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04-26-2013, 11:38 AM   #16
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QuoteOriginally posted by 2351HD Quote
Hi all,

This is my first post here as I am considering a 645D system and have a few questions.

When comparing to 35mm Full Frame, how much further do you have to stop down the lenses to get a similar deep depth of field on the 645D as I would at say F8 on 35mm FF? Meaning, to get the same DOF for the same field of view, if the 35mm is at f/8, would the 645D have to be at f/11, or f/13, or f/16?

Can the 645 lenses handle being stopped down more without suffering from diffraction softening the images? I know on my Leica M9, anything beyond say f/8 with a 21mm Super Elmar will start to reduce contrast and overall sharpness.

Also, of those who are using the 645D, how do you find the LCD for checking critical sharpness across the image? Is it accurate enough?

Finally, I shoot many seascapes and waterfalls etc and using ND filters can often put my exposure longer than 60 seconds. It is this reason alone that I am considering not getting the new Leica M as it is restricted to 60 seconds max exposure at base ISO. How is the 645D at exposure times longer than 30 seconds, say at 60, 90 and 120 seconds? Are the files still clean and free of banding etc?

Any help would be greatly appreciated. My new Leica M is on backorder and I have about 2 weeks to decide to ditch the M system, keep my NEX and go with a MF or SLR system.

Thanks, Scott

Equivalent DOF: a little less than one stop (multiply the F-stop number from 36x24 by 1.3).

Diffraction: Not a problem; in fact there's an advantage. Diffraction scales with aperture. If you set the equivalent DOF with the equivalent FOV you'll lose a bit due to diffraction, but you'll gain ~30% resolution overall because the magnification to the eventual print will be much less.

04-26-2013, 07:57 PM   #17
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QuoteOriginally posted by ElJamoquio Quote
The equation is still good, it's just that your criteria for evaluating the image has changed. Viewing an image at 100% is much higher standard (about 10 pixels per CoC if I recall correctly from the last time I did the equation) than a human's ability to resolve lines in a 'real' image.
Nope, if anything, it's a lower standard. I had drum scans made of the transparencies at 5400dpi (equivalent to 100 megapixels) and looked at those 100%. So, no, I'm speaking from actual experience and results. Digital changes everything.
04-28-2013, 11:55 AM   #18
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QuoteOriginally posted by ElJamoquio Quote
The equation is still good, it's just that your criteria for evaluating the image has changed. Viewing an image at 100% is much higher standard (about 10 pixels per CoC if I recall correctly from the last time I did the equation) than a human's ability to resolve lines in a 'real' image.
It doesn't matter how you view it. Pick 33% or 50% if you'd like The bottom line remains and can easilty be seen: The more you pixels you pack in (the smaller the pixel pitch), the less perceived depth of field, as long as you are using all of the pixels and not downsampling.
04-28-2013, 12:09 PM   #19
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QuoteOriginally posted by chicagonature Quote
Nope, if anything, it's a lower standard. I had drum scans made of the transparencies at 5400dpi (equivalent to 100 megapixels) and looked at those 100%. So, no, I'm speaking from actual experience and results. Digital changes everything.
QuoteOriginally posted by chicagonature Quote
It doesn't matter how you view it. Pick 33% or 50% if you'd like The bottom line remains and can easilty be seen: The more you pixels you pack in (the smaller the pixel pitch), the less perceived depth of field, as long as you are using all of the pixels and not downsampling.
I'm seeing double!





I don't think that a 'pixel' level DOF is relevant to today's photography. There's enough pixels that it all blends together, so in reality you're always downsampling anyway, unless you're talking about viewing a large picture up close.

04-28-2013, 12:11 PM   #20
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QuoteOriginally posted by ElJamoquio Quote
Equivalent DOF: a little less than one stop (multiply the F-stop number from 36x24 by 1.3).

That's only true for moving from one film format to another, not film to digital. And that's my entire point. I did the "diagonal conversion" of 1.6 (medium format film of 41.5x56mm to 24x36mm) thinking that would work, but it didn't (as my original post explains). I went from FILM medium format to 35mm DIGITAL. Just factoring in the diagonal (crop factor, you might say) is not the only factor. Pixel pitch matters. How much exactly, I say 3 x pixel pitch, which works for very small apertures. It may be 2 x pixel pitch for the "sharper" apertures like f/5.6 and f/8.

Please do physical tests and find out for yourself. You'll be as surprised as I was. You can test it without a 645D, though.
04-28-2013, 12:58 PM   #21
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QuoteOriginally posted by chicagonature Quote
That's only true for moving from one film format to another, not film to digital. And that's my entire point.
I wasn't responding to you. I recognized your point. I'm still having trouble reconciling the huge discrepancy you bring up with any other datapoint, but again, I wasn't directly refuting you with the post you're quoting. I was quoting the OP. I quoted the light-theory-based numbers.

I could believe that there's some sort of pixel-lens or telecentricity requirement for digital that isn't there for film.
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