Does an image hold more megepixels based on th subject or setting?
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Tringa
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It is not that the number of megapixels changes, eg my camera's sensor has 16 megapixels and that does not change, but the size of the file in meagabytes can vary. Just had a look at a few shots of my shots. They vary in size between 18.7megabytes and 23.9.
I don't know the reason but I assumed that if a shot contains say 5,000 completely black pixels, when the file is store each is not recorded separately but somehow the PC records the value of one pixel and that there are 5000 of them and their position.
This is just a guess, however.
Dave
I don't know the reason but I assumed that if a shot contains say 5,000 completely black pixels, when the file is store each is not recorded separately but somehow the PC records the value of one pixel and that there are 5000 of them and their position.
This is just a guess, however.
Dave
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I believe this is pretty much it, I know that for myself a starscape where you have a large area that's pretty much the same colour or areas of the same colour within a larger area of pretty much the same small range of tones will always be a smaller file size that say a really colourful bunch of flowers where there a massive amount of data in the form of colour and detail to be recorded
An easy demonstration of this should be to take a photo with the lens cap on and one without your blank frame should be a much smaller file
Another example say your shooting in JPEG if you change to B&W the same photo in colour would be larger in colour than in B&W if only marginally some of the time
Matt
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Well if you've large areas completely out of focus you likely also large areas of the same or similar colours
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As a demonstration look how the fully OOF areas of this photo basically merge into large areas of the same/very similar colour
Something Sweet by mwhcvt, on Flickr
Something Sweet by mwhcvt, on Flickr
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Lenses are sharpest at a particular f-stop - normally 1-2 stops down on their widest. When photos are taken at that f-stop, you will have more detail in the image. It is the detail which causes the extra file size as it is more difficult to compress the data (JPEG is lossy compression, raw is lossless compression) efficiently whilst still retaining fidelity. I wouldn't expect it to be much as a percentage of the overall file size though.
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Yeah... that too
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There's also noise. The jpeg compression can't tell the difference between fine detail and high ISO noise, so if you've got the noise reduction low or turned off in your camera noisy images will turn into surprisingly large files.
Think of jpeg compression as a paint-by-numbers chart with instructions. Obviously the more detail (or noise) in the image the complicated the chart and instructions.
On the other hand if you shoot only RAW you'll get the same size of image files all the time.
Most cameras will tell you how many more images with the current camera settings you ought to be able to fit on the memory card.
Think of jpeg compression as a paint-by-numbers chart with instructions. Obviously the more detail (or noise) in the image the complicated the chart and instructions.
On the other hand if you shoot only RAW you'll get the same size of image files all the time.
Most cameras will tell you how many more images with the current camera settings you ought to be able to fit on the memory card.
MWHCVT
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Sorry but that's just wrong, shooting RAW will not give you the same file size all the time at all
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It will unless you're shooting compressed RAW. Admittedly some cameras don't let you choose uncompressed RAW, although some of those (like my Sony A77) use a RAW compression method whose file sizes vary very little (maybe 5%) compared to the huge variation (around 250% using the same camera settings, even more if I change the settings) in jpeg file size.
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I shoot uncompressed raw file sizes do vary.
MWHCVT
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You can shoot on some cameras reduced resolution size RAW I can do that on my 5D3 but it's not a compressed file in the slightest the is as far as I'm away no such thing as a compressed RAW...but even these reduced resolution will still feature wide variance in file size depending on the detail captured...
I can have RAW files for full size/resolution RAWs that vary from about 22mb right up to 38mb is about the largest file I remember...I think maybe you are confusing file size and resolution...but even reduced resolution is not compressed, compression would me loss of actual data....but no data has been lost as it didn't exist in the first place when shooting at a lower resolution
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Perhaps I'm misunderstanding your post. But you can definitely get both lossless-compressed and uncompressed RAW files in Nikon cameras.
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depending on the content of the scene (including noise etc) depends on how efficently a compression algorithim can run. So a large area of black will compress more effectivley then a very noicsy street scene (noise is random, so compression doesn't work as well on noisey images). Depending on the compression options selected (RAW can be compressed of\r uncompressed) and we know JPEG is a compressed format then the content affects file size that way
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Thats because noise is random, so the algorithims can't compress it, so you get bigger files at high iso
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Just in passing:
Sony raw files are lossy compressed. I think that this applies across the board.
Nikon raw files can be - and one paper I turned up suggests that any loss is mainly in the highlights.
Canon - so far as I could see - only do lossless compression on raw files.
All the answers above as to how settings and subject affect the amount of possible compression seem to be complete - I can't think of any others off the top of my head.
Sony raw files are lossy compressed. I think that this applies across the board.
Nikon raw files can be - and one paper I turned up suggests that any loss is mainly in the highlights.
Canon - so far as I could see - only do lossless compression on raw files.
All the answers above as to how settings and subject affect the amount of possible compression seem to be complete - I can't think of any others off the top of my head.
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A completely uncompressed image takes up a huge amount of space, it's dictated solely by the dimensions of the image. You can see this in action if you use Photoshop, start a new image and you can see the Image size to the right, changing the dimensions causes that figure to change accordingly.
When you take a shot on your camera the file it produces is compressed, it may use a compression method which doesn't reduce any detail (lossless) but the important part is it's being compressed so the more complex the scene the larger the file size.
When you take a shot on your camera the file it produces is compressed, it may use a compression method which doesn't reduce any detail (lossless) but the important part is it's being compressed so the more complex the scene the larger the file size.
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I didn't know that I know that Nikons do also do TIFF files as well as RAW but I wasn't aware that either was a compressed format, just that one is a higher (bitt space) not sure I'm using the right phrase there to be honest
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Nikon do uncompressed & compressed lossless raw in both 14 & 12 bit. They do TIFF as well if you really want that file size.
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Really didn't know that, but then I'm a canon shooter so don't tend to spend a lot of time learning about Nikon kit...I'll be honest I don't really see the need for so many variations in the type of file you can shoot
Canon RAW files are always compressed, but the compression is lossless (like a zip file, once you decompress it then you have exactly the same data you started with). If it wasn't compressed then file sizes could never vary, they'd always be exactly the same. I think you're confusing compression with lossy compression, such as with a JPEG file.