depth of field), and where the lens has to focus very precisely.

Isn't there something a little skewed about this statement?

Yes!

Perhaps he intended to say that a small step in the focus motor results in a large difference in subject focus distance. However, at the same time DOF is relatively huge in absolute terms when focussing near infinity. What's more, a sensor array with sensels of finite dimensions has a hard maximum resolution limit, and thus resulting DOF. The combination of a little diffraction wide open and sensel surface area will make it impossible to discriminate between focus positions within a certain 'DOF zone', which happens to be huge near infinity.

Cheers,
Bart
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« Reply #93 on: July 01, 2010, 06:27:26 AM »
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David,
 
 All of this leads me to ask YOU directly a question which has always puzzled me:
 
 How does Hasselblad ensure that the MANUAL focus is accurate?

 I would appreciate an informative answer or else a refusal to answer, but no Leicaish boilerplate.

Edmund

Quote from: David Grover / Hasselblad
Mark,

EDIT - I apologise but I have made an error.  The Aperture drive uses a stepper motor for precise setting of aperture increments.  The focus drive uses a DC motor.  I had got them mixed up in my old age.

So we can set any distance as described earlier.  Information relayed to me from the product manager.

Apologies to all!


The DC motor in the lens is finite enough for us to be able to set any distance as I stated earlier.  Again, connect an H2/3/4D to Phocus, hit the remote focussing button with the Cmd key applied and you will see exactly how small one click is.

The Leica specialist's quote is 100% correct...

"Reliability is not only one of the major features of the complete S-system but is also a very important point with respect to AF operation. That the S2 AF performance (reliability, speed and precision) is so high has many reasons. It is an advantage to have very small focus steps at distances approaching infinity (where you have the least depth of field), and where the lens has to focus very precisely. The Leica Summarit-S 70mm has a focus resolution of ___ micron (=1 focus step). Furthermore there is a f-stop correction depending on the focus distance. The operating temperature, which also has a big impact on AF precision, is considered as well. But most important is that all lenses and cameras are checked very carefully (and if necessary corrected) by our QA department before they are delivered to our customers. The AF and image sensor planes (CCD) are aligned most precisely. These smallest tolerances are only possible with an integrated digital system! "

Of course they don't reveal what the focus resolution is and I wouldn't expect them too.  Nor do we.  ;-)

Also note he/she says "It is an advantage to have very small focus steps".  Not "Leica has smaller focus steps than anyone else!".  So they are being very honest about their AF description which is nice.

So we can summarise...

1)  Small Focus steps at infinity are an advantage

2)  Aperture dependant focus correction is an advantage

3)  Lenses / Cameras are calibrated for AF accuracy as part of an integrated system

Its nice to see we operate in exactly the same way as Leica.  

The only way to differentiate certain systems is the value/tolerance at which the camera decides it is in focus.  These figures, not available.  The other way is....

At the end of the day the maths is meaningless if a Photographer picks up a camera and says the Hasselblad/Phase/Leica AF sucks/excels in certain conditions.  Period.  If you feel the Leica responded better than other cameras you have used, then I value this opinion more than the science behind it.


I'm sorry Mark, but I still think the wording in your original article is misleading.  You also contradict yourself by saying the lenses have "essentially no focus shift" when the Leica specialist says otherwise.

Best Regards,





David
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Edmund Ronald, Ph.D. 
David Grover / Phase One
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« Reply #94 on: July 01, 2010, 06:50:09 AM »
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Quote from: eronald
David,
 
 All of this leads me to ask YOU directly a question which has always puzzled me:
 
 How does Hasselblad ensure that the MANUAL focus is accurate?

 I would appreciate an informative answer or else a refusal to answer, but no Leicaish boilerplate.

Edmund

I refuse!  ;-)

Well, I guess we can't ensure manual focus is accurate.  If you use the focus indicator lights in the viewfinder this is using the Phase Detection hardware to 'tell' you when the subject in the crosshairs is in focus.

Aperture dependant focus corrections are not made when in MF mode as I would imagine most photographers would be quite upset if the camera starting shifting the lens if you had purposely disabled it.

Perhaps though some functionality of being able to indicate an aperture focus correction could be useful.  But I would imagine most customers would prefer we don't interfere, if the camera is set to manual.

