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General photography questions and answers: Discuss Uncompressed file size advice...I have been looking at various stockwebsite to try my hand at, one i have seen is Alamy. One of ...
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Old 25-05-2009, 10:40   #1 (permalink)
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Uncompressed file size advice

I have been looking at various stockwebsite to try my hand at, one i have seen is Alamy. One of the Criteria is the file should be a uncompressed file of more than 48mb in jpeg.

Ive been shooting in RAW with my Alpha350 using Capture One to convert to 8bit tiff, this gets me an image at around 40mb, but when i use paint shop pro to convert to jpeg, the maximum size i seems to be able to manage is half the size.

The question being is there something i am missing in the settings which would give me a larger image, or is the software i am using i.e paint shop pro not capable of converting images to higher jpeg format?
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Old 25-05-2009, 11:12   #2 (permalink)
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Re: Uncompressed file size advice

The problem with Raw files is that for this file there is not one single format of Raw file.Nikon is different to Canon and Sony and so on.
The problem with the world is that it develops a standard to which everyone can alter that standard so that there is no real standard.Great isn't it?

I thought that any jpeg however large ,will have some sort of compression otherwise the use of jpeg would not have a lot going for it.

You could convert your file to TIFF as I think this would be accepted for your needs .
Regards .I hope this helps.Brian
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Old 25-05-2009, 11:22   #3 (permalink)
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Re: Uncompressed file size advice

Regarding JPEGs and RAW files, there's a difference between compression and lossless compression. ZIP files and most RAW files are compressed, but losslessly so all data is retained. (That's why RAW files from the same camera are different sizes.)

JPEGs are compressed but usually they are lossy to a greater or lesser extent depending on the degree of compression. You can have lossless JPEGs.

TIFFs are usually uncompressed (unless you use LZW compression). The file size is directly related to the number of pixels in the image, and the number of bits per pixel. If Alamy want a file size >48MB (and heaven knows why!) then you could submit a 16-bit TIFF.

An "uncompressed file of more than 48MB in JPEG" doesn't really make sense, as all JPEGs are compressed and you would struggle to achieve a file of that size with most cameras.
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Old 25-05-2009, 11:24   #4 (permalink)
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Re: Uncompressed file size advice

Brian thanks for the reply....... From my Capture One software, i do convert to Tiff, this gives me an imgae size of 40mb, the problem i seem to be having is when i convert to jpeg, the maximum size i can manage is around 15mb. Will check with the specification Alamy require to see if sending images in Tiff format is acceptable.
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Old 25-05-2009, 11:35   #5 (permalink)
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Re: Uncompressed file size advice

Quote:
An "uncompressed file of more than 48MB in JPEG" doesn't really make sense, as all JPEGs are compressed and you would struggle to achieve a file of that size with most cameras.
I have a feeling that i may have interpreted the specification for Alamy incorrectly then as they state;

Quote:
Uncompressed file sizes of more than 48MB, we recommend that you do not interpolate your files to more than 55MB. This means you should make your JPEG file from an 8 bit TIFF file that is at least 48MB. If you have a camera that is capable of producing an uncompressed 8 bit, TIFF file size of over 48MB then leave it that size.
I take it from reading this, and following my failed endeavours with editing to try and get a jpeg image at 40+mb; That as long as i convert to jpeg from a 48mb TIFF file, this would be acceptable?
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Old 25-05-2009, 12:06   #6 (permalink)
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Re: Uncompressed file size advice

remember not to confuse file sizes with size in memory (bitmap).

<width> * <height> * <bit depth>

The size of the file and format used is irrelevant in this calculation.

a 6mp camera produces (uncropped) a size of: -
45MB @ 8bit
91MB @ 16bit

Double those for a 12mp sensor.


Why they don't simply specify minimum sizes and file formats I don't know, but I guess they need to make is suitably complicated.
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Old 27-05-2009, 09:32   #7 (permalink)
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Re: Uncompressed file size advice

I don't submit to any photo sites, but I read your post with interest and something didn't add up. File size of 48mb - surely not, that would be huge and wouldn't you lose quality getting it that big?

Anyway, I had a quick look on Alamy 's forum and below is from the horses mouth (a sticky from their forum admin) and hopefully answers your question.


Our required file size for submitting Jpegs seems to cause an incomprehensible amount of confusion with a high volume of photographers. Put simply, we are flabbergasted as to how many times we are asked, daily, of what format and size of images we require!

Let’s set the record straight right now. First and foremost, yes, we want you to send Jpegs. No, we don’t want you to send Tiffs.

The reason for this is that we provide our clients with Jpegs to download, not Tiffs. It’s been industry standard to work like this for a long time now and even in the days when we required you to send us Tiffs, we converted them to Jpeg for the clients. Yes we know Jpeg is a lossy format, but to the naked eye, there is no visible difference between a high quality Jpeg and a Tiff file. The client can simply download the Jpeg, save it as a Tiff, and work away on it saving as many times as they like without loss in quality. It’s really that simple!

Now that’s out of the way let’s move onto file size. Jpeg is a compressed file format. The compressed file size (size on disk) varies with picture content and should generally be ignored, as long as it’s no bigger than 25MB, which is our upper limit for Jpeg size. What’s important is the uncompressed (opened) file size. The opened file must be at least 48MB at 8 bit to get through our quality control. Typically a 48MB 8 bit Tiff file will be between 3MB and 15MB as a Jpeg if your image was shot digitally. Film scans will be larger. This is because Jpeg “sees” film grain as image detail and compresses it too. Remember, we do not want a Jpeg 48MB in size as that would be ridiculously large when uncompressed (opened)!

One thing you don’t want to do is work on your images whilst they are in Jpeg form, repeatedly saving as you go along. Saving a Jpeg as a Jpeg is pretty much a no no, as you are recompressing an already compressed file.

Now there are various ways of doing this, but an ideal workflow example for creating the required file size would be:

* Convert your image into a 8 bit Tiff file (save as, Tiff)

* In an image editing program such as Photoshop, upsize the image to a minimum of 48MB. (If you make your longest side 5200 pixels and keep it in proportion to the shortest size, this should give you a file size of just over 50MB)

* Make any alterations as needed, inspect the image carefully at 100%

* At the very last step save your image as a Jpeg and send us that Jpeg. Remember, the Jpeg is the compressed size so this will typically be between 3MB-15MB

There are a handful of digital cameras on the market that produce native uncompressed file sizes above 48MB so you will not need to do the above for those. The same goes for film scans.
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Old 28-05-2009, 08:23   #8 (permalink)
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Re: Uncompressed file size advice

Rodriguez, thanks for this, its a pity that they couldnt put a simple line in like
Quote:
Typically a 48MB 8 bit Tiff file will be between 3MB and 15MB as a Jpeg if your image was shot digitally.
in thier opening standard specification on the website, especially as they have clearly stated they keep getting asked the same question about submitted file size. At least i know that the software i have will be able to convert the appropriate photos i take in the future. Many Thanks
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Old 29-05-2009, 02:30   #9 (permalink)
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Re: Uncompressed file size advice

Not quite correct. Alamy want a very large image. The uncompressed JPEG simply means with them that when you open your JPEG file in Photoshop that it is 48MB in size. The disc space used will only be between 3-15MB. If you look in PS as the file is "opened" it is uncompressed to 48mb.

You'll need a larger camera than 6 mega pixel camera (APS sensor) to get a 48mb 8bit file without interpollating it on a APS sized sensor. I have to enlarge my 15.1 sensor images to get them that big. Look at the pixel length they want of 5200 for an indication of the actual image size required.
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