File formats and data compression

wooky

wooky

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Martyn
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At work we're to undertake an exercise on different imaging file formats and compression rates - basically RAW v JPEG at different degrees of compression (we currently use Nikon D300S's and images are currently captured in JPEG format).

The exercise will cover different subject matter such as general shots, article photography, mark photography and this may be extended to to cover injury photography and night time photography.

We're working with certain constraints, these being data storage and network bandwidths to move images around the IT system so smaller file sizes represent an advantage, however this has to be balanced against the need for the imaging product to fulfil its purpose i.e. the images to be useable.

So any thoughts on what would be the most suitable file format to use and compression rate/type to allow us to achieve this.
 
I know that Neil, however the network bandwidth is potentially the biggest problem and most likely one that cannot be changed or improved.
 
I think the jpeg compression will depend on your expectations of the image afterwards. You can considerably reduce the jpeg file size and maintain reasonable detail but you won't get a quality print from it.

I think the best is for you to experiment with different compressions and judge which you can live with as a compromise of your bandwidth.
 
You could do with defining your requirements more thoroughly. For example, what's the workflow for the images? At which points will they traverse the network? At which points of the workflow are you willing to switch to lossy compression? Have you considered reducing image bit depth or resolution? TIF is just one format which can be compressed without loss, but are all devices throughout your workflow able to process them? Have you considered the varying levels of compression available within the likes of JPG?
 
How big are the files allowed to be to keep IT happy? How good (well exposed etc) are the images (are they likely to need rescuing or extensive PP work)? I would think that JPEGs will probably be enough in terms of IQ as long as the shots are 1/2 decent, especially if the cameras are set to Large, Fine to keep artefaction to a minimum at source. Experimentation will show how far you can take compression if/when file size reduction is done in PP. If all the file transfers are to go in under the same roof, consider using a runner to transport USB keys or optical disks between offices if file sizes can't be reduced to IT pleasing dimensions.
 
Images are generally of a reasonable level and require little PP.

The file transfer wouldn't be under the same roof, some would be taking place from a networked machine in Inverness to a server in Glasgow or a server in Dundee for example.
 
wooky said:
Images are generally of a reasonable level and require little PP. The file transfer wouldn't be under the same roof, some would be taking place from a networked machine in Inverness to a server in Glasgow or a server in Dundee for example.
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Leased lines, or adsl link? Need lots more info on infrastructure and what exactly is being achieved please.
 
If you're dealing with an IT department, you should ensure you're singing from the same hymn sheet. Bandwidth and compression both have very specific technical meanings and are used incorrectly in common parlance. You don't want to find you're planning for the wrong thing.

Compression is a reduction in dynamic range and bandwidth is an analogue measurement. They are usually misused to mean data reduction and data rate.

JPEG may be a bad idea in this case as the file size for a given quality setting is nondeterministic, so bursts of highly detailed images could cause delays. Is guaranteed transmission time required?
 
st599 said:
If you're dealing with an IT department, you should ensure you're singing from the same hymn sheet. Bandwidth and compression both have very specific technical meanings and are used incorrectly in common parlance. You don't want to find you're planning for the wrong thing. Compression is a reduction in dynamic range and bandwidth is an analogue measurement. They are usually misused to mean data reduction and data rate. JPEG may be a bad idea in this case as the file size for a given quality setting is nondeterministic, so bursts of highly detailed images could cause delays. Is guaranteed transmission time required?
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Agreed. This is more of a conversation that should be had with the IT dept rather than the Internet anon.
 
Agreed with the above. You should be discussing this with people who know your business, its policies, its workflow and its infrastructure.
 
What are the minimum and maximum images sizes required? Obviously physical image size relating to pixels (etc) and the final output dpi/ppi can affect file size. Or do you need to have images as the actual image size from the camera?...

Are images being controlled by an individual or particular department and the distributed, or do others around the network need access to the original file?

At my old publishing house we'd submit JPEGs to the repro department, they resize for designated use and then the designers knew what they'd be getting. Images were resized to a standard set of sizes, which made file handling a bit easier across the system.
 
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Not withstanding the advice above to engage with your IT dept, a simple means to reducing file size significantly is to switch to black & white (well greyscale). It all rather depends on the purpose of the final images.
 
Furtim said:
Not withstanding the advice above to engage with your IT dept, a simple means to reducing file size significantly is to switch to black & white (well greyscale). It all rather depends on the purpose of the final images.
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Provided you don't use a B&W effects program like DxO. The film grain they add requires significant bits to encode.
 
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