Gamma tests -DVX100A PAL

P

pedro_emauz

Member
Hi all,
I am continuing my gamma tests with the DVXa (pal).
Parameters were:
PresetWB 5.6k; Detail: -1 Vertical Detail: 0; detail coring: -2; all colour parameters at 0; M.ped -4 ; Matrix at Norm1; Skin Dtl. OFF; V. Dtl Freq. at THIN; 25P scan; Odb Gain; f: 4.8 no ND; shutter OFF.
Exposure as kept the same on all samples.
From top to bottom gamma settings of: L (LOW); N (NORMAL); H (HIGH); BP (BPRESS); C (CINELIKE) ; CD (CINELIKE_D); CV (CINELIKE_V)

here is the pic:
gammatests.jpg


what do you think?
 
Re: Gamma tests -DVX100A PAL

Pedro,

this is interesting to see how each gamma setting reacts in a controlled environment. The whites and the blacks recieve the same amount of black, so the blacks still reflect a certain amount of light, so it is very normal that we see blacks look like gray.

But this test does not show how each setting reacts in real life.
In real life with high contrast, "High" and "CinelikeD" have the best dynamic range the DVX100A has to offer. The CinelikeD has the widest dynamic range.
 
by each gamma settingRe: Gamma tests -DVX100A PAL

by each gamma settingRe: Gamma tests -DVX100A PAL

Hi Antoine,
You are right. I did not make this test to get the most out of each individual gamma setting (then I would have to change other parameters like exposure and mped, for example), but to see exactly what were the density changes produced, mantaining the same exposure and other parameters, ie, find out the exposure latitude and charcrteristic curve of each gamma setup. This, however, relates to real life setups.

This test is purely empirical, because for one hand this scale was designed for photography, where the processed print/slide/negative would be read by a densitometer and its values ploted in a graph (gamma curve). Secondly, it´s very old, and has scratches and wear visible on the darker steps, making the results innacurate. Furthermore, I do not have a waveform monitor, so my conclusions are subjective.

What impresses me the most is the exposure latitude of this camera, the chips beeing so small(1/3"). If i remenber correctly each density step represents a density change of 1/3 stop (0.10log d). to my eye camera has an exposure latitude of 5 2/3 stops.

The low gamma setting apparently doesn´t change much compared to the normal gamma density scale, but it darkens the lighter greys and mid-tone greys just slightly, while the darker greys on boyh scales have similar densities (step #11 and higher). It is smoothing the curve at the «shoulder», while mantaining a smooth density increase at the bottom of the curve.

The normal gamma scale is for me the most linear of all. Equal density increase in all the scale steps until step 18 (6 stops exposure latitude)

The high gamma scale has identical density changes until step M (caucasian skin grey corresponding to +/- 65IRE) and then it smooths the transition into darkers steps aproximately 1 step (1/3 stop), thus reaching more into the shadows (doing exactly what you were saying it would on real life), but, as when it hits the mped value it doesn't read further, as the black level is 2 steps up (about 15 IRE) , equal to step 16 on the normal gamma chart.

The Bpress gamma is higher than the normal gamma scale by aproximately 1 step (curve more steep) on the top part of the curve and on the lower part of the curve. Also the transition beetween the middle gray section and the toe section of the scale (steps 13 and 14) is smoother, indicating a more contrasty setting, as expected, to create contrast and visual separation in low light situations. The black step 18 has separation, and its almost black, not mushy like in the normal scale.

Man this post is getting HUGE! I´ll post the rest tomorrrow. What do you guys think?
Cheers,
Pedro
 
Re: Gamma tests -DVX100A PAL

Hi Pedro,

just for fun, shoot a white building in a sunny day 7 pm with objects you want to see in the shadow without overexposing too much the white building...

I am amazed at how good the DVX100A performs playing this game with the CinelikeD gamma setting...

...f 3.4 combined with ND1 are the magik numbers...wow !
 
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