Ad
Ad
Ad
Pages: « 1 [2] 3 4 »   Bottom of Page
Print
Author Topic: New Leica Digicam  (Read 16332 times)
Scott_H
Sr. Member
****
Offline Offline

Posts: 331


« Reply #20 on: December 04, 2003, 07:48:21 AM »
ReplyReply

For a smaller sensor the actual focal length is shorter than than it would be for a larger sensor.
Logged

Ray
Sr. Member
****
Offline Offline

Posts: 8939


« Reply #21 on: December 05, 2003, 12:42:17 AM »
ReplyReply

Quote
Agreed, with one crucial qualification: shifting to a larger format only fully gives this advantage when it allows one to gather more light, through some combination of larger aperture diameters (less DoF etc.) and longer exposure times that would not possible in the smaller format because it would lead to overexposure.
  
BJL,
But isn't this exactly what happens? The larger the format, the larger the f stop number required, the longer the exposure required and the greater the need for a tripod. It's all very cumbersome and only for the truly dedicated.

Each format has its advantages and disadvantages but one should not forget that large format cameras usually have a tilt mechanism which allows the use of larger apertures whilst maintaining a reasonable DoF. I believe f 22 is the aperture required for stunningly sharp and detailed landscapes from a 10x8" camera.

Of course, one could argue that tilt mechanisms are also available for some of the smaller formats. I own a 35mm tilt&shift lens myself, but I don't see any resolution advantage to the larger apertures. 35mm lenses in general tend to have their best performance at either f8 or one or two stops down from maximum aperture. I suppose it's possible to design, say an f2.8 lens that has its best performance at full aperture, but such performance is likely to be only marginally better than at f 8.

What would be required for a small digicam to compete with a full frame 35mm, irrespective of the number of pixels on the sensor, is an F 2.8 lens that has significantly better resolution at F 2.8 than the larger format 35mm lens has at f8.

Is this possible? Well, it might be some day. But aren't we talking Science Fiction?  Cheesy
Logged
BJL
Sr. Member
****
Offline Offline

Posts: 5171


« Reply #22 on: December 05, 2003, 08:39:37 AM »
ReplyReply

Ray,
    as far as I can tell, everything you say is true about the optical relationships between focal length, image size formed in the camera (and so indirectly, camera format), aperture diameter, aperture ratio, and subject distance. However, I seriously doubt the relevance of your comparisons in most situations. I agree that they do apply sometimes, such as for the unfortunate photographer who has an "APS" format DSLR, wants to take wide angle images, but is still making do with a collection of 35mm format lenses!

   The options you describe involve the photographer who is using a smaller format either (a) moving back, in order to use the same lens instead of a shorter focal length lens that would often be smaller and lighter, or ( using a smaller aperture ratio, perhaps in order to use the same shutter speed instead of a using a faster one. Neither seems like the first or second choice in most situations!
   Indeed, photographers moving down in film format size have very rarely used either of those strategies: instead, the primary change has always been seeking roughly the same composition (perspective, depth of field, and even degree of diffraction limitation) by moving to a shorter focal length, proportionately lower aperture ratio (same aperture diameter), and hence some combination of higher shutter speed and lower speed film (or lower sensor "ISO" sensitivity setting).

   Why not compare on the basis of what photographers have actually been observed to do in most cases over the years?

   A final note: the most extremely shallow DOF I have seen in film photography usually comes from the smallest mainstream film format, in things like portraits done with ultra-fast 35mm format lenses.
Logged
victoraberdeen
Full Member
***
Offline Offline

Posts: 205



WWW
« Reply #23 on: December 05, 2003, 11:51:34 PM »
ReplyReply

For you folk who are getting excited about DoF, take a look at the DOF notes on Bob Wheeler's site, it is a very good explanation. notes on technical aspects of photography

Enjoy

Victor
Logged
victoraberdeen
Full Member
***
Offline Offline

Posts: 205



WWW
« Reply #24 on: December 07, 2003, 08:38:05 PM »
ReplyReply

Sorry Ray your writing is just not clear. Please don’t expect me to take the rap for the commentary of others! This is a simple subject explained very well in Rob’s article.