David



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« Reply #95 on: July 01, 2010, 06:58:06 AM »
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Quote from: David Grover / Hasselblad
I refuse!  ;-)

Well, I guess we can't ensure manual focus is accurate.  If you use the focus indicator lights in the viewfinder this is using the Phase Detection hardware to 'tell' you when the subject in the crosshairs is in focus.

Aperture dependant focus corrections are not made when in MF mode as I would imagine most photographers would be quite upset if the camera starting shifting the lens if you had purposely disabled it.

Perhaps though some functionality of being able to indicate an aperture focus correction could be useful.  But I would imagine most customers would prefer we don't interfere, if the camera is set to manual.

David


 and while we know about the careful check of the lens-sensor distance, and the check of the lens-AF sensor distance, what about a check of the optical path to the viewfinder?
 shall we assume that precise MF is simply unsupported?

Edmund
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« Reply #96 on: July 01, 2010, 07:56:17 AM »
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Quote from: bcooter
Am I teasing.  Well sort of, but hey it's a tough job and somebody's got to do it.

Am I serious about seeing better testing photographs, yes, definitely because nothing is a buzz kill when reading about a $50,000 camera system than seeing shots off a roof on a rainy day.

I dig photographs much more than cameras, I like looking at pretty photographs, strange photographs, exceptional photographs and daring photographs.  That's why we buy these things.

Mark and  Guy are probably correct that they're not paid for testing and writing and I don't know the financial aspects of LL or Guy's site, but there has to be more reasons for doing it than just seeing your name in print.

But, don't get me wrong, I liked the article and understand what it is like to be on the sharp point of a stick.  J.R. wrote sumtin' about first time focusing with a range finder and caught a load a c#$p over it, but also received some of the nicest comments about the article he ever received.  (At least that's what he told me).  insert one of those silly smiley faces here.

But J.R. took the Leica out of the box and shot an editorial spread with it.  Not completely and there were other cameras used and a whole bunch of backups, but it was put into a professional setting and I (uh excuse me J.R.) learned bunches from that experience.

So if there is a reason I post, other than to give myself a break from rendering video, doing an estimate to version 5 or negotiating reuse for the 12th time, it's to try to make the point that these cameras are made to take pretty photographs, not color charts.

You could hand that Leica off to my friends gwitif, or rogan, or a whole bunch of photographers I know that could really put it through it's paces and turn something that would be noteworthy.  (I'm not saying Mark can't either, so don't read me wrong).

Now the downside to this is if rogan finds it takes 3 hours for the previews to pop up when tethering, or gwitif sees purple ca on any backlit object, they're gonna say it, cause that's the kind of people they are, but then again that's what should be reported the good and the need to be fixed bad.

Anyway, I would think it would be in the camera makers best interest to try this route.

IMO

P.S.  

In regards to focus, it's all subject dependent, but I can promise you no large body of work is ever shot without some missed focus, at least with mechanical cameras, maybe Pixtar doesn't have those issues, but we do.

Best,

BC


Alright tethered . The S2 sucks and i did not even bother after reading Michael mentioning it took forever to get a preview. With paid models on my set it was not worth the time to even bother. I admit it was not my focus of attention. P40+ is a whole different kettle of fish. I have said several time 2 second preview , has never crashed even going very fast as the strobes will allow and sensor plus is even faster. Yes you can turn camera off and on and not lose the tethering or rebooting of program and pulling cord I was able to immediately connect again. My only problem I have had and I think it is more my computer or the firewire cable itself is on initial plugin of firewire cable the software is not seeing the connection without a restart. That is not a software issue or C1 in this case but my belief a faulty Firewire 800 cable and that is something I want to sort out.
Now every reviewer also wants to get out and shoot so not every aspect of a cam is covered. Some technical things where discussed in other reports and given the time we have than some of us leave certain things out so we can get to other area's that we feel important. Yes Jack and I are for sure guilty of that , our goal was to shoot in some varied settings that have not been done. Models for one in the brightest light around here in Arizona was a big one for me that we wanted to see how these cams can handle that type of light range and only did some stuff with lighting because others where doing that. Admittedly we where cherry picking for different situations to show what range these cams had and did not shoot somethings as others have. Given the time we had it was our best call. I am sure others also did this as well to fit there work and desire to test different things.

