Canon SLR image file size

[YHwee1]

Hi canongrahers,

I own a 30D and recently found out that the maximum file size (8MB) for my picture taken in RAW format is very much smaller than the other uncompressed image format in some other systems (~20MB). This will mean that the compression ratio for 30D is set to be very high. I hope I am right to say that lower compression ratios genrally give better image qualities. There are 2 questions I have in mind.

1. Is there a way to increase my image file size larger?

2. If not, how can we print large image size say (A1) format without suffering a loss in image quality?

Hope someone can give your comments on this.

[lightning]

There are no compression in RAW format. each pixel is map to one byte of data. For those system with over 20MB (TIF), sometimes post processing is done on the pics already. A dull color pics has smaller file size compare to one which lots of color. Different ISO produce dofferent file size too.

[ykia]

RAW format does not use any "lossy" compression, so what you shoot is preserved. Your files are saved as efficiently as possible so that it doesn't use too much space.

The older cameras may be using a less efficient file saving format which results in a bigger file.

For A1 prints (A1=A4 x 8) it's about 95" along the long edge, so at 300dpi you'll need 28.8K dots. Usually 150dpi is ok for most posters. Only way to achieve this with the 30D is to upsample the pic -- do it 5% at a time for better results.

[YHwee1]

Originally Posted by lightning There are no compression in RAW format. each pixel is map to one byte of data. For those system with over 20MB (TIF), sometimes post processing is done on the pics already. A dull color pics has smaller file size compare to one which lots of color. Different ISO produce dofferent file size too.

Hi, So you mean some systems with over 20MB (TIF) format have post processing done in camera? I wonder why is that a same 8MP sensor can produce files that differs so much in size when both are taken in RAW that tries to preserve all information. Sorry, I'm rather puzzled.

[YHwee1]

Originally Posted by ykia RAW format does not use any "lossy" compression, so what you shoot is preserved. Your files are saved as efficiently as possible so that it doesn't use too much space. The older cameras may be using a less efficient file saving format which results in a bigger file. For A1 prints (A1=A4 x 8) it's about 95" along the long edge, so at 300dpi you'll need 28.8K dots. Usually 150dpi is ok for most posters. Only way to achieve this with the 30D is to upsample the pic -- do it 5% at a time for better results.

Hi, so you mean 30D cannot produce pictures of that size without upsampling of the pictures? By the way, upsampling means adding more pixels to my picture manually? Will quality be compromised in this way?

[zj2000]

Originally Posted by YHwee1 Hi, So you mean some systems with over 20MB (TIF) format have post processing done in camera? I wonder why is that a same 8MP sensor can produce files that differs so much in size when both are taken in RAW that tries to preserve all information. Sorry, I'm rather puzzled.

i assume the "other system" you refer to here is fuji rite? the s5pro does produce 20+ mb raw files when shooting at 400% dr.... based on my limited knowledge, i assume this is because of the greater dynamic range that is captured hence more detail is contained in that raw file...

[YHwee1]

Originally Posted by zj2000 i assume the "other system" you refer to here is fuji rite? the s5pro does produce 20+ mb raw files when shooting at 400% dr.... based on my limited knowledge, i assume this is because of the greater dynamic range that is captured hence more detail is contained in that raw file...

Hi,

For your information, Olympus DSLRs produces images of that size too.

[Aspect]

Originally Posted by lightning each pixel is map to one byte of data.

Just to clarify, each pixel usually maps to more than one byte.
One byte is 8-bits.
I guess most dslrs will have more than 12-bits per pixel.

[lightning]

Originally Posted by Aspect Just to clarify, each pixel usually maps to more than one byte. One byte is 8-bits. I guess most dslrs will have more than 12-bits per pixel.

Tradtionally it was like that when it was 8bit. Yes each pixel is 12bits, some 14bits, so for 1DM2 sometimes my RAW file is 10MB, provided each pixel has important info to keep. Try taking a pure white pics, a black pics and a colorful pics, their file size are all diff.

