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Author Topic: New Leica Digicam  (Read 16024 times)
victoraberdeen
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« on: December 04, 2003, 01:44:48 AM »
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Yes, hard to follow!

However DoF is not changed by the size of image sensor. I think the reference to larger f-stop is about the amount of light falling on the sensor?
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BJL
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« Reply #1 on: December 04, 2003, 12:02:23 PM »
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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.
Exactly Craig; thank you for the concise statement.
   In practice, smaller format digital cameras so far have more DOF even wide open because their maximum apertures are smaller, despite often having somewhat lower (faster) aperture ratios. With film formats, this is usually not true: maximum apertures on lenses of similar FOV are rather similar all the way from "large large format" (8"x10") down to 35mm.
   So the question is whether this trend can continue further. To match the aperture of f/2.8 in 35mm format requires about f/2 for APS formats, f/1.4 for 4/3" format, f/0.7 for 2/3" format. Given that some digicam zoom lenses already reach f/1.8 wide, or f/2.4 tele, getting a zoom down to f/1.4 at least seems quite realistic when you remember that the aperture and front element size is not getting any bigger. f/0.7 though Huh
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Craig Jones
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« Reply #2 on: December 05, 2003, 09:03:35 AM »
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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).
Yes, exactly!
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BJL
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« Reply #3 on: December 05, 2003, 01:33:35 PM »
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Ray,

    perhaps the closest we will come to agreement is that, in your somewhat unfortunate situation of using a camera (D60) with a sensor of one size in conjunction with lenses originally designed for a larger sized format, you are often constrained to either use a lens of longer than ideal focal length, and hence forced to back off in order to fit the image, or to use a slow, wide angle lens. Blame lens limitations, not the format!

    I really want to remove issues of current, quite likely temporary, limitations in lenses available for newer smaller formats from claims about inherent advantages or disadvantages of one format over another, so can I ask you some questions?
   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 considerations for a moment.
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?
   Moving back towards reality by bringing size and weight limits into the picture only adds more flexibility for smaller formats, which fairly consistently achieve the same maximum aperture diameter in the shorter needed focal length with a somewhat smaller (and cheaper?) lens.
   That brings me to your second point about long, fast lenses for wildlife photography and such. I am not sure how relevant it is to the topic at hand, but you are quite right in pointing out that it is harder to do that sort of photography in larger formats, which relates to the relative lack of such lenses for MF and LF. This is because of one of the true inherent differences between formats: larger formats generally require longer exposure times and longer lenses, and both of these make them less suited to extreme telephoto work.
   But this is straying very far from the original DoF discussion.

   About my shallow DOF portait example, it is more thanteh perdominance of 35mm. After all, for professional portraits, MF is a rather big player. And yet work out what would be required to match the shallow DOF of a 35mm format 85/1.4 with its 61mm maximum aperture. The only medium format lenses that can match that aperture are 180/2.8 and longer, so the narrower FOV requires backing off and gives more DoF; nothing in LF can do better either. The same happens with a 135/2, and for more or less any fast 35mm lens: there is no lens in existence for larger formats that will give you lower minimum DoF for the same subject framing.

   So both basic optical theory and and the practicalities of lenses available for established formats contradict the idea that larger formats have increased shallow DoF potential.

P. S. Probably a 300mm lens for 35mm format could be used on a MF or even 4x5 camera with no vignetting if you avoid the lens hood; telephoto lenses tend to have a natural angular field of view similar to a normal lens (about 50 degrees) and hence vastly excessive image circles, which are then cropped in the camera. (This is the refutation of the common criticism that smaller formats involve more cropping: telephoto lenses for any format with a given telephoto field of view are usually cropping about the same fraction out of a roughly 50 degree FOV.)
   One way to see this is to look at specifications for large format lenses, which often give their angular field of view to let users know which formats and movements they can handle. Wide and super wide lenses offer large angles, but as the focal lengths move up well into telephoto territory, the angular FOV rarely or never drops below 50.
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Ray
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« Reply #4 on: December 07, 2003, 01:16:32 AM »
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Ray,

   why do I get the feeling that you do not want to answer the question that you know I am asking, and keep instead reinterpreting it?
JBL,
Probably because I'm a practical person who is after the best results with the equipment I have and because in practice I simply would not merely transpose f stop and shutter speed with a different format camera in the manner you are suggesting.

Lack of sufficient DoF is a common constraint in photography as you well know. It would be great if one could use f32 with one's 35mm camera and get similar resolution to f8 as well as using the same shutter speed.

What you are doing is setting up a hypothetical situation and asking how I would respond without regard to restraints when the artistic concept itself, right from the beginning, would have restraints built in.

Let me give you a concrete example from recent experience. Many art galleries, museums, historic homes etc have rules about photography. Sometimes no photography at all is permitted. Sometimes photography is permitted but no flash or tripod allowed.

In such circumstances one struggles with the competing constraints of shutter speed and DoF. One usually ends up with a compromise, or no shots at all; perhaps f5.6 at 1/30th is the best one can do.