Now I don't know about anyone else but our forum makes no money from anything except workshops themselves. No banner ads and such and we have enjoyed that advertising free setting and more importantly we do these out of the love of photography and also to help our readers understand these systems better. Frankly we owe nothing to anyone and no one pays us for that data. Call us all good guys willing to help others if you will but sure in the end we hope people will come to a workshop and learn more. I can't sit here and say differently and won't. I freely admit GM Photography is for commerce and GetDPI is my love. Anyone want to throw rocks at that go right ahead but the folks you have mentioned can get demo's of this gear anytime you want and if not let me know and I can help arrange those demo's if your serious about a future purchase, I'm not going to waste people's time on that just for curiosity sake. There are dealers here and our place that can certainly help people send them a PM and they will help, in the end they are all really nice folks and I have met a lot of them. Now I am not going to defend any review I do as it is what it is and I provide the raws for folks to test the files themselves all free and everyones reviews are all free. Like Fred said we are not crazy about the rocks thrown but are willing to still do these in spite of it and that I know I can speak for everyone that does them. Name in print is meaningless so let's not go there, end of day we love photography plain and simple. After 35 years it's my whole life I better freaking love it just like a marriage or we are in trouble . Now honestly a lot of images may not be pretty but you can gain information from them and really that all that counts. If you can't get what you want from them than do a demo but please don't ever say to me you are too busy, so am I and we have families to care for as well and also our commerce daily routine.

My last comment and I think I can speak for the folks that do these reviews is we try to do the best we can and we will make mistakes along the way no doubt we are only human but at least we are doing them and trying to help others. If not than we are back to the old days with no data and you put down your 50 k and than suck air because it is not what your really wanted because no data was around to help you. You can love us , hate us but end of day you need us. End of my early morning comments and off to more espresso.
Pardon the typos if any not looking back to fix them. Off for another round of chemo for my wife
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« Reply #97 on: July 01, 2010, 08:00:53 AM »
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Quote from: eronald
and while we know about the careful check of the lens-sensor distance, and the check of the lens-AF sensor distance, what about a check of the optical path to the viewfinder?
 shall we assume that precise MF is simply unsupported?

Edmund

No.

Mirror is also adjusted to the focussing screen on a per camera basis.

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« Reply #98 on: July 01, 2010, 09:02:27 AM »
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Quote from: David Grover / Hasselblad
No.

Mirror is also adjusted to the focussing screen on a per camera basis.



Isn't it incredible? That would have been the very first thing that I would have taken for granted with absolutely any reflex camera! Please don't tell me that because of the af and now digital age you are unique in checking these things out - please?

Rob C
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« Reply #99 on: July 01, 2010, 09:22:45 AM »
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Quote from: dubomac
Here is the quote:

"Reliability is not only one of the major features of the complete S-system but is also a very important point with respect to AF operation. That the S2 AF performance (reliability, speed and precision) is so high has many reasons. It is an advantage to have very small focus steps at distances approaching infinity (where you have the least depth of field), and where the lens has to focus very precisely. The Leica Summarit-S 70mm has a focus resolution of ___ micron (=1 focus step). Furthermore there is a f-stop correction depending on the focus distance. The operating temperature, which also has a big impact on AF precision, is considered as well. But most important is that all lenses and cameras are checked very carefully (and if necessary corrected) by our QA department before they are delivered to our customers. The AF and image sensor planes (CCD) are aligned most precisely. These smallest tolerances are only possible with an integrated digital system! "

Mark Dubovoy

Mark,

I enjoyed your article and accepted your observation that autofocus of the S2 was very accurate. While the theory (steps vs continuous focusing) is interesting, the observation is not affected by the theory. I am surprised that your German expert states that the depth of field is least at subject distances approaching infinity. I think he should have used depth of focus, not depth of field. Depth of focus can be calculated: t = 1*N*c*(v/f), where t is the depth of focus, N the f/number, v the image distance, and f is the lens focal length. With a subject distance of infinity, v = f and t is at its minimum. With less subject distances, you have to rack out the lens, increasing v and thus the depth of focus (t). As all photographers know, depth of field is less with closeups.

That the smallest tolerances are possible only with integrated systems are borne out by Joseph Holmes experiences with various MFDBs (cited above).

Because of focus shift when stopping down and imprecision in AF sensor and image planes, the best focus with dSLRs is obtained with live view. Does the S2 have this?

Regards,

Bill

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