Getting confused by image size...

Lyndsey

Lyndsey

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Hi All!

Hoping for someone to explain this to me if possible - I am easily confused!!!

I use a Nikon D700 and Photoshop for editing...

I understand that the D700 has a 12.1 megapixel sensor

As an example I have just opened an image from it in Photoshop - In the bottom left corner of the screen it says Doc: 34.5M/34.5M

Without doing any editing on the photo, if I 'Save As' to a different location at Quality:12, under preview it says 5.1M... If I then check the 'properties' of the file it has saved as a 5.12mb file...

This seems to be quite a small file size?

Just wondering if someone could explain these numbers to me?!! :)

Thanks in advance,

Lyndsey
 
File size is determined by file type and compression. For the same image, saved as a jpeg it can vary by a significant amount depending on the quality (compression) setting. The lower the quality the smaller the file size. I'm guessing the 5.1M you are seeing is for a jpeg. If you have shot the image in raw (a .nef file for Nikon) then the file size on disk will be larger than a jpeg typically between 11Mb and around 18Mb (bit of a guess these, don't own a D700). The 34.5M numbers you are seeing are likely for a psd version (photoshop native file format) or a tiff version.

A number of other things can affect file size too which happen during shooting, high ISO will increase file size as will scenes with lots of varying tones/hues etc. Also the compression settings you set on the camera will have an impact (12 bit, 14 bit - lossless compression etc).

Generally I wouldn't get too hung up on file size per se. If the quality of the final jpeg (assuming that is the end point of the process) is what you desire then all is good. fwiw, when I save from PS I rarely save at quality 12 as I can see no difference between that and quality of 10, yet the file size is often quite a lot smaller.
 
PaulButler said:
File size is determined by file type and compression. For the same image, saved as a jpeg it can vary by a significant amount depending on the quality (compression) setting. The lower the quality the smaller the file size. I'm guessing the 5.1M you are seeing is for a jpeg. If you have shot the image in raw (a .nef file for Nikon) then the file size on disk will be larger than a jpeg typically between 11Mb and around 18Mb (bit of a guess these, don't own a D700). The 34.5M numbers you are seeing are likely for a psd version (photoshop native file format) or a tiff version.

A number of other things can affect file size too which happen during shooting, high ISO will increase file size as will scenes with lots of varying tones/hues etc. Also the compression settings you set on the camera will have an impact (12 bit, 14 bit - lossless compression etc).

Generally I wouldn't get too hung up on file size per se. If the quality of the final jpeg (assuming that is the end point of the process) is what you desire then all is good. fwiw, when I save from PS I rarely save at quality 12 as I can see no difference between that and quality of 10, yet the file size is often quite a lot smaller.
Click to expand...

Thanks for that Paul - that makes sense - Photoshop is showing the size of the PSD, not the jpeg!

I will take a look at saving at '10' too - save some space!
 
Lyndsey said:
Thanks for that Paul - that makes sense - Photoshop is showing the size of the PSD, not the jpeg!

I will take a look at saving at '10' too - save some space!
Click to expand...
Worth checking that you can't see any difference before settling on 10 :). Also for completeness I never save to jpeg if I am intending to work on it again, multiple saves to jpeg degrades IQ in my experience (in PS I either use PSD or TIFF) .
 
PaulButler said:
Worth checking that you can't see any difference before settling on 10 :). Also for completeness I never save to jpeg if I am intending to work on it again, multiple saves to jpeg degrades IQ in my experience (in PS I either use PSD or TIFF) .
Click to expand...

Thanks again Paul - I generally do all the edits I'm going to in one go, simple stuff - but will take your advice for anything needing multiple visits!
 
I'd ignore most of the above as confusing guff (apart from not needing to save as '12').

The image size that you can see at the bottom is the uncompressed file size. It can be in any format.

The file size shown on disk is the compressed file.

You won't ever see a NEF file in Photoshop because it can't edit Raw images. They have to be converted before hand.
 
DemiLion said:
I'd ignore most of the above as confusing guff (apart from not needing to save as '12').

The image size that you can see at the bottom is the uncompressed file size. It can be in any format.

The file size shown on disk is the compressed file.

You won't ever see a NEF file in Photoshop because it can't edit Raw images. They have to be converted before hand.
Click to expand...

Thanks for your reply Mark!

The reason for my question relates to the other thread I have started today...

I have been looking into the possibility of submitting some of my photos to a stock site. On reading their FAQs their preferred image size is in the region of 40 - 50 megabytes... That's approx 10x the size of my saved images!!! If you have any experience of stock submissions, do they usually require non-compressed files, e.g. TIF?
 
They're quoting the uncompressed size. A full res jpeg of 4000+ px saved at the highest quality should easily give you that.
 
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