spreadsheet showing why M8 and FF have same DOF

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ferider said:
Read the above pdf file carefully, Ted.

Your spread-sheet explains why you could use Leica lens DOF marks also for the M8 (conservative CoC size), but it does not say that M8 and M9 have the same DOF with the same lens and focus distance.

In fact, lens DOF marks mean different things on M8 and FF.

I suggest to drop the subject.
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Seconded. The same lens, on different formats, for a given final print size, will NEVER give the same d-o-f.

Cheers,

R.
 
I read the PDF, great reading. The second part of your sentence contradicts the first part that agrees with my testing. I recommend you get away from the computer sometime, take some photos with an M8 and M9, then go to Costco and make some prints and take a look at them, and then talk about DOF.

Roger - please go back to writing some Amphoto books. I promise to check them out when they arrive at the library.

Thanks.


ferider said:
Originally Posted by ferider
Read the above pdf file carefully, Ted.

Your spread-sheet explains why you could use Leica lens DOF marks also for the M8 (conservative CoC size), but it does not say that M8 and M9 have the same DOF with the same lens and focus distance.

In fact, lens DOF marks mean different things on M8 and FF.

I suggest to drop the subject.
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the zeiss pdf clearly states that the geometric model of detrming DOF is imprecise and gives reasons why.
If you use only the geometric model, all other things being equal when reducing sensor size, then dof will decrease.
BUT all other things can never be equal when comparing from an MP to an M8. The system for arriving at a print size for comparison will be different, The resolving power of the sensor will be different. The dynamic range of the sensor will be different from film. These things all affect the MTF and the zeiss PDF makes it clear that you can not ignore these things. The problem is we don't know how much they affect dof. Therefore no one here can say with any surity that dof will remain the same, increase or decrease.
What is given as surity is the geometric model. That is not good enough. What is given as surity for zero change in dof field is not good enough.
 
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From page nine of the Zeiss document so kindly provided:

4. Smaller film format with the same lens

If we remove a lens from an old analogue camera and attach it to a digital camera of the same system that has a somewhat smaller APS-C sensor, then there is a "crop factor". We do not talk about an extension of the focal length, it doesn’t exist in this case. After all, the lens does not know how much of its image circle we are capturing with our sensor.
The size of the object field is reduced by the crop factor while the object-side light cones remain the same, as long as we use the same lens and do not change the aperture setting.

That is why the points of the light cones may not be located so far from the focal plane if we want to maintain the same ratio of diagonal to circle of confusion. Reducing the size of the film format therefore reduces the depth of field by the crop factor.
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tlitody said:
But that is only the geometric model which the document then goes onto explain is not good enough.

Read it all carefully
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I read it carefully. There is nothing new. Optical systems are complex. And it explains it very well.

But that is not the discussion. The OP believes that format has no impact on DoF when using a specific lens. The point on page nine is a simple relationship to show that assumption is wrong. Since we have no specific lens or condition, the relationship is a valid guide. And in that case, it is "good enough."
 
cool

cool

So, a couple of facts, especially for the non-M8 owners "bench talking" here... The M8 sensor (27 x 18mm) is quite larger than APS-C, typically about 22.3 x 14.9mm for Canon, and is closer to APS-H which is 28.7 x 19.1mm (used by Canon in CCD and CMOS 1D models.

For the two sizes above, Canon's own DOF calculator uses .019 CoC for their APS-C, and .023 for their APS-H, .030 for their FF. So do we RFF'ers really think that we're seeing different CoC values than Canon users? I mean I realize we're special, we use Leica's, but really, eyesight differences??

Have I ever told you about the story of how I get eye checkups? I go to two or more doctors in the same morning or afternoon, come away with 2 or more different prescriptions, talk them over with a doctor I trust, and then get my prescription. Sometimes I will get prescriptions for both or all exams, especially since I've found 39dollarglasses.com deals.

Anyhow, back to the topic, so let's cut out the CoC and DOF mumbo jumbo and go back to why you and some others think that for an M8 to equal an MP's hyperfocal distance with the same lens, that you need to move the barrel marker wider 1 stop on the M8? I've heard about square roots of 2, read all links referred to, and even with the zeiss link of the day, it does not in any way say that a sensor sized between APS-H and FF (32.44 diag. to be exact for the M8) needs this 1 stop, or 1.4 stop barrel movement for hyperfocal distance.

BTW, you can infer Canon's z-constant from it's calculator, which is 1410 to 1480, the same I get for the M8's with Leica's provided CoC.

So let's see some quantitative numbers from you folks who think Leica is wrong. As Clara Peller would say to you - where's the beef?? :D

http://www.youtube.com/watch?v=Ug75diEyiA0

Finder said:
From page nine of the Zeiss document so kindly provided:
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ampguy said:
So, a couple of facts, especially for the non-M8 owners "bench talking" here... The M8 sensor (27 x 18mm) is quite larger than APS-C, typically about 22.3 x 14.9mm for Canon, and is closer to APS-H which is 28.7 x 19.1mm (used by Canon in CCD and CMOS 1D models.

For the two sizes above, Canon's own DOF calculator uses .019 CoC for their APS-C, and .023 for their APS-H, .030 for their FF. So do we RFF'ers really think that we're seeing different CoC values than Canon users? I mean I realize we're special, we use Leica's, but really, eyesight differences??

Have I ever told you about the story of how I get eye checkups? I go to two or more doctors in the same morning or afternoon, come away with 2 or more different prescriptions, talk them over with a doctor I trust, and then get my prescription. Sometimes I will get prescriptions for both or all exams, especially since I've found 39dollarglasses.com deals.

Anyhow, back to the topic, so let's cut out the CoC and DOF mumbo jumbo and go back to why you and some others think that for an M8 to equal an MP's hyperfocal distance with the same lens, that you need to move the barrel marker wider 1 stop on the M8? I've heard about square roots of 2, read all links referred to, and even with the zeiss link of the day, it does not in any way say that a sensor sized between APS-H and FF (32.44 diag. to be exact for the M8) needs this 1 stop, or 1.4 stop barrel movement for hyperfocal distance.

BTW, you can infer Canon's z-constant from it's calculator, which is 1410 to 1480, the same I get for the M8's with Leica's provided CoC.

So let's see some quantitative numbers from you folks who think Leica is wrong. As Clara Peller would say to you - where's the beef?? :D

http://www.youtube.com/watch?v=Ug75diEyiA0
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We did all this. You yourself provided photographic evidence that the science actually describes what we have been saying all along. I suggest you take that fine Zeiss document and read it carefully.

I don't think there is anything left to say on this topic.
 
This makes me happy I'm down to two fixed lens film cameras and a Hassy that I have no intention of getting another lens for. DOF calculations are pretty easy w/ these. Just stop 'em down for landscapes and open 'em up for portraits.
 
ampguy said:
My test results are here:

http://matsumura.smugmug.com/Journalism/M8-and-M6-depth-of-field/12529753_UJFd5#898702880_f85d9

Over 30,000 views, no one can see any difference between the M6 film and M8 DOF, except for Finder, and I've talked with dozens of folks who've magnified 10-400x to examine.

Amazing how Finder and others can ramble on these threads for days, yet when it comes to taking real photos and printing, they're too lazy to do it.
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And I did shoot and post examples. I even gave you plots to to show quantitative data. And your example photos clearly show a change in DoF.

So unless you got something more than insults and snide comments, I think this is a really pointless conversation.
 
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