Now the 'angle of view' is a good example of poor vocabulary, do you mean the perpendicular angle of the image plane to the subject or how many degrees the lens sees. The first one is correct, the number of degrees a lens captures to an image plane is the field of view.

Funny thing, to understand this subject you need drawings the like of Rob’s!

Now Ray save us folk from your rant and crawl back in to your f32!
 
Logged
BJL
Sr. Member
****
Offline Offline

Posts: 5171


« Reply #25 on: December 09, 2003, 06:16:05 PM »
ReplyReply

Quote
a) If, however you want the subject to have the same percentage size in the image, you’ll need to use different lenses and for the same depth of field range a different aperture.

...

 it is the wrong reason to choose your format.
Point a) is exactly what I am banging on about: larger formats will require larger aperture ratios to get the same depth of field with teh same framing, tending to force the use of longer exposure times when the opportunities for increasing ISO run out, which is less convenient for many moving subjects and some hand-holding situations

Point  is mysterious; I would think that in many photographic situations, the ability to operate at higher shutter speeds is often a very good reason to use smaller formats, for greater hand-holdability to start with. In the film world, action photography (be it sports, wildlife or available light people photography) highly favours 35mm over larger formats for very much these sort of reasons, and lots of sport/action photographers are now enamoured of the advantages of the even smaller APS DSLR formats over 35mm DSLR's for what I believe are related reasons.

   Anyway, I was not arguing that people should choose one format or another; I simply made a comment about what people should expect, and not expect, of the new smaller digital formats, in comparison to the more traditional, familiar larger formats.

   That, and debunking the idea that very different format sizes should be compared on the assumption of using roughly the same f-stop when trying to get a similar image, which you iterate again in your opening paragraph suggestion about f/5.6 working well regardless of format.
Logged
Ray
Guest
« Reply #26 on: December 10, 2003, 12:41:26 AM »
ReplyReply

Quote
Ray, No assumption, the focal length needs to be the same.
The Leica Digicam has a 7mm-22.5mm zoom. The 2/3rds format (a silly term really) has a sensor diagonal of 11mm, equivalent to a 35mm format lens of 44mm. The equivalent f stop in the Leica for approx. same DoF as 35mm at f 5.6 (all else equal) would be F1.4, so even if I wanted to maintain the same DoF, I wouldn't be able to. Maximum aperture on the Leica is F2.

You might well ask, so what! And it's true that the resolution limitations of the really small format camera could make the camera useless for one's purposes. A pinhole camera has phenomenal DoF and you maight say, so what!, everything's slightly blurry, and you'd be right. It definitely wouldn't be suitable for magazine coverage.

But this is a different issue, isn't it? We're having a theoretical discussion here, aren't we? The subject is not, "How to make interesting photos by judicious use of DoF", or "How to make a million bucks by selling photos".
Logged
Robert Roaldi
Guest
« Reply #27 on: December 11, 2003, 07:52:48 AM »
ReplyReply

I may be mistaken but I believe the chip designations come from the silicone chip world. They have their own way of naming and describing things. The fact that they have little relevance to photographers is to be expected. They still talk about furlongs at horse race tracks.
Logged
twokids
Guest
« Reply #28 on: May 07, 2004, 02:25:42 AM »
ReplyReply

Philibileboiles a word...  :angry:  :p  :O  Cheesy  :cool:
Logged
Guest
« Reply #29 on: December 01, 2003, 11:04:21 AM »
ReplyReply

It also has small 3.4 micron pixels and uses SD cards.  

I had to laugh at the Leica PR writer that penned "Extra large picture storage card with 64 MB ".

Right. It'll hold 6 pictures in RAW mode.

All of that aside, it does look very appealing, and if they get all of the pieces to come together properly it could well be an attractive digicam.

A digital M series Leica it's not though, regardless of the cosmetics.

Michael
Logged
Ray
Sr. Member
****
Offline Offline

Posts: 8939


« Reply #30 on: December 03, 2003, 06:30:56 PM »
ReplyReply

BJL,
I see you haven't lost your enthusiasm for the smaller format.  Cheesy

It's a bit of an effort to follow your reasoning, but it seems to me you are essentially saying the smaller format has the advantage of smaller f stop numbers and faster shutter speeds for an equivalent DoF. I think this principle applies across all formats from a 16x20" field camera to the most miniature digicam.

