Histograms

[britonk]

Can anyone explain to me why the histogram displayed on my D50 just after taking a shot is completely different to that displayed in Photoshop?

I have been learning how to use the histogram to ensure shots are exposed properly (to ensure there are no under-exposed low-lights or overexposed highlights) but when I have got exposure right according to my D50s histogram then load the exact same pic into Photoshop it displays a completely different histogram.

Is this to do with colour space and perhaps caused because I am not shooting RAW?

Thanks,

Brian

 

[The_Traveler]

I have no idea but try shooting in raw and then opening up the image without allowing the raw converter to make any changes (eliminate the deafult changes) and see what happens.

 

[markc]

Is it drastically different? If they are using different algorithms, I could see them not being exact, but I would expect them to have similar characteristics. If it's completely different, something seems wrong. A strongly overexposed image in camera should not show as underexposed in PS unless something has changed.

 

[ksmattfish]

It doesn't surprise me that they are different, although if it's exposed right in the camera, it should look okay in PS, particularly jpeg. I know that my 20D creates the histogram it displays from a jpeg thumbnail, even if I'm shooting raw, so what it displays on the back of the camera isn't always exactly the same as if I were to look at levels in PS.

Are you lining the histogram up to the left or right edge on the back of the camera, and then finding in PS that it's really slightly past the left or right edge? Luminosity histograms do some averaging that sometimes isn't very accurate. To be completely sure you haven't gone past either edge of the histogram you need to look at the individual RGB channels. If your camera only has a luminosity histogram (like mine), you need to give the edges of the histogram a little fudge room, in case one of the channels is over (or under).