f/1.8 on m4/3, ASP-C, FF; are they the same?

Started Nov 1, 2010 | Discussions
nugat Contributing Member • Posts: 699
DOF is subjective and conventional

DOF is a subjective phenomenon and depends solely on:
--watching distance
--print magnification
--allowed size of circle of confusion

Lens DOF markings (and strangely enough on-line calculators) date back to Barnack's 1912 assumptions based on 19th century CoC standards.

On a 10x8 inch contact print looked upon from one foot a circle of 1/100 inch was considered the "sharpness" limit. This roughly translates to today's 36x24mm frame CoC of 0.03mm magnified 8x to ca A4 print (0.03 mm x 8= 0.24 mm or ca 1/100 inch).

The 19th century assumptions of eyesight strength are rather inadequate, many 20/20 vision individuals (and correction glasses wearers) will see double or triple the detail. Computer pixelpeepers demand a "pixel-level sharpness", etc etc. Therefore many believers in zone DOF and relying on lens markings and DOF calculators are deeply disenchanted with results. In fact to get at the 20/20 vision level sharpness expectations those suggestions must be tightened 2-3 times and aperture closed 2-3 stops to make CoC that much smaller (eg. 0.01mm on full frame).

All that assuming that the lens resolution is good (40lp/mm), camera perfectly steady, focus ideal and diffraction not a factor.
Good reading:

h00ligan Veteran Member • Posts: 3,102
Re: f/1.8 on m4/3, ASP-C, FF; are they the same?

Agreed. If the gf1 had ine stop better iso performance it would be a monster.

Everdog Veteran Member • Posts: 4,837

Joesiv wrote:

btw, it also seems like the GH2 "fixed" the underrated ISO values... that might also contribute to the "cleaner" higher ISO's that people are seeing. We'll have to take that into account.

I agree. I am sure they did it for marketing reasons. Some thought the GH1 was not very good at higher ISOs because they were comparing apples to oranges. I just happen to own a T2i and a GH1 and know the truth.

The other thing that hurts Panasonic is the difference in quality in these sensors. I have seen some GH1s with terrible banding at ISO 1600, and other that were perfectly clean. If anyone wants to find "bad" GH1 pictures, they are out there.

h00ligan Veteran Member • Posts: 3,102

Wouldn't f-stop be the same but T-stop be different?

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