Visit MPB Visit MPB Visit MPB

Why the sudden reduction in file size?

Deecy
Posted 04/05/2008 - 23:00 Link
Since getting my K10D [about a year ago] my average jpg file size has been around 9mb - up until 2 weeks ago, now out of a series of around 400 images the average has fallen to 3mb.

The largest file from a set 2 weeks ago was 13mb, the largest file this week is 4.5mb

Myself & my partner both have K10Ds and this issue is similtaneous to both cameras. Which seems to point to something other than the camera!

The settings on each camera are always at a constant at 10mp [3 star jpg quality] we use the same set of lenses - no changes there.

Shooting RAW+Jpg the RAW file is 9mb the jpg 2mb

One of our home computers runs Vista, a recent addition (last 3 weeks) we use this PC to upload the images but having tested some images taken this evening uploaded to a PC running XP the issue remains.

We've reset factory settings on one camera, this had little or no effect on the file sizes.

The only other factor I can think of is the memory cards, we re-use these every week, [re-formatting before each new job] ...

Does anyone have an idea as to why the file sizes are suddenly reduced?
www.blessingphotography.co.uk

2x K20D, 2x K10D, istDS, 2x AF 540FGZ & Pentax lenses + back-up kit
johnriley
Posted 05/05/2008 - 00:05 Link
If simultaneously two different cameras are behaving in a new way then certainly it cannot be the cameras.

However, a JPEG file from the camera can't be more than 4.5MB and when opened on the PC might well be 18MB or more (I haven't checked the exact fugures). When you save the image after opening it save it as a TIFF, which is an uncompressed lossless format.

The only thing I can think of is that perhaps you are saving the files after they have been opened as a JPEG and the Vista OS or your editing program is applying some default compression that you need to change.
Best regards, John
Deecy
Posted 05/05/2008 - 10:06 Link
Thanks for the reply, it is baffling me!

The 1st time it happened: the images straight from the cameras are uploaded to my laptop running vista, the average file size was 4mb.

The second time it happened the images straight from the cameras were uploaded to a PC running vista, average size 4.5mb.

Last night [as a control] we took images, uploaded them straight from the cameras to a PC running XP, average file size 4mb.

The images in all cases are literally put into a folder [hard-drive] no editing at all, the folder contents are then copied into another folder [PC] - these are then get edited. I've never 'saved as' anything, always working in jpeg.

From what you've said it certainly appears to be something that happens outside the cameras, it can't be a coincidence that 4.5mb is the biggest file I'm getting.

Does anyone know if the loss of file size will affect the quality when blown up? I've looked at a pre-problem [9mb] & post-problem [3mb] image in PPX at 600% magnification & the difference isn't that vast ...
www.blessingphotography.co.uk

2x K20D, 2x K10D, istDS, 2x AF 540FGZ & Pentax lenses + back-up kit
Unlocker
Posted 05/05/2008 - 10:33 Link
It's down to compression ratios me thinks. The more detail that is in the photo, the larger the file.

How? Well imagine a shot where half of it is pitch black. Instead of recording every single detail for every single black pixel, its compression could say 'this whole area is black'. Then, instead of recording the same amount of data 5 million times, it can then only record it once, then the computer draws it 5 million times.

Dunno if i made sense there, wasn't sure how to word it, but they do use those kind of techniques compressing movies onto DVD to help save space (in the above example, imagine that 25 frames a second and you can imagine the amount of data saved!).

Thats why some shots are 3mb, some 2mb, some 4mb. Not all file sizes are the same because not all shots are the same, and they are all compressed differently depending on content.

Hope I made sense there!
George Lazarette
Posted 05/05/2008 - 11:27 Link
Are you saving to a folder with compression switched on? It seems the most likely explanation.

G
Keywords: Charming, polite, and generally agreeable.
iceblinker
Posted 05/05/2008 - 11:33 Link
Deecy wrote:
I've looked at a pre-problem [9mb] & post-problem [3mb] image in PPX at 600% magnification & the difference isn't that vast ...

You've got it the wrong way round. 9 Mb is not pre problem. 9 Mb is the problem. As John said, a JPEG from the camera can't be larger than 4.5 Mb, so something is going wrong for the file size to double.

Some program that you are using must be saving the file in a different format and padding it out. I would use it differently, or use different software.
~Pete
Mongoose
Posted 06/05/2008 - 12:53 Link
iceblinker wrote:
Deecy wrote:
I've looked at a pre-problem [9mb] & post-problem [3mb] image in PPX at 600% magnification & the difference isn't that vast ...

You've got it the wrong way round. 9 Mb is not pre problem. 9 Mb is the problem. As John said, a JPEG from the camera can't be larger than 4.5 Mb, so something is going wrong for the file size to double.

Some program that you are using must be saving the file in a different format and padding it out. I would use it differently, or use different software.

Ice is right, a JPEG straight out of the K10D at 10MP *** should be about 4Meg give or take a bit.

Are you sure you haven't opened and re-saved the previous ones? A 10MP JPEG at minimum compression from a photo editor may well come up at about 8-9MB, but the camera shouldn't be producing anything bigger than 4.5 at the outside.
you don't have to be mad to post here



but it does help

Add Comment

To leave a comment - Log in to Pentax User or create a new account.