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Author Topic: Mark Dubovoy's Leica S2 Review  (Read 18670 times)
BernardLanguillier
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« Reply #100 on: July 01, 2010, 09:55:39 AM »
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Quote from: bjanes
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?

Who would have thought even 3 years ago that the ability to generate a live stream from a sensor would get on the critical path of image quality?

That single shortcoming though is the main reason why I am not seriously considering buying a Pentax 645D. The good news being that I might devote the cash on something real useful instead... like a new pair of speakers?

Cheers,
Bernard
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A few images online here!
BernardLanguillier
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« Reply #101 on: July 01, 2010, 09:58:29 AM »
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Quote from: kers
they stay easy - even after marriage ...?

Can we talk about the discrete nature of autofocus please?  
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A few images online here!
BernardLanguillier
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« Reply #102 on: July 01, 2010, 10:00:15 AM »
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Quote from: SeanBK
Congratulations Bernard & wish you many joys outside of our L-L bubble.

Thks Sean, it would indeed seem that this a life outside.  

Cheers,
Bernard
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A few images online here!
David Grover / Phase One
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« Reply #103 on: July 01, 2010, 10:02:12 AM »
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Quote from: Rob C
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

I would imagine this is common practice.
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David Grover
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wildlightphoto
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« Reply #104 on: July 01, 2010, 10:04:59 AM »
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Quote from: Rob C
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

It's not something you should take for granted with reflex cameras near the lower end of the price scale.
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eronald
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« Reply #105 on: July 01, 2010, 10:13:26 AM »
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Quote from: telyt
It's not something you should take for granted with reflex cameras near the lower end of the price scale.

And then there is wear and tear in the field. Bounce a mirror 50K times ....

Edmund
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BartvanderWolf
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« Reply #106 on: July 01, 2010, 10:17:59 AM »
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Quote from: bjanes
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.

Hi Bill,

That sounds like a plausible explanation, because the statement as originally made didn't make sense.

Too bad the quote
Quote
The Leica Summarit-S 70mm has a focus resolution of ___ micron (=1 focus step).
lost it's crucial bit of information, the number of microns focus resolution. If small enough it wouldn't matter whether a stepper motor was used or a DC motor.

Cheers,
Bart
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dubomac
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« Reply #107 on: July 01, 2010, 12:58:06 PM »
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Sorry David, but it is you who is incorrect again.

There is nothing in the "Leica specialist" (as you call him) part of the quote that I shared with the group regarding focus shift. You might be confused with the wording about an F/stop correction, which is something completely different.

In fact, the more complete quote is as follows:

"The prerequisite for the highest image quality is represented by the S-lenses – the key competence of Leica. Let’s have a look at the MTF curves (available on the Leica S Microsite). I think the facts speak for themselves. Highest optical performance is provided at full stop, from the close-up limit to infinity. There is no focus-shift while stopping down due to flowting lens elements. Additionally the use of the best available types of glass and aspherical / apochromatical designs minimize optical abberations. There is no need for time and money wasting software corrections.
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."

And goes on from there.

Please pay attention to the sentence "there is no focus shift while stopping down...."  (sorry, he is German and misspelled the word "floating"). Read it again.  He does not say "minima"l or "small" focus shift;  he says "no focus shift".  Coming from a company as conservative as Leica, this is quite a strong statement.

I have a slight suspicion that you did not like my article. ..

:-)

However, as I said before, I stand 100% behind everything I said in the article.  All the information is factually and technically correct.

I have nothing else to say, and therefore, this is my last post on this thread.

Best regards,

Mark
 

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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David Grover / Phase One
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« Reply #108 on: July 01, 2010, 01:34:06 PM »
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Quote from: dubomac
I have a slight suspicion that you did not like my article. ..

:-)

However, as I said before, I stand 100% behind everything I said in the article.  All the information is factually and technically correct.

I have nothing else to say, and therefore, this is my last post on this thread.

Best regards,

Mark

Mark,

The only thing I didn't like about your article is the incorrect information regarding Hasselblad and also the wording you use to describe Phase Detection AF.

If you feel the S2 gave you the best AF experience then it is not for me to argue.

I still disagree with some of your statements so, I will guess we will agree to disagree and all be happy.

Best Regards,



David




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David Grover
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Dale Allyn
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« Reply #109 on: July 01, 2010, 02:15:38 PM »
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Quote from: bcooter
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 like looking at pretty photographs, strange photographs, exceptional photographs and daring photographs.  That's why we buy these things.

Strongly Agree! Sure, at first a few quick snaps and shots of brick walls are expected, but beautiful or interesting images are what many of us seek. Masterpieces, all? Of course not. They don't happen on demand. But interesting? Yes please. I always appreciate when those sharing results from these various cameras have an opportunity to actually shoot subjects as they would when making "real" images.

I don't intend this as a comment in reference to Marks article, only in a very general sense for the process overall. Thanks, B.C. (and alter ego) for bringing this up.

