I'm not crazy, right? Pushing the ISO

[takethislife5150]

So I shoot for a local sports news agency, and my boss was trying to tell me theres a trick where you can double your ISO. I shoot with a canon rebel XS, so I know that the ISO tops out at 1600, but he was telling me you can double it to 3200 by shooting in Aperture Priority with the EV at -1

I'm correct in thinking thats not true right?
I didn't tell my boss he was wrong, never tell your boss he's wrong, haha.

or is this a well kept secret that I don't know about?

[LoveDSLR]

From Luminous-landscape forum Canon Highlight Priority - Luminous Landscape Forum:

"More precisely, if you have the camera set to ISO 200 and HTP, then the RAW image is exactly the same as if you had shot at ISO 100 with -1 EC.

The ironic thing, which shows how screwed up these big corporations get, is that it is not available for ISO 3200 on the 40D, yet ISO 3200 IS ISO 1600 under-exposed by one stop - they just double the numbers, tossing away a stop of highlight headroom."

HTP=Highlight Tone Priority.

[dcclark]

"Pushing ISO" is a well-known technique. It's not really a good technique when it comes to image quality, but if you need that extra light sensitivity, you can kind of fake it by pushing the ISO. It's fun to try, but not something I'd use regularly.

[jdepould]

Your boss still shoots film, probably. He's talking about push processing, which is easier to do with film. Even shooting raw, underexposing by a full stop is going to make for really ugly images.

[inkista]

Not sure that there's much more difficulty in pushing digitally than with film. All you have to do is shove a slider around in LightRoom, after all.

I underexposed by three stops and digitally pushed the following image by a stop and a half:



Canon XT/350D. EF 135mm f/2L USM. iso 1600, f/2, 1/80s.

The noise isn't pretty, but at least I got the shot with a minimum of motion blur. I was maxed out on iso and aperture. The room was darkened for a slide presentation, so I was literally shooting in the dark, and the XT maxes out at iso 1600.

Sometimes digitally pushing may be the only option you've got, and at websizes, it can still give passable results. Not to be preferred over properly exposing, though.

BTW, if you're using 1/3 stop ISO settings, your camera's doing digital push/pull processing to achieve those steps. Only the full-stop settings are done by gain across the sensor; the others are done in software. This is why some of those mid-step ISOs can actually exhibit more (or less) noise than the full-stop settings. It's kind of an argument for turning off 1/3-stop iso steps.

[takethislife5150]

Well I know about pushing it in RAW, but we shoot in volume, so RAW is not an option,
thanks for the input guys

[OsmosisStudios]

I've pushed some RAW files a full 2-stops. As long as it was taken at a reasonable ISO, its not too noise. 1 to 1.5 stops is decent. Anything below 1 is fine IMO.

[inkista]

Originally Posted by takethislife5150

Well I know about pushing it in RAW, but we shoot in volume, so RAW is not an option,
thanks for the input guys

Well, you can push the same slider on a JPEG file, it's just that you run more risk of creating color halos when you adjust the exposure too far. If you're within a stop, it'll probably be all right. Not sure I'd want to try pushing/pulling farther than that with a JPEG, though.