Physcam Exposure

[RErender]

We've been having some debate about how the physcam exposure is working. In a real camera Fstop changes have an affect on the contrast of the exposed image. Some of our team believe they have seen this affect also in the physcam. I have tried to validate this but in my testing it seems that all combinations of F_stop/shutter speed and ISO can be adjusted to produce the same exposure with all mixtures of settings and the same resulting contrast.

Is my testing flawed or is this what is to be expected?

[peterguthrie]

As far as I know the aperture on a real camera should not have any effect on contrast. As no real lens is perfect though, maybe you would see a difference stopped down compared to wide open. The perceived lower contrast wide open (at low f-stops) is probably because the image is not as sharp.

I'm pretty sure the vrayphysical camera doesn't simulate this (at least I hope not!)

[mdi]

As far as I know the aperture on a real camera should not have any effect on contrast. As no real lens is perfect though, maybe you would see a difference stopped down compared to wide open. The perceived lower contrast wide open (at low f-stops) is probably because the image is not as sharp.

I'm pretty sure the vrayphysical camera doesn't simulate this (at least I hope not!)

agree..

the only thing that should effect contrast would be super bright light and a fast shutter. Opening the aperture will only let more light in (and effect DOF).

Although (in the real world) if you have a lens with a very wide aperture (say 1 to 1.4) then somtimes light can bounce around in the lens and the final photo can seem a little washed out, but this should never happen in Vray though

[mdi]

Edit...also, if you exclude effects such as DOF/MB, the same exposure can be acceived by many variations of different shutter and aperture.

[RErender]

Not ever being any more than a point and shoot photographer I am not totally familiar with the ins and outs, I guess (through a quick google study) that it is more the relation ship between what speed film can be used with what F-Stops "Greatest contrast at lower F-stop and 200 asa, greater saturation at lower F-stop 800 asa" . I wonder if this is modeled into the physcam at all? As far as I can tell it is not, but I'd like Vlado's confirmation or correction.

[visumporec]

When I take photo of environment with significant distance a proffessional photographer suggest me
to use F-stop value from F11-F22 to get better contrast of details in distance.
Of course, shutter speed would be lowered...

[mdi]

When I take photo of environment with significant distance a proffessional photographer suggest me
to use F-stop value from F11-F22 to get better contrast of details in distance.
Of course, shutter speed would be lowered...

A high f number is going to be better for an environment shots because the higher the f number the less DOF will be visible, so it would have better detail (next to no DOF = sharper image). But with the vray cam its null point, because you can simply turn DOF off.

but I still dont think it would effect contrast much/or at all


you used to be able to buy high contrast film...but that was film not vray

[Neilg]

you used to be able to buy high contrast film...but that was film not vray

And photoshop/post work isnt good enough?

[RErender]

I was really hoping to get a definitive answer so I could tell my co-worker one way or the other.

[vlado]

The physical camera does not affect the contrast of the image, only its brightness. The contrast can be controlled with the Color mapping options separately.

Best regards,
Vlado

[visumporec]

I think that contrast of image depend of sun and camera position

[mdi]

And photoshop/post work isnt good enough?

ofcourse it is, didnt say it wasnt

[RErender]

Thanks Vlado, I think I will be able to convince him now.