[Russ]

TIFF (Tagged Image File Format) is an uncompressed format that is "high level" in that it not only contains raw pixel data but also a lot of other information - see below. Hence the file sizes are large

TIFF can handle multiple images and data in a single file through the inclusion of "tags" in the file header. Tags can indicate the basic geometry of the image, such as its size, or define how the image data is arranged and whether various image compression options are used. For example, TIFF can be used as a container for JPEG and RLE (run-length encoding) compressed images. A TIFF file can also include a vector-based Clipping path (an outline that crops or frames the main image). The ability to store image data in a lossless format makes TIFF files a useful method for archiving images. Unlike standard JPEG, TIFF files can be edited and resaved without suffering a compression loss. Other TIFF file options include multiple layers or pages

RAW is also UNCOMPRESSED but only contains a straight data dump from the sensor, hence the file sizes are smaller. There is NO loss or compression. Making the file any bigger will not give you any more data.

[xunjas]

any software to reccommend to blow up the dimensions of the raw photos =)

[ST1100]

Originally Posted by Russ RAW is also UNCOMPRESSED but only contains a straight data dump from the sensor, hence the file sizes are smaller. There is NO loss or compression. Making the file any bigger will not give you any more data.

RAW files are definitely compressed, but the compression is non-lossy. If they were uncompressed, every RAW file would be exactly the same size, down to the byte, independent of ISO or image content. The size of a RAW file varies bcoz of compression. This compression is not image (jpeg) compression, it's data compression.

[ST1100]

Originally Posted by YHwee1 Hi canongrahers, I own a 30D and recently found out that the maximum file size (8MB) for my picture taken in RAW format is very much smaller than the other uncompressed image format in some other systems (~20MB). This will mean that the compression ratio for 30D is set to be very high. I hope I am right to say that lower compression ratios genrally give better image qualities. There are 2 questions I have in mind. 1. Is there a way to increase my image file size larger? 2. If not, how can we print large image size say (A1) format without suffering a loss in image quality? Hope someone can give your comments on this.

The RAW file is compressed, so comparing it with a TIFF file size is meaningless.

1. The 30D image is 3504x2336, that's ~8.2 megapixels. That's the maximum information you can get from a single shot. You can uprez the file as much as you want, but you won't get more than the 8.2mp you started with.

2. When printed at A1 (840mmx594mm), the maximum resolution of real data you can get from a 30D image is ~53dpi. That's if you max out the image quality on the sensor, with very good lenses and very good technique (30D max sensor resolution is 77 lp/mm). Normal handheld shots give you ~25 lp/mm, so you're really looking at ~17 dpi for an A1 image shot handheld. The picture will look ok if you step back, but will look coarse on closer scrutiny.

[Russ]

Originally Posted by ST1100 RAW files are definitely compressed, but the compression is non-lossy. If they were uncompressed, every RAW file would be exactly the same size, down to the byte, independent of ISO or image content. The size of a RAW file varies bcoz of compression. This compression is not image (jpeg) compression, it's data compression.

As long as it is not IMAGE compression, you don't lose data - it is a bit like zipping files - you don't lose data. So you cannot get any more info out of the sensor than the RAW files even if you tried. Right?

[ykia]

I work off Adobe CS2. If you start off at 4000pix and need to reach 24000pix, there's 20000pix to "add in". At 5% (or 1/20), then up-sample in steps of 1000pix (20000pix/20), i.e. 4000, 5000, 6000, etc...

Yes, the quality is compromised as you are adding in pix that are a approximation of its neighbours so that the jaggies won't show in your A1-sized prints.

Originally Posted by YHwee1 Hi, so you mean 30D cannot produce pictures of that size without upsampling of the pictures? By the way, upsampling means adding more pixels to my picture manually? Will quality be compromised in this way?