However, there is an unavoidable trade-off. The smaller the format, the smaller the maximum print size in relation to a given standard of acceptable sharpness and the narrower the range of DoF settings (for acceptable sharpness). I see no way around this. Whilst advances in technology will no doubt eke out greater performance (lower noise and higher resolution) from the smaller digicam, such advances should also be able to be applied to the larger formats, thus maintaining those advantages of the larger format.

We should not lose sight of the fact that these small format digicams like the new Leica and the Canon G4 etc bear the same relationship to full frame 35mm as 35mm does to LF 4"x5".
Logged
Craig Jones
Guest
« Reply #31 on: December 04, 2003, 07:46:45 AM »
ReplyReply

Quote
However, if you want to maintain the same angle of view from the same shooting position, DoF increases, for any given f stop, as the sensor size decreases.
That's because when you adjusted the focal length, you changed the physical aperture to keep the f-number constant.  DOF didn't increase because of the smaller sensor, it increased because you closed the physical aperture!

Quote
Increasing the aperture (reducing the f stop number) always increases the amount of light passing through a lens. However, it's only the small format camera that can offer a good DoF at those larger apertures. The advantage of this is, for the same scene and angle of view, one can use, say F 2 at ISO 100 and 1/125th sec instead of F 8 at ISO 400 and 1/60th sec.

This is an example of the typical confusion between aperture and f-number.  When comparing different format sizes, you must compare like physical apertures, not like f-numbers, when discussing DOF.  Small format cameras do not offer "good DoF at those larger apertures" but they do offer "good DoF" at lower f-numbers since a given physical aperture represents a lower f-number on the smaller format.

People get away with linking aperture and f-number because they are used to dealing within the same format.  When comparing different formats, you must be more careful.  The DOF myth is due to lack of rigor.

DOF is a function of physical aperture and magnifcation.  Ignoring lens performance, smaller formats offer slightly inferior DOF at equivalent, high magnifications.  Exactly the opposite of what is commonly believed.
Logged
BJL
Sr. Member
****
Offline Offline

Posts: 5171


« Reply #32 on: December 04, 2003, 12:20:49 PM »
ReplyReply

pmkierst,

    Depth of field choice is a significant part of desired composition, and the choice will tend to be the same regardless of format used; a particular numerical value of the f-stop used is not an inherent compositional choice. So it seems an outright contradiction to say that "you will still have more DoF for your desired composition on the small sensor camera."

   It is rather obvious that people do NOT use the same aperture ratio when working in different formats, and lenses for different formats do not even offer the same choices of aperture ratio. Many lenses for 4x5 do not even get as wide open as f/8, whereas their counterparts for 35mm and smaller formats often go down below f/2. Indeed, larger format lenses do not offer such low f-stops as 35mm lenses because they would be huge, heavy and give ridiculously little DOF.
Logged
Ray
Sr. Member
****
Offline Offline

Posts: 8939


« Reply #33 on: December 04, 2003, 11:17:07 PM »
ReplyReply

Quote
You need to understand that holding the f-number constant across formats is meaningless and bogus.  Once you figure that out, you'll realize the DOF claim is wrong.
Dear me! I don't quite know what to say, Craig!  Cheesy  What sort of nonsense are you trying to perpetrate!  Huh

The F stop is one of the great concepts of Photography precisely because it is[/i] meaningful across formats. A 300mm lens at f8 will always require the same shutter speed in the same lighting conditions whether that lens is attached to a 35mm camera, a tiny digicam or a 12"x16" field camera, and it will always produce the same DoF from the same shooting position.

I've already mentioned in my response to Victor that 'only' changing the sensor size does not affect DoF. But you must realize that nobody designs and manufactures camera lenses without regard to the sensor size, film size, ie. format of camera the lens will be used with. However, it's true that lenses designed for a larger format can be and sometimes are used for a smaller format, the obvious example being the recent crop of DSLRs such as the D60, 10D and 300D.

