adjusting color temperature in jpeg?


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denniskee

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#1
assuming i set the preset color balance in camera to sunny day (ie similar to film), than i shoot under a artificial light with a known color temperature.

if i shoot raw, i just adjust color temperature slider to correct the color cast.

if i shoot in jpeg, adjusting color balance or channel mixer will depend on my eyes (if got color blind, how) and the correctness of the monitor calibration.

why is it like that? why jpeg cannot use color temperature slider (is it done on purpose or limitation of technology?)

also, is there a chart to say, eg, adjusting the slider of each of the color in color balance option to certain amount equals to a certain color temperature?

sorry my bad english, hope you guys can understand what i asking.

happy cny 2006.
 

Witness

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#2
because jpegs bundle in the in-camera processing..... which permanently permanently sets linearity...that's y u cannot change the wb in the 8bit jpeg....
 

wiz23

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#3
Yo Dennis,

I think that's the limitation of jpeg, bro ... That's why for important shots, or as often as we can, we always shoot in RAW, right?

Next week we go night shoot? On boh?
 

denniskee

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Witness said:
because jpegs bundle in the in-camera processing..... which permanently permanently sets linearity...that's y u cannot change the wb in the 8bit jpeg....
but than we still do color adjustment even though we shot in jpeg right? so if, technically possible, would it not make sense to allow for color temperature adjustment like that of a raw file?:think: :confused:
 

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denniskee said:
but than we still do color adjustment even though we shot in jpeg right? so if, technically possible, would it not make sense to allow for color temperature adjustment like that of a raw file?:think: :confused:
When a WB is applied and the file compressed (algorithm and lower bit rate) in jpeg, some of the brightness/colour data have been lost or permanently altered.

Yes, you can still do colour adjustment in jpeg but, due to data lost during the application of WB and compression used thereafter, it's no longer possible to adjust the WB in the way way as what is possible in RAW file where such data are left largely untouched. The process cannot be reversed because from the compressed jpeg file, we don't know what data have been discarded.
 

Witness

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data./colours tt cannot be seen by the naked eye is discarded...and it cannot be retrived....tt's y its called lossy compression...

cheers.
 

szekiat

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#7
its called loss-less compression, if there's even such a word. Ideally, u'd not notice the difference. YMMV. Personally i shoot jpg all the time and tweak it in PS's channel mixer function. While not as flexible as a RAW WB slider, it usually gets the job done.
 

Witness

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eh i tot lossless compression is that u are able to get back all your info when decompressing it....
 

topster

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Can I suggest using the Photo filter option that is available to PS CS2.

I use it when my wb really screw up. Just use Cooling filters if your pic too 'warm' and Warm filters if your pic is too 'cold'. There's even a % bar to tweak the amount of effect.
 

theRBK

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Jpg is a lossy compression... you will lose detail to Jpg compression artifacts... the main lossless compression used in cameras is RAW compression... Tiff can be losslessly compressed but don't think cameras of today have the processing power to do it quickly...

I believe PaintshopPro has, or at least used to have, a tool which allows you to adjust the tone of an image through an interface marked with temperature... not exactly the same as changing it in RAW but useful for people who don't need too much close control...
 

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