Crop question....

[Analogicus]

Hello everyone!

I was wondering....
Lets say I have a Leica M8 with a 35mm lens and I take a photo of a given scene at the resulting 46mm FOV. Then I take an M9 - identical sensor, but larger - and take the photo of the same scene, from the same place, with the same lens, and of course at 35mm FOV.
OK.

Now I decide that 46mm works much better for the scene, and I crop the 35mm M9 photo to correspond in framing to the 46mm FOV shot of the M8.

I would think that (lets assume equal lighting, exposure, DR, etc) my two are images identical - in terms of resolution, perspective (must be, given that perspective is independent of focal length...or?), image circle of optics used/not used, and "feel... or did I miss something?

 

[Chriscrawfordphoto]

Should be the same, except possibly in resolution. Depends on if the cropped section of the M9 frame has the same number of pixels as the full M8 sensor does.

 

[Godfrey]

Should be the same, except possibly in resolution. Depends on if the cropped section of the M9 frame has the same number of pixels as the full M8 sensor does.

M9 has the same pixel density as the M8 so if you're cropping an M9 photo to the same format dimensions as the M8, th results are identical.

G

 

[Roger Hicks]

DoF calculations make a number of assumptions, most of which are barely defensible. That's all there is to it.

Cheers,

R.

 

[Sparrow]

... bit radical, you'll be telling people to look at the prints and decide for themselves next

 

[pvdhaar]

What I don't understand is, that when you look at a DOF-table like dofmaster.com, there are different circle of confusions for M8 and M9. This leads to different DOF calculations for the same lens.
Why that? My naive thinking tells me that a 35mm on the M8 shows the exact image compared to the M9 just cropped. So the DOF should be the same if the image is just cropped.

The idea is that you enlarge from different sensor formats to the same output print size. A larger sensor needs less enlargement, so you can get away with a somewhat larger COC.