Extra shots with lower ISO?

petersmart

petersmart

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I went out today determined to follow my own advice about taking greater care with shots.

I also wanted to increase my Neat Image profiles.

Because of this I set the ISO to 400 and after taking a number of shots noticed something REALLY odd!

I have a 16Gb card in my 450D which normally gives me 869 shots at 1600 ISO.

Today however the indicator showed a much greater number of shots when shooting at 400 ISO.

When I investigated the indicator on the 450D tells me that when I shoot at 100 ISO I should get 1022 shots going down to 868 shots at 1600 ISO.

Here is the complete list at all ISOs:

1600 - 868
800 - 922
400 - 966
200 - 999
100 - 1022

It appears from this that using lower ISO should give you more pics - has anyone else noticed this?
 
Yes, this is normal, if you're shooting JPEG, or if your camera stores RAW files in any compressed format.

Higher ISO means more digital noise, which is random and therefore can't be compressed as well by the JPEG or other algorithms. So the files end up larger and you get fewer of them on a card. Conversely, lower ISO -> less noise -> easier to compress -> smaller files -> more photos on card.
 
StewartR said:
Yes, this is normal, if you're shooting JPEG, or if your camera stores RAW files in any compressed format.

Higher ISO means more digital noise, which is random and therefore can't be compressed as well by the JPEG or other algorithms. So the files end up larger and you get fewer of them on a card. Conversely, lower ISO -> less noise -> easier to compress -> smaller files -> more photos on card.
Click to expand...

No I was shooting full size RAW - I never shoot anything else.
 
Yeah. My cameras do the same, all of them do I think...

But...this is just the camera guessing and as you take pictures the shots remaining number will change and adjust itself accordingly.

I've never filled the memory card to check how accurate the camera can guess but there's little point as during normal shooting you can expect the file size to vary depending upon the composition and content. Overall I think that it's best to view the shots remaining number the camera display as being just a rough guide.
 
woof woof said:
Yeah. My cameras do the same, all of them do I think...

But...this is just the camera guessing and as you take pictures the shots remaining number will change and adjust itself accordingly.

I've never filled the memory card to check how accurate the camera can guess but there's little point as during normal shooting you can expect the file size to vary depending upon the composition and content. Overall I think that it's best to view the shots remaining number the camera display as being just a rough guide.
Click to expand...

I definitely do and it's very unlikely I would ever fill the card up - the most I've taken on any one day is about 500 (an my 350D) - It's just something I've never noticed before.

However in full RAW I think the file size is fixed - I know that using a 2Gb card in the 450D the file indicator was spot on, so I've no reason to believe the numbers to be inaccurate.
 
If you had 2 images the same but one was B&W the B&W one would be smaller in KB size so i guess that the higher ISO means more coloured pixels for the computer to process?
 
I don't think that the RAW file is a fixed size, mine seem to be all over the place.
 
Well it just got weirder!

I've just checked the RAW file sizes from my 450D which are supposed to be 12Mp and all of them are larger with some as high as 20Mb!

What on earth is going on?

EDIT: OOPS - think I see the prob - 12 Mp is NOT 12 Mb!
 
Yup. Easy mistake to make. I think that they do vary in size though.
 
woof woof said:
Yup. Easy mistake to make. I think that they do vary in size though.
Click to expand...

Yep I just checked the Canon specs:

(File Size) RAW : Approx. 15.3 MB (4272 x 2848 pixels)

Well that explains that - hopefully!

The odd thing is that when I use DPP to turn them into TIFF files the TIFF files are always the same size - I think 72Mb.
 
RAW file sizes are not fixed. Most RAW formats employ lossless compression and sizes will be increased by unpredictable image content, sepecially noise. On my 7D RAW images can be 3 or 4 times larger than average for high-ISO shots.
 
Some of the biggest shots I've ever taken baffled me. They were taken on a misty day and there were no features visible in the sky at all, it was just featureless and grey. I thought that the files would be small (no detail there...) but they were huge...So I asked why on a forum and I was told that the scene wasn't as featureless as I thought and that my camera was actually trying to reproduce the water droplets in the mist.
 
woof woof said:
Some of the biggest shots I've ever taken baffled me. They were taken on a misty day and there were no features visible in the sky at all, it was just featureless and grey. I thought that the files would be small (no detail there...) but they were huge...So I asked why on a forum and I was told that the scene wasn't as featureless as I thought and that my camera was actually trying to reproduce the water droplets in the mist.
Click to expand...

I find that rather hard to believe - I don't think any sensor would even see the water droplets - more likely the different shades of grey within the mist would make a larger file.
 
Maybe they were pulling the new guys leg???? :razz::lol:

For whatever reason those featureless shots produced big RAW files.
 
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