Cheers!
« Last Edit: July 01, 2010, 02:33:03 PM by DFAllyn » Logged

eronald
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« Reply #110 on: July 01, 2010, 02:47:49 PM »
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Quote from: DFAllyn
Strongly Agree! Sure, at first a few quick snaps and shots of brick walls are expected, but beautiful or interesting images are what many of us seek. Masterpieces, all? Of course not. They don't happen on demand. But interesting? Yes please. I always appreciate when those sharing results from these various cameras have an opportunity to actually shoot subjects as they would when making "real" images.

I don't intend this as a comment in reference to Marks article, only in a very general sense for the process overall. Thanks, B.C. (and alter ego) for bringing this up.

Cheers!

A fashion photographer who used to be on RG and has been seen here at times sent me some Raws, when I was deciding to buy a back. I cannot name the guy, besides he seems to change names every day, but I'm really thankful for that.  His images were breathtaking, and they also clearly showed me what I could expect from this type of product if used with studio flash. Also these images were much more useful to me than anything available from the manufacturers.

Edmund
« Last Edit: July 01, 2010, 02:49:47 PM by eronald » Logged
ErikKaffehr
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« Reply #111 on: July 01, 2010, 03:17:10 PM »
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Hi,

One of the reasons microfocus adjustment is a good thing.

Best reagrds
Erik

Quote from: eronald
And then there is wear and tear in the field. Bounce a mirror 50K times ....

Edmund
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Rob C
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« Reply #112 on: July 01, 2010, 04:14:39 PM »
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Well, we certainly didn't clear up the little matter of depth of field at infinity!

The truth of what he was really thinking about, I imagine, is that because the depth of field is so wide at/near infinity, it becomes progressively more difficult for eye or machine to nail the precise plane of focus where it is so dificult to discern subtle differences.

Depth of focus: that 's a measurement that belongs at the film/sensor plane and has nothing to do with anything here, other than the fact that the longer the lens the deeper the depth of focus and the wider the lens the more shallow. You will discover that with your first trip into LF Land, if not LuLaLand!

God, it's hot in this stuffy room. I need a shower, feel a bit hungry but won't eat anything because it's too close to bedtime and I suffer from acid indigestion which threatens to choke me now and again when I forget and eat late. And to think, I used to be able to work until midnight, come home, devour a steak, french fries, peas, whatever else was going, go up to bed, do a hundred-and-twenty to a hundred-and-thirty press-ups and be up again in the morning for breakfast and in time to drive the kids to school. I can no longer do one press-up, I suspect, and am too scared to try. How time mocks us.

Rob C
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john milich
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« Reply #113 on: July 01, 2010, 04:52:11 PM »
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"...there is a f-stop correction depending on the focus distance."

this is interesting.  since f-stop is defined by focal length/aperture diameter, are they making a slight aperture adjustment with respect to distance to compensate for the changing distance from lens center to image plane affecting exposure, like you do with a bellows extension?
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bjanes
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« Reply #114 on: July 01, 2010, 05:21:48 PM »
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Quote from: Rob C
Well, we certainly didn't clear up the little matter of depth of field at infinity!

The truth of what he was really thinking about, I imagine, is that because the depth of field is so wide at/near infinity, it becomes progressively more difficult for eye or machine to nail the precise plane of focus where it is so dificult to discern subtle differences.

Depth of focus: that 's a measurement that belongs at the film/sensor plane and has nothing to do with anything here, other than the fact that the longer the lens the deeper the depth of focus and the wider the lens the more shallow. You will discover that with your first trip into LF Land, if not LuLaLand!

On the contrary, the depth of focus is critical to this discussion. For critical work, the plane of the image has to coincide with that of the sensor and also that of the focusing plane. The depth of focus gives a bit of tolerance. When you are focusing using the viewfinder and the focusing screen, the placement and alignment of this screen as well as the reflex mirror are critical, or else the image on which you are focusing will not represent the focus in the plane of the sensor. With Nikon dSLRs, the phase focusing detection autofocus sensors are in the bottom of the mirror well and the same considerations apply to these sensors as to the focusing screen.

When the object distance is relatively great, the depth of focus, t, is 2 * N * c, where N is the f/number and c the circle of confusion. If you use the commonly accepted (and liberal) circles of confusion of 0.029 mm and 0.047 mm for 35 mm and 645 (6 x 4.5 cm), the depth of focus is 0.23 and 0.38 mm respectively for f/4. The alignment of the lens must also be perfectly perpendicular to the sensor plane. With silver halide photography, the flatness of the film emulsion is also critical.

Regards,

Bill
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michael
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« Reply #115 on: July 01, 2010, 05:34:32 PM »
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I think that this thread how now run its course. It's become too long, and crosses over into multiple topics.

I am therefore closing it, but if the topic continues to intrigue you, please feel free to start a new one.

Michael
« Last Edit: July 01, 2010, 05:35:22 PM by michael » Logged
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