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This question already has an answer here:

I love viewing RAW images through Picasa, as it's a free viewer and works for all RAW files. But there's sometihng I don't like — the auto adjust/enhance feature. After opening a RAW file, the preview gets changed after a second.

How to configure Picasa so it shows only the unedited RAW file?

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marked as duplicate by mattdm, Paul Cezanne, MikeW, Itai, ahockley Aug 4 '13 at 23:23

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

1  
See the other question, but the essential answer is there is no such thing as showing an unedited raw file. –  mattdm Aug 2 '13 at 15:00
    
The short answer is that it immediately loads the embedded thumbnail, while it calculates its own result from the actual RAW data in the background and shows that once it's complete. The JPEG thumbnail will have different processing applied. See the duplicate question for more information, and this for why the JPEG preview may look "better" (or different) to the RAW image once it's calculated. –  thomasrutter Aug 5 '13 at 5:30

2 Answers 2

up vote 2 down vote accepted

Please do see the question this is marked as a duplicate of for a full answer, but just to emphasize the point I wanted to add this example. This is as close to an "unedited RAW file" as I can manage:

an "unedited RAW file"

I made it with unprocessed_raw from LibRaw. Each pixel contains the raw data for the photosite with no interpolation, and scaled to fit into an 8-bit JPEG for uploading but not otherwise.

The corresponding from-the-camera RAW preview looks like this:

from-camera preview

Which I think we can pretty much agree makes a better preview.

Those are scaled-down, obviously — let me also illustrate with some expanded samples. Here's a crop of the eye from the built-in preview. You'll notice some serious JPEG artifacts — the image out the other side of the RAW converter doesn't have these, of course, and they'd be barely noticeable with a higher-quality in-camera JPEG than is used in the preview. Anyway:

crop of eye from preview

And here is the same eye (sorry, slightly different crop) cropped from the "unprocessed" RAW, although here I've applied a levels adjustment so you can see the pixels more clearly:

crop from "unprocessed" raw

Sooooo, I think the obvious conclusion here is that Picasa is really doing the right thing after all.

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Are you sure that Picasa actually chages the RAW file? I haven't used Picasa but many (most?) RAW formats include a JPEG preview and my guess is that the first thing you see is the preview and then you see the RAW-file.

I may bee completely off here but that is how many RAW-viewers work.

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