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01/26/2006 03:34:34 PM · #1 |
I just noticed when I saved a 5Mb RAW file as a PSD, the PSD file was 17MB.
I thought RAW had about as much information as a picture could have, why is the PSD file so much larger (without any adjustments)?
just curious.
Edited for spelling... (I can't wait til my spell checker for Firefox is updated so I can use it again)
Message edited by author 2006-01-26 15:40:27. |
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01/26/2006 03:36:49 PM · #2 |
| Doesn't Photoshop resample the colours and stuff when you save it to that? |
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01/26/2006 03:39:13 PM · #3 |
You'll also notice that working in-camera, a TIFF file is substantially larger than a RAW file. The RAW file is just pixel data. The converted files also encode what's to be DONE with that data; the color adjustments, the sharpening, the contrast, whatever, in a much more complex and malleable form.
Take a look sometime at how much larger a MSWord file is than the exact same file in .txt format...
Could it be done more efficiently? You'd think so. But this is a fact of life, at least currently. I certainly notice the same thing.
(note: very layman's explanation here, I'm sure the tech weenies will hammer me on it)
R. |
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01/26/2006 03:39:34 PM · #4 |
The way I understand it, is that PSD files are based on the TIFF file system, which as you may know if you have ever shot with your camera in TIFF mode are much larger than thier RAW cousins.
There are a few simple reasons for that... RAW files, are unprocessed data based on several layers of greyscale data. TIFF files (PSD files) assign each pixel not only the greyscale data, but also color info for each and every pixel.
Notice this is a very simplistic explanation, but hope it explains at least a little as to why the PSDs are bloated.
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01/26/2006 03:46:39 PM · #5 |
Quickly,
RAW files are usually compressed, also they contain just the sensor greyscale data.
For each pixel on the array, it gets post processed to provide 3 colour values per pixel (bayer interpolation)
Ignoring the compression, that's a 3x increase in size right there.
Also, typical RAW data is 10 or 12 bit, while the PSD files are either 8 or 16bit. If you go for a 16 bit file, that's another 1/3rd increase in size over the original 10/12 bit file.
Once you start editing it at all, you'll shift some of the colour data across that whole 16bit space.
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01/26/2006 03:51:17 PM · #6 |
I think (I'm not sure on this one) that most DSLRs capture information at 12 bits per pixel, whereas TIFFs and PSP files record three 8-bit channels - one each for red, blue and green. Plus, there's all the extra Photoshop-specific information recorded as previously stated.
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01/26/2006 03:52:02 PM · #7 |
fascinating, thanks all :)
now if RAW is so much better than anything else why don't formats like PSD and TIF use the same kind of encoding scheme? |
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01/26/2006 03:56:35 PM · #8 |
Originally posted by Megatherian:
fascinating, thanks all :)
now if RAW is so much better than anything else why don't formats like PSD and TIF use the same kind of encoding scheme? |
This question doesn't make a whole lot of sense.
RAW isn't better than anything else as a storage format. It is just unprocessed info.
The advantage is that you get to choose how it is processed, rather than being stuck with what comes out of the camera.
It would be like saying a pile of bricks is so much more efficient and space saving than a house built from those bricks.
Message edited by author 2006-01-26 15:57:31. |
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01/26/2006 04:08:08 PM · #9 |
Originally posted by Gordon:
Originally posted by Megatherian:
fascinating, thanks all :)
now if RAW is so much better than anything else why don't formats like PSD and TIF use the same kind of encoding scheme? |
This question doesn't make a whole lot of sense.
RAW isn't better than anything else as a storage format. It is just unprocessed info.
The advantage is that you get to choose how it is processed, rather than being stuck with what comes out of the camera.
It would be like saying a pile of bricks is so much more efficient and space saving than a house built from those bricks. |
sorry, I guess I'm just a bit confused on it all a bit still. I was under the inpression RAW was "the best" "format" because I seem to have the most control over the image, that's what I thought the point of shooting RAW was. Since the file is so much smaller and offers so much latitude it seems (to me at least) like a good way to structure a file. |
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01/26/2006 04:15:55 PM · #10 |
Well, it's the best format for a specific job. It's not 'best' for everything. It's not best when you need to shoot a large amount of small files for web display, for instance. RAW is the best format for image capture where a relatively small amount of information can be used to produce a very high quality file...work and info goes into it afterwards rather than in the camera. RAW is dependent on software to transform it into something useful, whereas an in-camera TIFF is huge but useable straight off, without additional processing.
Originally posted by Megatherian:
sorry, I guess I'm just a bit confused on it all a bit still. I was under the inpression RAW was "the best" "format" because I seem to have the most control over the image, that's what I thought the point of shooting RAW was. Since the file is so much smaller and offers so much latitude it seems (to me at least) like a good way to structure a file. |
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01/26/2006 04:18:32 PM · #11 |
Originally posted by Megatherian:
sorry, I guess I'm just a bit confused on it all a bit still. I was under the inpression RAW was "the best" "format" because I seem to have the most control over the image, that's what I thought the point of shooting RAW was. Since the file is so much smaller and offers so much latitude it seems (to me at least) like a good way to structure a file. |
The image from your sensor has to get processed, one way or another to be a useful, colour image. All current digital cameras (except foeveon) are greyscale cameras. They don't capture a colour image.
To get that colour image, the sensor data gets processed. That either happens on your camera, with little or no input from you, or later on your computer with a lot more control, thought and fine tuning.
But either way, to get a useful image, the sensor data needs to be processed.
RAW gives you access to the basic (raw) materials to create a good colour image.
JPG has those choices made for you in camera.
Once the image is processed, it is harder to adjust things.
So RAW is the best starting point. But it isn't a good format to store processed images in - you'd have to reconvert it every time to get a useable, viewable result. |
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01/26/2006 04:22:54 PM · #12 |
Is there an echo in here?
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01/26/2006 04:25:13 PM · #13 |
Originally posted by Megatherian:
I just noticed when I saved a 5Mb RAW file as a PSD, the PSD file was 17MB. |
Adding layers will make files grow fast. My files generally start out at about a little over 2 megabyte .jpg files but after I convert them to .tiff and add a few layers they quickly grow to 40-60 megabytes. Print files are a lot larger.
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