Enter a nice gentleman like yourself who hands me a Leica Digicam; do I now use F2 at 1/250th? Almost certainly not. I might well stick with the same f stop and shutter speed, thus lifting those constraints, achieving greater DoF and a more appropriate shutter speed for a hand held shot with the shorter lens.

Why are you trying to get me to give you an 'unreal' answer?
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victoraberdeen
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« Reply #5 on: December 07, 2003, 04:12:14 PM »
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DoF is dependent on sensor size

No Ray you didn't make that mistake

However, there are other differences between the lenses produced for different formats that have more serious effects. There are two distances that matter here, subject to nodal point and nodal point to image plane. It is the latter that changes with large format cameras and is the reason you are all failing to understand this topic.

With DSLR's it is only a crop the same crop on a full frame image will be exactly the same.

Sharpness is a compromise...
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victoraberdeen
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« Reply #6 on: December 09, 2003, 11:58:04 PM »
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Ray, No assumption, the focal length needs to be the same. However to retain the subject retain the same percentage size in the image, you would have to assume the leica has the right focal length!

And rude, never
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BJL
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« Reply #7 on: December 10, 2003, 09:50:41 AM »
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... 2/3rds a silly term really - for them that still use inches
2/3", 4/3" are stage anachronisms, and I find 1/1.8" even weirder (why not 5/9?), but here is the trivia question for the day:

To what important photographic dimension does "35mm" refer to?
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BJL
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« Reply #8 on: December 12, 2003, 08:16:20 AM »
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Wierder to me is that the focal length scale on the lens is in "35mm equivalents" rather than real focal lengths. So far those equivalents have been hidden in electronic dispays. (Apart from purism, I disagree with the standard choice of conversion factor, since it assumes comparing to 35mm format by cropping to 35mm frame shape and so using full frame width but discarding some height; I am more likely to use the full frame height, possibly discarding some width from either shape when cropping for shapes like 10x8" or US letter.)

   On the other hand (or other side), I like the idea of having the LCD as big as it can possibly be, filling the entire height of the back panel.


   Nice to be talking abut the original subject of this thread at last, on page 8!
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mbridgers
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« Reply #9 on: December 01, 2003, 08:14:44 AM »
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DP Review is reporting the announcement of the new Leica Digilux 2.  

Digilux 2

Hope it's fast!
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Ray
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« Reply #10 on: December 04, 2003, 05:30:42 AM »
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Yes, hard to follow!

However DoF is not changed by the size of image sensor. I think the reference to larger f-stop is about the amount of light falling on the sensor?
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However DoF is not changed by the size of image sensor.

I've got a sense of deja vu here. If the only change is the size of the sensor, then it's true that DoF does not change, just as merely cropping an image does not change DoF and just as fitting a 35mm back to an LF camera does not change DoF.

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.



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I think the reference to larger f-stop is about the amount of light falling on the sensor?

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.

With my D60, the noise at ISO 400 is not significantly less than the noise one gets underexposing the shot by using ISO 100 and the same shutter speed.
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pmkierst
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« Reply #11 on: December 04, 2003, 11:04:59 AM »
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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!
Um yeah, true. What is your point?

I don't get why people argue this over and over and over again. Skip all the math, skip all the theorizing. Try this:

Take a small sensor camera. Make it a P&S, a 35mm, what ever. Select a 3D scene. Select an exposure; lets say 1/250 @ F8 @ ISO 100. Take picture.

Now take a 4x5. Insert ISO 100 Film (or a digital back if you are quite well off). Select focal length for the same composition from the same position. Select the same exposure. Do not use movements. Take picture.

Print both at the same size; lets say 8x10. Visuallly inspect. Do they have the same DoF? I can assure you it is not even in the same ballpark. The DoF in the 4x5 will be very very very thin. The P&S DoF will be very good.

Now argue all you want on why, but it still holds in the real world: DoF EFFECTIVELY depends on the sensor size. You can blame it on focal length if you want, you can point at this variable or that changed, argue to you are blue in the face, but you will still have more DoF for your desired composition on the small sensor camera.
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Paul K.
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« Reply #12 on: December 05, 2003, 09:50:22 AM »
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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.

I don't think you give other people enough credit. Some people -- like me -- have a different basis for evaluation. I am well aware of the "truth", but prefer to look at things more realistically. So I take issue with your argument not because it is wrong (it isn't), but because it is a distraction from the real outcome. Those people don't necessarily fail to realize that the physical aperture has changed, but perhaps they like shooting at 1/60. What the technical version of the argument fails to account for is the real world. Indeed -- in the real world -- it can be very difficult to limit DoF sufficiently with small sensor cameras. Incidently, it is quite easy to achieve very limited DoF with large format, but rarely desirable for two reasons: 1) LF shooters are extremely shallow DoF types of people for the most part and 2) LF lenses suck wide open. This is because they are simple, light and there is little motivation to change this because of (1)

35mm is the only format where people happily strap on very large heavy lenses to with the resultant shallow DoF. For the most part, equivilants to these lenses are not available in other formats. All participants here know this, but choose to argue the technical aspects rather then the outcome: In the real world, a small sensor camera will have difficultly restricting DoF. Maybe they will release a F/0.7 lens on a small-format camera in the future with ISO 16 so you can both limit DoF and have a slower shutter speed, but I have my doubts.

