Histogram/LCD preview question - shooting in raw

elven

I've been trying to understand this one for a while now, and I'm too lazy to go experimenting and find out through the laborious process of evaluating the results myself. Does anyone know how the histogram is generated, in relation to the raw file? I mean, from my understanding, the camera actually produces a temporary jpg on the fly and uses that to generate the histogram, as well as the LCD preview - but what I wonder about is what settings of brightness/contrast/saturation are applied to that temporary jpg to give that result? Does the camera apply the same settings to every shot for the sake of that kind of evaluation?

It also leads me on to wondering about the settings in ACR: if I set every slider to neutral, does that give me exactly what was recorded, and if I was to have taken the same shot in jpg would it automatically lighten up shadows, increase the blacks, adjust brightness/contrast/exposure according to the histogram like bridge tries to do in its previews, or again, does it apply the same settings to every single shot, given that you haven't selected a 'mode' like 'high saturation' or something?

I'm not entirely sure I've managed to write down the actual question that was in my head but I'll see if anyone gets the idea anyway...

Dimy

I could be wrong, but I always thought it would use the same processing steps as if you were shooting in jpg and thus have your raw automatically processed to jpg in order to calculate the histogram when shooting RAW.

Ehm... hope you know what I mean, but as I said that's just what I thought how it's done, not fact :rolleyes:

bp_me

Even if the camera doesnt do the jpg conversion, the raw file is essentially a list of pixels, their colours and their brightness. I can't see why the camera couldn't read these brightness values directly.

elven

It doesn't show you the histogram for the raw data, it shows you a histogram for the image after the in camera settings have been applied, as theyw ould be if you were shooting jpgs.

Here's a thread that kind of explains it: http://photography-on-the.net/forum/showthread.php?t=97142&highlight=raw+histogram

I suppose it answers my question that it just applied the same settings to every shot and doesn't try to adjust them individually. That's just ACR and lightroom, from the looks of things. ACR in photoshop CS2 seemed to pick up the camera settings, but the one with CS3 beta just makes up its own mind and usually gives horrid results.

Roen

The image u see on screen on your camera is a low res jpg embedded in the Raw, it's in no way a good indicator of what the finished print may look like, what I am not sure about is whether the histogram is from the Raw or the displayed Jpeg.

I have noticed that some onscreen previews seem fine, but when I open the file at home it seems underexposed.

mtracey

The image on the lcd always looks better than the raw file that comes off it.
Pity