Questions about raw, tiff, jpeg, and DNG

Started Mar 27, 2013 | Questions thread
Tom Axford Veteran Member • Posts: 3,772
Re: Questions about raw, tiff, jpeg, and DNG

clear glass wrote:

I know raw is just the data.

Here's my question. Specifically, I'm shooting raw with Olympus cameras XZ1, XZ2, and E-LP5.

If I translate the raw into tiff or JPEG with the Olympus Viewer, I have the option to work on it (change contrast, color balance, etc.) before the translation to tiff or JPEG is complete.

Here's my question: Am I losing raw data (information) if I make no changes during translation; will there be less flexibility once the file comes out of Olympus Viewer as a tiff or JPEG? To work on a tiff or JPEG, I currently use Elements 6.

Any program that converts RAW to a viewable image will throw away some of the data in the conversion process. That viewable image must be saved as a TIFF or JPEG normally. But most photographers who shoot in RAW like to keep the RAW images as well in case they want to go back and reprocess them as that may give slightly better quality than processing a saved TIFF or JPEG.

I also know that JPEG changes do entail loss of raw information each time the file is saved; is there any of this in tiff?

JPEG images incur a loss of information every time a JPEG is saved. This is because the JPEG is highly compressed and a little of the data is lost in the compression process - much less than you would expect because the algorithm used is extremely clever. How much is lost depends on the JPEG quality (usually a number 1 to 100 that you can set in the program that saves the JPEG).

TIFF images involve no compression and hence no loss of data occurs when the TIFF image is saved. If you want to save an image knowing that you will return to it to continue editing it, TIFF is much better (but the image file is a lot larger than a JPEG). When you read a TIFF file you get an image identical to the one you saved. This is not the case for JPEG.

Is DNG superior to tiff for keeping possibilities for development?

Not in terms of the data kept, but more programs know about DNG than some proprietary RAW formats, hence it may be better in the long term.

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