Incidently, Macro lenses are certainly available for both MF and LF. However, the extremely small F/stops required to get sufficient DoF make for very long exposures (or massive strobes) and make them more then a little inconvient to use. Outside of the studio, even the slightest breeze will destroy your shot. Just one part of the reason why you don't see them used much.
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Paul K.
Ray
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« Reply #13 on: December 05, 2003, 11:24:04 AM »
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I noticed you didn't refute anything I said.  

Yes I did. You tried to say that F stop and DoF considerations do not apply across formats. When I challenged you on this point, you then wrote that it only applied to exposures and it was nuts to pretend that a constant DoF across formats was relevant because people do not take photos of bits and pieces but whole compositions (or words to that effect).

What is nuts or irrelevant, or what constitutes a bit or a piece or a whole composition, is a matter of opinion; a matter of taste and a matter of esthetics. I'm trying to cut through your obfuscation with some facts.

That a 300mm lens at a given f stop will have the same size aperture and the same DoF (from the same shooting position)[/I]irrespective of the format the lens was designed for is surely of some academic interest to those who didn't already know it, and is surely of more than academic interest to owners of APS format DSLRs who didn't already know it.


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The resultant improvement in DOF in this test is not due to the change in sensor size,

You seem to be looking for direct causes. Are you trying to say that only direct causes are valid? A lot of things that happen are a consequence of a consequence of a consequence etc. Exponents of Chaos Theory will have us believe that a butterfly flapping its wings in South America might just tip the balance and cause a storm in Australia (I wish it would. It's still pretty dry over here.) This is an extreme example and I don't take it seriously. That reducing sensor size might (and certainly will if you keep the f stop and FoV the same) result in an increase in DoF has a much more direct causality.

By the way, it's difficult to hide a phrase like "same f stop" in such a short sentence. I don't know how I managed that.
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BJL
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« Reply #14 on: December 06, 2003, 10:46:28 PM »
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Ray,

   why do I get the feeling that you do not want to answer the question that you know I am asking, and keep instead reinterpreting it? Surely I have made it clear that I am not talking about constraints of lens availability (like tilt or no, better quality for one format than the other), or issues of frame shape (it is possible to crop, even though I know you prefer not to!), and I am certainly not talking about changing your mind about your artistic intent; I am talking about how you would go about achieving the SAME artistic intent, including framing after cropping if necessary, with cameras giving a different image size.
   And I think that buried in your reply, you have agreed that, at least with the added assumption of same aspect ratio, you would indeed pursue a given intent by maintaining about the same subject distance and aperture diameter, and so different f-stop.

   Since my original objection was to the accusations against smaller formats of constraining one to less shallow DOF options by arguing on the often tacit assumption that aperture ratio would be, should be, or usually is keep the same with different formats, I am now satisfied with such agreement as we have achieved.
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Ray
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« Reply #15 on: December 07, 2003, 07:42:15 PM »
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DoF is dependent on sensor size

No Ray you didn't make that mistake
Victor,
Well. thank you for that small mercy. I think perhaps it is really you who is responsible for this constant flow of diarrhea from Craig, aided and abetted by BJL  

I'll refer you to my first response to you on page 1 of this thread. You seem to be suffering from a memory lapse.

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I've got a sense of deja vu here. If the only change is the size of the sensor, then it's true that DoF does not change, just as merely cropping an image does not change DoF and just as fitting a 35mm back to an LF camera does not change DoF.

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 there anything in the above two paragraphs that is (a) incorrect, or ( indicates that I don't understand the difference between cropping an image and changing the focal length of the lens. I think not.  

What I really don't understand about this topic is how anyone can misinterpret such plain, factual and clearly expressed statements. That's a real mystery.  Cheesy
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Ray
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« Reply #16 on: December 09, 2003, 09:13:19 PM »
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You can get the photo with any camera, Leica, Rollieflex, MPP exposing a 30th at f5.6 and get a publishable photograph, if the focal length of the lens is the same you’ll even have approximately the same depth of field. The light making the image is the same regardless of image size. Ergonomics is another story!
There is an implicit assumption in this example that the maximum focal length of the Leica digicam is less than the focal length of whatever lens was being used at F5.6 on the 35mm camera.

I don't wish to be rude, but I sometimes get the impression that you are failing to see the woods for the trees. But then you probably feel the same way about me  Smiley .
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victoraberdeen
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« Reply #17 on: December 10, 2003, 10:28:56 AM »
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What is measured is simple enough, but never used becaue we all use the Length x depth. But worse it is in inches why not mm!
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flash
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« Reply #18 on: December 11, 2003, 11:52:59 PM »
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Some of my Canon lenses have a mask inside the lens to help reduce flare. Looks similar to this.

Gordon
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Bobtrips
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« Reply #19 on: December 01, 2003, 10:09:48 AM »
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(To be read with an aristocratic demeanor...)

It is a Leica!

It has proper controls, not those absurd menus and buttons!

It has an EVF?Huh??

(Let the rationalization tap dance begin....    )
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