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Adjusting Color & Exposure
In Adobe Photoshop
There are basically three file formats to choose from in digital capture:
and RAW (any or more of the following extensions: .crf, .nef, .raf, .orf, .mrw, & .thm)
JPEG is the most convenient file format for many photographers.
Pros: It offers small file sizes which results in more images per card, and faster write speeds (you won't be waiting around as much after shooting bursts). Also, if you save at a high enough quality, there is no visible loss of information.
Cons: The image loses information every time you save it as a JPEG. To save file space it finds very similar pixels and makes them the same pixels. The tolerance of what defines "similar pixels" is set by the JPEG "quality level." The higher the quality, the higher the tolerance, and less information is lost to posterizing.
Posterizing is the phenomenon where gradients no longer maintain a gradient. Instead, pixels "group up" into a limited range of colors, and you have solid blocks of colors with hard, defined lines.
Another con is that it locks down exposure and color balance. If you set the incorrect exposure (or your automatic camera did) or you have the incorrect white balance setting, too bad! That information is set, and can only be changed by "recreating" the information in photoshop. That is a difficult process, which is also the subject of this tutorial, and results in poorer information.
TIFF is a format that I will most likely never use again, here is why:
Pros: It is lossless, unlike JPEG, there is no compression of the data. This is important if you are going to need to alter that info.
Cons: Horribly large file sizes! Around 7-9 times larger than a high-quality JPEG. Also, just like JPEG, it locks down exposure and white balance, making it hard to correct for underexposure, and near impossible to correct overexposure.
Also, and this is important: never save images as TIFFs if you have altered them in Photoshop, and they are layered. Save them as a Photoshop Document (.psd). Always!
The only way I go these days!
Pros: It allows you to overexpose two stops, and underexpose almost three stops! It sets nothing into "stone," including white balance. You can change the white balance temperature of the image (in degrees Kelvin) to anyhthing from 2000-9000 K!
It remains in 16-bit color (billions of colors instead of millions)! Millions of colors (8-bit) is fine for printing (any more color won't print anyway), but you'll want the 16-bit if you shot it wrong. That extra information is key to getting a good image if you shot it wrong.
RAW blows TIFF out of the water, NO information is lost, including the amount of color.
Cons: There is only one, but it is considerable. Large file sizes. It takes up more space and takes longer to write than JPEG. My solution: buy more cards, and/or a digital wallet like SmartDisk's FlashTrax.
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