Digital push processing?

GREAPER

I was speaking with a photographer from my club the other day and he presented an idea I had not heard before.

We have all heard the advantages of shooting in RAW explained many times, and on of the advantages is supposed to be 2+ stops of exposure lattitude after the shot is taken without the introduction of noise.

He suggested that it is possible to use that lattitude to your advantage. Intentionally shoot 2 stops under exposed when you need a faster shutter speed than the ISO will allow rather than crank the ISO from say 200 to 800. 800 is likely to introduce a good bit of noise or grain to your shot which may not be desirable.

Just in case my rambling is not making sense, an example.

Shooting a bird in the shadow of a tree through glass, fstop of 300 mm lense set to f5.6 (your largest aperature) Camera's metter says 1/15th for proper exposure. Glass will bounce back flash. Too slow to freeze the birds quick movements.

Normal Solutions:

Shoot at 1/15th and accept motion blur as a cool effect.

Crank ISO to 800, change shutter speed to 1/60th and have a better chance at freezing small movements and accept the higher grain or noise level.


Suggested solution:

Leave ISO at 200, Change shutter speed to 1/60th, set quality to raw. shoot the shot which will be underexposed by 2 stops. In post make the needed exposure correction.


My question is will this work or will you actually introduce noise making the adjustment? Will it come out any better than the ISO 800 shot?

Andy

hit or miss for me
i've tried it

depending on the shot, uppping by 2 stops in raw can add more noise than shooting at the higher iso in the first place.

as for me, i'm digging iso 800 and 1600 on the cmos canon sensor, but i'm not shooting for razor sharp birds etc that some folks are. i have printed many shots at iso 800 and 1600 and the 8x10s are great and 11x19s even are quite good.

would love to hear other folks' experience!

mercphoto

andy wrote:

depending on the shot, uppping by 2 stops in raw can add more noise than shooting at the higher iso in the first place.

I can beleive it. There is a noise floor for the sensor that is constant, regardless of ISO setting. Underexposing means there is less light hitting the sensor. This means the light registers less, and thus the inherent noise is a larger percentage of the image reading. Now you go into Photoshop and you up the exposure of the image, which is a mathemtical multiplication. That cannot distinguish between signal and noise, so the noise is multiplied as well. This is basically the same thing as adjusting the ISO in the camera, which applies an amplification to the signal coming off the sensor, which also amplifies (multiplies) the noise, which is where the grain comes from.

Lunch still isn't free.

I haven't tried any high ISO shots. Now I want to.

-- Bill

DoctorIt

I tend to do this routinely, but rarely a full 2 stops. When shooting sports or moving wildlife, I'll shoot in Aperture Priori and dial in -1 stop of exposure compensation to get the higher shutter speed, then push it back in PS. Seems to work pretty well for me.

jimf

DoctorIt wrote:

I tend to do this routinely, but rarely a full 2 stops. When shooting sports or moving wildlife, I'll shoot in Aperture Priori and dial in -1 stop of exposure compensation to get the higher shutter speed, then push it back in PS. Seems to work pretty well for me.

I can't say I do this all the time, but in difficult lighting situations I certainly do; and I too use -1 stop. You're really pushing the limit pushing it up +2 stops in post-processing, while +1 stop you can pull out very easily.

bham

Yes I have done this also and not in raw and not 2 stops, but about one stop. It has worked well for me. I have done this for basketball. I have done comparisons at ISO 3200 with no post processing compensation vs ISO 800 and 1600 with post processing. To me I saw less in the 800 and 1600, so that is how I shoot them now. I switch between the two depending on where I am on the court and how much reflection of light I am getting off of the court at that spot.