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RAW (newbie questions)

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Offline CanonBlue

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RAW (newbie questions)
« on: 30 / May / 2009, 08:55:11 »
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So, I've heard that raw files give better quality photos. I've never used them before and I don't really know how to process them, etc. (Note: I have a Mac) So far I've noticed that iPhoto won't let me import them. I just have a few general questions:

1. I've seen some references to being able to change what types of raw files are saved on the camera. Right now I think its saving .crw files. What's the best type of file to use and how do I change that setting? I know how to turn raw on and off (by hitting the Disp button in chdk mode).

2. When I have raw files on the camera, they don't seem to show up so that I can view and erase them. I've seen some references to purging raw files. Is that the only way to do it? Is there any way to delete them one at a time? If not, how do you purge raw files?

3. What's some good, preferably free, software for processing raw files on a Mac?

The thing is that I have exams coming up so I don't have much time to play with this, but then I'll have some chances to take good photos right after exams. So I'm thinking that if I take any grand shots at that point, maybe I should take them in Raw and at least have the files so that I can try to process them later. Hopefully I can do that much without necessarily having to learn how to process them now. So for that, I want to know what format I should be using, at least.

Thanks!
« Last Edit: 30 / May / 2009, 08:59:02 by CanonBlue »
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Offline Microfunguy

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Re: RAW (newbie questions)
« Reply #1 on: 30 / May / 2009, 09:32:09 »
Quote from: CanonBlue on 30 / May / 2009, 08:55:11
I've heard that raw files give better quality photos.


Was that referring to large-sensor digital SLR's or 10-bit raw on CHDK-supported compact cameras ?



David
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Offline CanonBlue

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Re: RAW (newbie questions)
« Reply #2 on: 30 / May / 2009, 12:40:45 »
I have a powershot SD1100 so i'm talking about the compact cameras. I really know nothing about raw except that the files are bigger.
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Offline Microfunguy

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Re: RAW (newbie questions)
« Reply #3 on: 30 / May / 2009, 13:33:00 »
Quote from: CanonBlue on 30 / May / 2009, 12:40:45
I have a powershot SD1100 so i'm talking about the compact cameras.


What I meant is, are the comments you have read about better image quality  referring to large sensor digital SLR's or is it claimed that CHDK raw (on compact cameras) gives better image quality ?

Be aware that Canon's least-compressed JPG images are pretty good and produced without any effort on your part.

Because raw images are a lot bigger it also means there is some delay while they are saved and continuous shooting rate is therefore slower.

Although it may seem prudent  to have raw versions of your images 'just in case', will you ever get around to playing with them ?

Try taking a few raw images in difficult situations.
Hopefully others can recommend suitable editing software and you can decide if it is worth the effort.

I do not bother (or use a digital SLR for 'valuable' images).

One useful feature of raw is you can correct white balance.


David
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Offline CanonBlue

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Re: RAW (newbie questions)
« Reply #4 on: 30 / May / 2009, 13:44:50 »
Quote
What I meant is, are the comments you have read about better image quality  referring to large sensor digital SLR's or is it claimed that CHDK raw (on compact cameras) gives better image quality ?

Specifically, I had heard that its better to shoot in Raw if you want to do things like tonemapping and HDR. I don't know if those comments were referring to a compact camera, though.
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Canon's least-compressed JPG

Is there a choice of compressions? I have my camera set to superfine, so I think that's the best quality it can do.

Quote
Although it may seem prudent  to have raw versions of your images 'just in case', will you ever get around to playing with them ?

I wasn't planning to do it for every shot, but maybe only things like big wide open scenes of touristy stuff (doing some travel around Europe soon). I don't know if its really worth it... I was thinking of things like the canals in venice that I might want to try tonemapping later...
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Offline Microfunguy

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Re: RAW (newbie questions)
« Reply #5 on: 30 / May / 2009, 14:08:32 »
Quote from: CanonBlue on 30 / May / 2009, 13:44:50
Is there a choice of compressions?

Yes.

Quote
I have my camera set to superfine, so I think that's the best quality it can do.

That is what I was referring to and the colour accuracy of the JPG's.

People seem to spend a lot of time trying to get comparable results with the raw images.

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Offline fudgey

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Re: RAW (newbie questions)
« Reply #6 on: 31 / May / 2009, 04:20:28 »
RAW (and DNG) are most useful for scientific purposes and for those users who like to routinely put all their good photos through image processing tools for color and exposure adjustment, noise reduction, sharpening etc.

But even then it's possible that the color matrix approximated for your camera in our RAW tools is so bad that you won't get good results (we don't have all the information available to the camera firmware JPEG encoding process, so it does a better job developing RAW to JPEG).

Those 2 extra bits are not cruicial for HDR, because you will have to bracket multiple photos for your HDR's no matter what (10 bits is not nearly enough for high dynamic range scenes...unless it's just tonemapping for weird effects you're after -- you can do that to any 8-bit image).

Typically Canon's development process is pretty good and nicely fits these tiny sensors with ridiculously many noisy pixels hidden inside inexpensive optical parts and is more than enough for most users and uses, including HDR bracketing. The best JPEG quality truly is pretty good. You can quantify that by comparing file sizes... JPEG resolution is slightly lower than RAW (edge pixels are cropped) and it removes 20% of bits, and it compresses.

RAW for my cam is about 9 MB (i.e. around 7MB if you ditch those 2 bits) and high detail well exposed superfine JPEGs are up to 5 MB. In my opinion that's very light compression (but RGGB->RGB interpolation triples uncompressed file size causing equivalent PNG to require 13 MB, but I don't know how much that affects this comparison...after all no new information can be created in that process)
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Offline CanonBlue

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Re: RAW (newbie questions)
« Reply #7 on: 31 / May / 2009, 04:57:05 »
Thanks, that explanation was helpful... So maybe its not really worth me messing around with Raw. In that case I guess I should at least make sure I know how to delete the raw files in case I take some by accident (its too easy to turn raw on and off without noticing) and want to free up the memory card space.

Also, how do I change it between DNG and CRW? I think I saw that the raw purge only works on dng?
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Offline CanonBlue

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Re: RAW (newbie questions)
« Reply #8 on: 31 / May / 2009, 11:23:06 »
Is there a way to disable the display button toggling raw back and forth? Its too easy to turn it on by accident and then I can't seem to delete the raw files if I'm not near a computer.

Also, was the forum down for the last hour or so? I kept trying to come here and getting a message that the account had been suspended. Had me worried for a minute there.
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Offline fudgey

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Re: RAW (newbie questions)
« Reply #9 on: 31 / May / 2009, 13:13:32 »
Quote from: CanonBlue on 31 / May / 2009, 11:23:06
Is there a way to disable the display button toggling raw back and forth? Its too easy to turn it on by accident and then I can't seem to delete the raw files if I'm not near a computer.

No. Configurable shortcuts is a long standing feature request, not implemented yet. But you'll probably do that less and less when you figure out the alt mode stuff better and if you don't, you could remove the shortcut by modifying CHDK source code and building your own version.

Quote from: CanonBlue on 31 / May / 2009, 11:23:06
Also, was the forum down for the last hour or so? I kept trying to come here and getting a message that the account had been suspended. Had me worried for a minute there.

Probably maintenance related to the inactive zero post user purge.
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