So let's look at what happens when we take identical shots from the same position with a 50mm lens on a 1Ds and 10D. If the lens is the same and the F stop is the same and the distance to the central subject is the same . . . it follows that the exposure will be the same and the DoF will be the same. That's the beauty of the F stop system.

But something will be different, won't it? The 10D shot will be severely cropped. In oder to get the same angle of view with the 10D I'll have to step back a few paces. Consequently, the DoF will now be greater on the 10D shot because I've increased the distance between camera and subject. Alternatively, I could just whack on a 28mm lens to get the same field of view from the same position. That would also have the effect of increasing DoF for the 10D shot (at the same aperture).

Now you could argue that the increased DoF that the smaller format 10D seems to exhibit has nothing to do with its smaller sensor size and that the real reason for the increased DoF is the fact that you either (a) had to step back to get a wider FoV or ( had to use a wider angle lens.

However, there are reasons behind reasons. If the 10D did not have a smaller size sensor than the 1Ds, there would be no reason to step back or to fit a wider angle lens. In this example (which extends across all formats), the size of the sensor could be viewed as the more 'primary' cause of the increased DoF.

Even from a purely mathematical point of view, there is a connection between sensor size, F stop and aperture if we're talking about standards lenses for the different formats. F stop is a relationship between the focal length of a lens and the physical dimensions of the aperture (F=FL/D). The focal length of a standard lens (as opposed to a telephoto or wide angle lens) is given by the diameter of the image circle the lens throws on the sensor. The size of the sensor or format bears a very direct relationship to the image circle. All 35mm lenses for example are designed to have an image circle a bit larger than the diagonal of the 36x24mm frame (about 43mm). The diagonal of an 8"x10" plate for a field camera is about 12.8"= 320mm. It's no accident that the standard lens for an 8x10 field camera is just that . . . 320mm.

Get my point?  Smiley
Logged
Craig Jones
Guest
« Reply #34 on: December 05, 2003, 03:00:12 AM »
ReplyReply

Quote
OK, "F-Stop" numbers are dependent on focal length and physical aperture (and it is a non-obvious equation depending on exactly where the actual physical device is located). So saying F/8 for one lens and F/8 for another (different focal length) lens already accounts for the difference.
No it does not.  Physical apertures are normalized by focal length for exposure purposes, not DOF.  Two lenses of different focal lengths at f/8 have different apertures, not the same!  The do, however, works the same way from an exposure point of view.

This fact, which few seem to understand, is why smaller sensors are preceived to have better DOF when they do not.  

Your MF comments simply reflect the fact that MF is not optimized for high magnifications.  It is not a testament to MF's inherent inability to deliver good DOF.  If the lenses were made for it, things would be different.  That's why I used FF 35mm for the macro discussion.  It doesn't help to talk theoretically when you can test.
Logged
Craig Jones
Guest
« Reply #35 on: December 05, 2003, 08:57:54 AM »
ReplyReply

Ray, if you're trying to be helpful by accusing me of spreading nonsense and posting to show off my knowledge, it sure doesn't make you look good.  I noticed you didn't refute anything I said.   Everything I said was correct and you apparently know that already.

This statement:
Quote
However, if you want to maintain the same angle of view from the same shooting position, DoF increases, for any given f stop, as the sensor size decreases.
is correct and I never questioned it or even commented on it. Your quotes that I did comment on were specifically provided.

In your example, the smaller format achieves better DOF by reducing magnification and closing the physical aperture.  The second half of that is cleverly hidden within the "same f-stop" setting since you reduced the focal length.  The resultant improvement in DOF in this test is not due to the change in sensor size, but you know that already since I'm not telling you anything you don't already know.

The reason this is not proof of superior DOF is simple.  The accepted CoC translates to a smaller radius in the imager and results in a smaller acceptable level of diffraction.  The maximum (smallest) acceptable aperture is therefore reduced.  Nowhere is  this more dramatic than in the P&S's where maximum aperture is often f/8 or less!  This reduction in best aperture precisely offsets the reduction in required magnification.  The whole f-stop issue is nonsense.  When you talk about exposure you use f-stops.  When you talk about DOF you don't.  You cannot claim a DOF improvement due to focal length reduction when it is, in fact, due to an aperture change!

