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Old Sep 11, 2009, 9:43 AM   #1
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Default File Size Confusion A200, A350, A330

I have been reading some reviews on the new Sony D-SLR cameras the A330 etc. I read an article in Shutterbug that had me wondering something.

My A200 produces file sizes under 5MB when opened in photo shop elements and saved as jpeg Max. A Friend has the A350 and it gets file sizes around 4.8 - 5.4MB.

I then read the shutterbug article and another on line review of the A330 and it said The 10.2 megapixel (30+MB open size).......

My 10.2 A200 gets under 5MB and even my A700 doesn't come close to that.

Is that a misprint in two separate places or am I missing something. The values I got very from shooting fine jpeg (at max resolution) opened in Photo Shop Elements and saved a jpeg max files.

dave
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Old Sep 11, 2009, 9:52 AM   #2
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JPEG files are compressed, and file size will vary by content (since some content compresses better than others). If you have a lot of area with the same color, it's gong to compress much smaller than areas with more colors and detail.

As for the comment about "30+ MB open size", that's right. When you open a JPEG file, the editor decompresses it.

You've got 3 bytes per pixel in the uncompressed image (one byte each for red, green and blue). So, if you multiple 3 bytes by the number of megapixels (10.2 in this case), you come up with the open file size (how much space it's taking up in memory after being decompressed).
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Old Sep 11, 2009, 10:03 AM   #3
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Thanks for the quick and very good answer.

off to work for a long weekend of shooting.......

dave
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Old Sep 11, 2009, 10:55 AM   #4
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Quote:
Originally Posted by Photo 5 View Post
My 10.2 A200 gets under 5MB and even my A700 doesn't come close to that.
I just checked some images from my A700, and I was getting "straight from the camera" JPEG Fine file sizes of around 8MB for some outdoor scenes with lots of foilage and fine detail when using smaller aperture settings (higher f/stop numbers) for more depth of field.

Yet, I had some portraits taken at the same time that were around 5MB in size (because they were taken at wider aperture settings with a blurred background that had less detail in it). If I were to open those in an editor and save them at higher JPEG quality settings, file sizes would be even larger (provided I didn't do any editing that destroyed some of that detail, which edits can sometimes do if you're not careful).

Lens quality (as a lower quality lens isn't going to capture as much detail), content and more will impact what file sizes you see.

Another thing you'll notice is that noise can increase JPEG File sizes (since the compression algorithms interpret the noise as detail).

IOW, you've got lots of variables as to what kind of file sizes you'll get when shooting JPEG.

But, the uncompressed image size will always be the same for a given resolution (image size in pixels) when shooting JPEG (3 bytes per pixel is being taken up in memory when you open a JPEG file, regardless of how much detail you captured).
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Old Sep 11, 2009, 9:48 PM   #5
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Great follow-up answer as always makes a a lot more sense to me now. On mY A700 I am getting between 6MB and 8MB file sizes.

dave
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Old Sep 12, 2009, 5:24 AM   #6
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Note that your A700 also offers a JPEG Extra Fine option (and If you use it, your file sizes should be even larger, since it compresses images less).

Personally, I use JPEG Fine + craw (compressed raw) most of the time. That way, I've got a ready to use JPEG file, and a raw file I can convert if I need higher quality (and/or my settings for exposure/white balance were off some).
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