Why 5DmkII file size varies so much....?

[jrda2]

When shooting my 5Dmkii in JPEG (all in "L" fine quality) I have noticed that the file size of each picture is commonly around 5.3-6.2 MB - just as indicated in the Canon instruction manual. However, many times the file size will go up to 7-12 MBs without changing any settings on the camera. Sometimes the file size changes with a lens change, but I have also noted wide variations in file size using the same lens and same settings with the only change being the subject. I am curious why there is such a variance in file size without changing settings?

 

[timkbryant]

It might have to do with what is in the frame. I've noticed that when I take photos, if there's a difference in detail, the file size changes even if the settings don't.

 

[tt]

Likely varying amounts of compression dependent on what's being shot.
Eg of the picture was completely blown out or completely dark - the value of each pixel could be white or black.
That should compress very well.
Should be able to test this out - take a picture with te lens cap on and note the size vs normal.

 

[Admin US West]

The amount of noise and detail varies from image to image. A 5D MK II image should be around 25mp, if you are shooting Raw, but the size will vary a lot.

Turn up the ISO to 3200 and compare image sizes with lower ISO shots. The noise is visible as a very fine detail. Compare a shot with few fine details with one with many small details, and you will see what happens.

 

[5dmk.iii]

Depends on the details. (especially fine details.)

Sharp (or even oversharp) images are larger than soft images. (try it, take a shot, and then over sharp it)
Colors add to size
Bit depth adds to size


Then there are format specific things like fine/med/low settings AKA compression levels.

 

[Brendon]

Check out wikipedia and the JPEG section. http://en.wikipedia.org/wiki/JPEG#JPEG_compression you will get your math fill for a month! Short story is that sharp and high contrast edges require a lot more space to render.

As a test, take a picture of a blank wall and another of a house plant. The second should be much larger. The more detail that is saved in the pic, the larger the file.

Exposure will also change the file size as parts of the image may blow out or be clipped in the dark regions and decrease the amount of overall detail in the image.

 

[PaperTiger]

All of this is true. It became especially apparent when I was exporting all the image samples for my website and had to keep them very small (<200 kb for fast load times) and you'd really have to work with your compression settings for certain images. A b+w image with a lot of white or black space is going to be considerably smaller than a colour image with loads of fine detail. You'll see this variance in RAW files as well, although it's often not as drastic.