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Author Topic: Why full frame for landscapes at low ISO?  (Read 17200 times)
JeffKohn
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« Reply #60 on: October 28, 2009, 04:14:52 PM »
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Quote from: Chris Pollock
However, a lot of landscape shots will be taken with everything at or close to infinity, so there will be no need to stop down for DOF.
I shoot landscapes and nature almost exclusively, and I practically never focus at infinity. Usually there's some sort of foreground or at least middle ground that needs to be in focus.
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Ben Rubinstein
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« Reply #61 on: October 29, 2009, 01:43:57 PM »
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When I shot landscapes I used a 70-200 more than anything wider, I have only 2 pictures shot with my 17-40L. Now with stitching and urban landscapes I'm using a 100mm lens and f22 isn't enough. I don't care about the calculations or the physics or the tirades, on a crop camera I would have more problems with diffraction as I would still have to stop down.
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BJL
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« Reply #62 on: October 29, 2009, 02:18:05 PM »
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Quote from: pom
I'm using a 100mm lens and f22 isn't enough. I don't care about the calculations or the physics ... on a crop camera I would have more problems with diffraction as I would still have to stop down.
pom, this should be very easy to understand without any fancy calculations: equal f-stop and equal FOV with a smaller format gives more DOF, so when getting enough DOF is the issue, you still have to stop down, but not to as high an f-stop. (If I may risk one calculation, about f/14 on EF-S would give as much DOF over the same FOV as f/22 in 35mm, f/35 in 645 ...)

So please stop comparing diffraction effects at equal, high f-stop: a smaller format never has to be used that way.
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Luis Argerich
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« Reply #63 on: October 29, 2009, 02:22:21 PM »
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Quote from: Chris Pollock
However, a lot of landscape shots will be taken with everything at or close to infinity, so there will be no need to stop down for DOF.

What? I wonder if you ever shot a landscape.

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Chris Pollock
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« Reply #64 on: October 29, 2009, 02:46:50 PM »
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Quote from: luigis
What? I wonder if you ever shot a landscape.
Yes, I have.
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BernardLanguillier
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« Reply #65 on: October 29, 2009, 05:11:53 PM »
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Quote from: pom
When I shot landscapes I used a 70-200 more than anything wider, I have only 2 pictures shot with my 17-40L. Now with stitching and urban landscapes I'm using a 100mm lens and f22 isn't enough. I don't care about the calculations or the physics or the tirades, on a crop camera I would have more problems with diffraction as I would still have to stop down.

Yes, the compromise between DoF and diffraction is better with DX than it is with FX.

Cheers,
Bernard
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A few images online here!
Daniel Browning
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« Reply #66 on: October 29, 2009, 05:59:31 PM »
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Quote from: pom
I don't care about the calculations or the physics or the tirades,

I don't know what "tirades" you're talking about, but you don't need physics or calculations to know that f/14 on DX has the exact same DOF and diffraction as f/22 on FX.

Quote from: pom
on a crop camera I would have more problems with diffraction as I would still have to stop down.

No. You would not still have to stop down, because, again, f/14 on APS-C gives you the exact same DOF as f/22 on FF.

Quote from: BernardLanguillier
Yes, the compromise between DoF and diffraction is better with DX than it is with FX.

You are mistaken. The compromise is the exact same with every format size.
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Ben Rubinstein
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« Reply #67 on: October 30, 2009, 02:51:10 AM »
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Anyone like to prove that you get more DOF with crop for a given FOV to the extent of a stop and a half? Or that for a given DOF the diffraction will always be the same?
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Herkko
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« Reply #68 on: October 30, 2009, 11:38:13 AM »
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Quote from: HSakols
Do larger sized prints (eg 16x20) show a significant  improvement just by using a full frame sensor.

For me the answer is yes, but your mileage may wary. Basicly, crop camera is a subset of a full frame. It usually offers you tighter pixels, faster operations and less expensive price. But if we are talking about image quality in general: yes, bigger sensor area with practically same quality of lenses and technology you will naturally get better image quality.

An exaggregated example of image caption area impact: If I'm looking www.shorpy.com I can usually spot 4x5 scans from 35mm even from 400pix thumbnails. More accurate colors, more accurate details, better everything.
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Daniel Browning
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« Reply #69 on: October 30, 2009, 12:57:25 PM »
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Quote from: pom
Anyone like to prove that you get more DOF with crop for a given FOV to the extent of a stop and a half? Or that for a given DOF the diffraction will always be the same?

A visual demonstration requires two cameras with different format sizes and different focal lengths, but the same sensor MTF (total number of pixels), the same OLPF MTF, and the same lens MTF (relative to L/PH, not lp/mm) at the f-number scaled by crop factor. Furthermore, when the MTF of each lens is plotted over defocussing in image space at a given spatial frequency (relative to picture height) at the scaled f-number, the curve must be the same for both.

Personally, I don't have any two camera/lens systems that meet those specifications. All the lenses that I own have sufficiently different OLPF and aberrations that it can skew the DOF results. If there is someone with a D300, D3, 400mm f/2.8, and 600mm f/4, my guess is they would meet the qualifications.

Fortunately, there are experts that have already measured all that stuff. They created DOF calculators. That way people like you and I can calculate DOF without getting results that are skewed by lens aberrations.

But since you do not believe in DOF calculators, there is nothing I, personally, can do to prove it to you.
« Last Edit: October 30, 2009, 01:01:09 PM by Daniel Browning » Logged

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BJL
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« Reply #70 on: October 30, 2009, 01:15:44 PM »
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Quote from: pom
Anyone like to prove that you get more DOF with crop for a given FOV to the extent of a stop and a half? Or that for a given DOF the diffraction will always be the same?
With the slight correction that the DOF change is a factor 1.5x or 1.6x, only slightly over one stop, both are easily proven. But to do so online require using physics and some calculations, which you seem to disdain.

So either do some simple experiments (using crops on the same camera with a 1.6x change in if you wish), or read some basic optical text books.
For DOF, the experiment could be as simple as:
200mm, f/22 vs 125mm, f/14, same lens; crop to same FOV; compare equal sized prints.

But to recap some elementary and uncontroversial optical facts:
1. reducing focal length by factor 1.6 (to fit the desired FOV onto a 1.6x smaller sensor, say) with equal f-stop reduces the circle of confusion size (disc into which a point is blurred by OOF effects) by a factor of 1.6 squared (square of focal length: see any DOF formula).
2. It also reduces image size by the same factor, so enlarging to equal size enlarges the circle of confusion size on the print at each point to 1/1.6 as big as with the longer focal length: "1.6 times more DOF."
3. reducing f-stop by the same factor of 1.6 increases CoC size by factor 1.6 (standard DOF formulas again), and thus in combination with the above, it gives equal sized CoC on equal sized prints: equal DOF and OOF effects when focal length and f-stop are adjusted in the same proportion.
4. The diffraction spot size is determined only by f-stop and varies inversely with f-stop, and so in step 3, it becomes 1.6 times smaller at the focal plane when the f-stop is reduced with the shorter focal length. With the extra factor of 1.6 in enlargement to get an equal sized print, one gets equal sized diffraction spots everywhere.

Conclusion: adjusting focal length, aperture ratio and degree of enlargement in the same proportion given an equal sized final displayed image with equal sized circles of confusion at each point and equal sized diffraction spots: the same DOF/OOF/diffraction trade-offs.
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