Ray, you obviously understand the difference between aperture and f-stop (which many apparently do not).  I also believe that you understand that you understand the exposure issues surrounding larger versus smaller sensors.  Let's take your 10D plus 1Ds example again only pretend there isn't any such thing as f-stop.  We'll shoot a subject with the 1Ds+50mm using some midrange aperture and a 1/125 shutter.  We then should the same subject with the 10D from the same location using a mythical 31mm lens to provide equivalent FOV.  We use the same aperture but with a faster shutter to compensate for the inherent improvement in sensitivity that results from the gathered light being spead over a smaller area. Which one will have greater DOF?  The 10D will by virtue of the smaller magnification only.  If we maximize DOF by using the smallest acceptable aperture, the DOF of the two will be about the same until high magnifcations where the 1Ds will pull ahead.  The last part of that is non-obvious but true nonetheless.

The DOF advantage myth of small digital formats comes from two sources.  First, people are accustomed to shoot something at f/8 and 1/60 at ISO 100 (for example) regardless of format.  They observe (rightly) that the smaller format has better DOF but fail to realize that f/8 is NOT fixing the physical aperture. The second source is that these smaller sensors don't have lenses that can open up like faster 35mm lenses do, so they never see restricted DOF from these cameras.  Their conclusion is that smaller formats have better DOF accross the board when that is not true at all.

Larger format film shooters also see DOF as limited but for a different reason.  Larger formats are optimized for larger print sizes so the CoC and diffraction tolerance don't scale with the imager size.  MF is not optimized for high magnifications and 8x10 prints.  If it were it would exceed the performance of 35mm in DOF at the cost of resolution.
Logged
Ray
Sr. Member
****
Offline Offline

Posts: 8939


« Reply #36 on: December 05, 2003, 10:28:26 AM »
ReplyReply

Quote
Quote
as far as I can tell, everything you say is true about the optical relationships between focal length, image size formed in the camera (and so indirectly, camera format), aperture diameter, aperture ratio, and subject distance.

Good! I'm glad we've cleared that up  Cheesy

As to whether or not some of my statements are relevant is something one could argue about forever. Relevant to what? Those of us who are creative are not restricted to fixed patterns of behaviour. We like to experiment a bit and try something different now and again. Whilst I personally would not go to the trouble of attempting to use a 300mm lens, designed for the 35mm format for example, on an MF body, I would not criticise someone for trying it. The circular image with a gradual fade-off at the perimeter could be quite interesting.



Quote
The options you describe involve the photographer who is using a smaller format either (a) moving back, in order to use the same lens instead of a shorter focal length lens that would often be smaller and lighter, or ( using a smaller aperture ratio, perhaps in order to use the same shutter speed instead of a using a faster one. Neither seems like the first or second choice in most situations!

That might be your opinion, but for me option (a) is often the first choice. When I do indoor shots with my D60, I often use my el cheapo Canon 50mm F1.8, partly because it's my sharpest lens; partly because I can stand back a few paces and get greater DoF at whatever aperture I choose and partly because, on a D60 the lens become effectively an 80mm lens which is more ideal for portraiture.


Quote
instead, the primary change has always been seeking roughly the same composition (perspective, depth of field, and even degree of diffraction limitation) by moving to a shorter focal length, proportionately lower aperture ratio (same aperture diameter)

Not entirely true. There are a lot of wild life photographers who actually use longer focal length lenses than the MF and LF photographers. Are there any 300-800 zooms available for 10x8 cameras?  Huh


Quote
the most extremely shallow DOF I have seen in film photography usually comes from the smallest mainstream film format, in things like portraits done with ultra-fast 35mm format lenses.

All[/i] photos are usually done with 35mm lenses, fast or slow because it's the most ubiquitous format we have. Although the paradigm is now changing, the number of extant 35mm photos must be staggering.
Logged
Ray
Guest
« Reply #37 on: December 05, 2003, 07:28:03 PM »
ReplyReply

Quote
Quote
  Imagine that you have access to any lens you desire for any format; any focal length, any maximum aperture, etc., with no size, weight or cost worries; and you wish to make a particular photograph with one of several cameras of different format sizes. That is, think only of artistic a) would you desire to use the same subject distance and perspective in each case, or to change both when changing formats?
 would you desire the same depth of field in each format, or to change this when changing formats?considerations for a moment.

