Depth of field on M8 vs MP... Sorry for being thick!

Sebben said:
Yes it is magnified. But that doesn’t mean that there is less in focus. :bang:
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It isn't about focus. Only the object plane is "in focus."

This is about sharpness--a subjective quality based on the human visual response. Making an image bigger or small changes sharpness. Didn't you see my plots?
 
Hi all, kudos to Finder and Ferider for actually showing something. Ironically, this project may pre-empt or delay my viewing of "It's Complicated" which I've anxiously been waiting for and finally got today at the local redbox ;)

Here's what I've taken so far, and expect to have the film scans tomorrow:

Both on tripod, both 1/30th, f8, same 35 lux pre asph lens. M8 is at ISO 640 (selected to match expired Portra 800), all settings STD, auto WB. M6 with Portra 800, (film is expired, but was refrigerated), manual exposure.

Focus point 1 is exactly on focus on "Scotch" tape dispenser about 6 feet away on scale where r hand of "3" meter mark is just at the f8 line on DOF scale

Focus point 2 is with focus moved to about 7 ft where the r of the "3" meter mark is now just at the f5.6 line.

Some contrasty remotes, and blankets were strewn around at distances from about 3-10 feet.

My hypothesis is that the DOF will be the same in 4x6, and 8x10 prints. But I will also make prints of both the film scan at focus point 2 where some think the stop needs to be on an M8 to approximate DOF of a ff film image with same lens at same distance, and the M8 file at focus point 2, to see if moving the M8 one stop wider is needed for equivalent DOF.

Any questions on this methodology? I still have 30 frames on the film roll, but expect to process the roll tomorrow sometime.

Thanks, have a great weekend everyone.
 
ampguy said:
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My hypothesis is that the DOF will be the same in 4x6, and 8x10 prints. Bu

.
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That one is so wrong that you don't even need to test it. The essential of DOF is that your eye cannot distingiush the size of the blur circle due to lack of resolution. And you are enlarging them....
 
:confused:What has resolution of the sensor got to do with it??? The native COC of the sensor is 6.8 micron, so you are well over a meter wide at a guess then.
 
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Finder said:
Why cloud the issue with facts...
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Ha ... you finally got it!

Physics, perception, reason and the interweb ... what could possibly go wrong ;)

PS got to admire your tenacity, given you answered it in the first few posts
 
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jaapv said:
:confused:What has resolution of the sensor got to do with it??? The native COC of the sensor is 6.8 micron, so you are well over a meter wide at a guess then.
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I rather thought your statement "The essential of DOF is that your eye cannot distingiush the size of the blur circle due to lack of resolution." was implying that resolution had everything to do with it.
 
Yes - the resolution of your eye at the viewing distance. As soon as you cannot see the difference between an out-of-focus image point and a sharp image point due to your eye not being able to resolve it, your brain perceives both points as being equally sharp. That is the essential of DOF.
 
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jaapv said:
Yes - the resolution of your eye at the viewing distance. As soon as you cannot see the difference between an out-of-focus image point and a sharp image point due to your eye not being able to resolve it, your brain perceives both points as being equally sharp. That is the essential of DOF.
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So we need to base our calcultions on suiting the resolution of the eye. And to do that we need to create C0C of a certain size which gives us sufficient resolution on the print. So Resolution is actually fundamental to this DOF thing working.

Now that we have established that, just for fun lets take a sensor which is the same size as the M8 sensor but increase the number of pixels it can produce by a factor of 1.33 linearly or whatever the sensor crop factor was. Now we take our picture and print it to the same size as before. The question is have we enlarged it as much as when we had less pixels? Relative to the sensor size we have but we have not spread the pixels so much.

Have a little think about what that means with regard to the theory that DOF is realtive to sensor size.
 
tlitody said:
Now that we have established that, just for fun lets take a sensor which is the same size as the M8 sensor but increase the number of pixels it can produce by a factor of 1.33 linearly or whatever the sensor crop factor was. Now we take our picture and print it to the same size as before. The question is have we enlarged it as much as when we had less pixels? Relative to the sensor size we have but we have not spread the pixels so much.

Have a little think about what that means with regard to the theory that DOF is realtive to sensor size.
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Actual DoF will not change. Your above example is the same as using finer grained film.
 
Roland

Roland

No difference here either with 4 individuals, and 3 different monitors.

Not saying it's not there, just that we don't see it.

Just my opinion, but I don't think photoshop reducing a film image is equal to taking a photo (with it's already pre-captured sharpness attributes) with an actual M8 and lens, also, how are you emulating the movement of the focus ring one stop more than film, as you are recommending to the OP?

ferider said:
Look at the background and the size of the oof "blur" circles (behind her left ear).
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Jappv

Jappv

Let's not make premature assumptions, until we have the actual physical data in hand.

jaapv said:
That one is so wrong that you don't even need to test it. The essential of DOF is that your eye cannot distingiush the size of the blur circle due to lack of resolution. And you are enlarging them....
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Finder said:
Roland, nicely put, but I am getting the feeling of Deja vu all over again.
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Huh? Roland cited the same two sources as I...Luminous Landscape and the Leica forum...and you blasted me for each. And, like Roland, I recommended compensating by one stop on the DOF scale. And you blasted me for that too.

Maybe I should change my name to Roland.

Jeff
 
Jaques

Jaques

If you are sincere, and want to know about diffraction, let me know, and I'll summarize the issues in a different thread.

Jaques H said:
I totally don't understand this.:confused:

Yes, 1/1000 as fastest shutter speed is too slow for our finer grained films, digital sensors, with apertures above f4 or 5.6 or so.


1K = 1/1000 ? I thought that was a fast shutter speed not slow.:confused:
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ampguy said:
If you are sincere, and want to know about diffraction, let me know, and I'll summarize the issues in a different thread.
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Totally Ampguy.
If I am going to get diffraction problems with my digital cameras at stops greater (or smaller?) than f4, I want to know about it!
 
tlitody said:
So we need to base our calcultions on suiting the resolution of the eye. And to do that we need to create C0C of a certain size which gives us sufficient resolution on the print. So Resolution is actually fundamental to this DOF thing working.

Now that we have established that, just for fun lets take a sensor which is the same size as the M8 sensor but increase the number of pixels it can produce by a factor of 1.33 linearly or whatever the sensor crop factor was. Now we take our picture and print it to the same size as before. The question is have we enlarged it as much as when we had less pixels? Relative to the sensor size we have but we have not spread the pixels so much.

Have a little think about what that means with regard to the theory that DOF is realtive to sensor size.
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sorry - I fail to distill any meaning from this post. Could you please reformulate.
 
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