Ad
Ad
Ad
Pages: « 1 ... 6 7 [8]   Bottom of Page
Print
Author Topic: Mark Dubovoy's essay  (Read 35874 times)
Herb19
Newbie
*
Offline Offline

Posts: 14



WWW
« Reply #140 on: December 22, 2010, 08:28:29 AM »
ReplyReply

I did a few tests

http://www.datarescue.com/photorescue/freefiles/compare40d5dmkII.jpg

http://www.datarescue.com/photorescue/freefiles/5dmk2.jpg

http://www.datarescue.com/photorescue/freefiles/40d.jpg

40D / 5DMK2 - tripod - remote trigger - 1 meter from target - auto exposure - lighting poor on purpose to better see the noise. Shot in RAW, converted to jpeg at max quality with no adjustment whatsoever, ISO 800

AFAIC

- the gain boost is quite visible, maybe a bit less on the 40D, but the auto-exposure chose different parameters.
- the practical impact, at least at pixel peeping level, of the gain boost is more significant than the raw noise number indicate, probably because noisy pixels have a bigger than expected impact on the RAW conversion.
- the DOF decreases as expected (it is very visible on near tangent images of printed text, as posted earlier) at least on the 5D
- the 40D doesn't seem to exploit that DOF increase fully, but that's just a gut feeling, and DOF is bigger anyway.



Pierre,

Interesting data, nicely done. Seems indeed that gain (noise) increases at wider apertures. The change of DOF is clearly visible.
Expected to see slightly more gain (noise) increase of the 40D compared to the 5D as per DxO labs figures / smaller 40D photo sites.
Probably the difference of 0.1EV is neglectable / not visible in this test.

Please note that the DOF of the 40D is smaller because you are shooting both camera's from the same distance.

Calculated DOF for a 85mm lens on both camera's focussed on 1 meter distance is as follows:

             5Dmk2          40D

f/2.0       1.6cm          1.0cm
f/1.8       1.5cm          0.9cm
f/1.4       1.1cm          0.7cm
f/1.2       1.0cm          0.6cm

Of course these figures are approximate for standard eyesight on printed matter. However close enough for validation of this test I think.
Used the DOF calculator on the Cambridge in Colour site.
http://www.cambridgeincolour.com/tutorials/depth-of-field.htm

These distances are very close according your test shots.

So it looks that gain (and noise) is increasing towards wider apertures and still the influence of aperture on DOF remains visible towards f/1.2.

Herb
« Last Edit: December 22, 2010, 08:51:01 AM by Herb19 » Logged
NikoJorj
Sr. Member
****
Offline Offline

Posts: 1063


WWW
« Reply #141 on: December 22, 2010, 08:55:48 AM »
ReplyReply

- the DOF decreases as expected (it is very visible on near tangent images of printed text, as posted earlier) at least on the 5D
- the 40D doesn't seem to exploit that DOF increase fully, but that's just a gut feeling, and DOF is bigger anyway.
Thanks for the test!
The width of DoF doesn't seem that impacted, but I fell that the bokeh changes with the max aperture, see the blue line at left side of the ruler...
Logged

Nicolas from Grenoble
A small gallery
Pages: « 1 ... 6 7 [8]   Top of Page
Print
Jump to:  

Ad
Ad
Ad