It would depend on the subject, the circumstances and how much time I have available. With no time constraints and a large choice of lenses and different format cameras available, ideally I would like to try different lenses with different effective focal lengths, with different aperture settings and different effective DoFs, on different formats, creating different perspectives of the same subject from different angles and creating images of differing resolution for different degrees of print enlargement. (Provided the subject was interesting, of course.)

In circumstances where the subject would not lend itself to such experimentation, I would choose the format, the lens, the f stop and shutter speed I thought most appropriate and would try to balance the various trade-offs in making those choices. For example, if I were shooting in a dimly lit nightclub (or even a not so dimly lit place) and wanted a reasonable DoF and also wanted to remain inconspicuous, I might choose the smallest format camera available. If I were shooting distant wildlife I would almost certainly choose 35mm and the choice of aperture would then depend on such factors as whether or not the lens had Image Stabilisation and at which aperture the lens was sharpest, and whether or not using a tripod was practicable.

If I were shooting a panorama I would choose the largest format camera in my kit, but not if it was windy because it would be difficult to get a sharp shot. I would then make do with MF.

So you see, there are so many variables, a simple answer is not possible.

But I do get the impression you are rather envious of owners of the APS size DSLRs who have this huge choice of 35mm lenses that are effectively upgraded by the cropping factor.  Cheesy
Logged
Ray
Guest
« Reply #38 on: December 06, 2003, 08:25:10 PM »
ReplyReply

Quote
Ray,
   you seem to have completely misunderstood my question, which in particular was NOT about deciding which format to use for a certain situation. .
BJL,
Perhaps I have misunderstood your question, but I suspect it is you who has not understood the implications of your question. Read your own question again.

.... access to any lens for any format .... think only of artistic considerations.

I think perhaps you are trying to elicit from me the straightforward answer along the lines .... if I had carefully composed my picture using a 35mm camera and had chosen 1/250 sec at f8, and then changed my mind and decided to use (or had been asked to use) a 6x9cm MF camera for the same scene, having already done the work from an artistic point of view I would then change the f stop to f16 (or maybe F13.5) and the shutter speed to 1/60th, having selected a lens of equivalent focal length to keep the FoV the same.

Maybe I would. I would certainly have good logical reasons to do this because, as everyone participating in this thread must surely know (and I know that you know that I know) f stop has to be increased for equivalent DoF as one moves up to a larger format.

However, there are lots of reasons why I might not abide by this simple transformation; some of them artistic and some purely logical. Get into the real world, BJL!  Cheesy

For a start, if I can change my mind about which format of camera to use for a particular scene, it's quite probable I would change my mind about some elements of the composition once I have a completely different camera in hand. It might just be due to the effect of squinting with one eye as opposed to looking at an 'upside down' or reversed image with two eyes.

It might be because I know that a particular lens does not have the required performance at a particular aperture, say not sharp in the corners at an equivalent aperture when the corners might in fact be important in that particular composition.

It might be because the different format is not just larger or smaller but of different proportions.

It might be because one camera has a tilt mechanism and the other doesn't.

In general, different formats with different lenses will have different strengths and weaknesses. It would be foolish to ignore these and just perform a simple transpose of F stop and shutter speed.
Logged
Ray
Guest
« Reply #39 on: December 07, 2003, 11:59:10 AM »
ReplyReply

Quote
It is then that you can freely choose to duplicate your photographic choices in another format.  Once you do that, you will see that DOF is not dependent on sensor size.
It's actually quite difficult to accurately duplicate photographic results in another format, especially when moving down in format. There's usually a consequent loss in resolution and tonality.

Show me where I've written that DoF is dependent on sensor size and I'll apologise for getting it wrong.  Cheesy
Logged
Pages: « 1 [2] 3 4 »   Top of Page
Print
Jump to:  

Ad
Ad
Ad