Alamy, in common with many other traditional stock photography agencies, have a minimum file size requirement for submissions. In Alamy’s case this is a 48mb uncompressed file size at 8 bit but it is often 50mb at other agencies. As Alamy is non-exclusive you may sometimes be submitting the same images elsewhere so it makes sense to upsize to 50mb. Where this size came from I’m not entirely sure but I was told once it is because it allows cropping of a horizontal image for use on an A4 vertical page. Whether that is true or not is really academic, 48mb minimum is the rule, and if you don’t play by the rules your images will be rejected!

So, depending on the resolution of the camera you’ve shot with there is likely to be some resizing of your image, i.e. interpolation, required to meet this standard. This sounds simple enough but does cause a lot of confusion for many new contributors. Hopefully this article will help to clear up some misunderstandings and help with preparing images for Alamy submission.

Firstly, Alamy have a comprehensive guide for contributors which anyone submitting, or thinking of submitting to Alamy should obviously read through. I’m not going to reinvent the wheel here, but hopefully add a spoke or two and maybe oil the chain to help your submissions sail through QC smoothly.

The quick guide

1. Resize your longest side to 5120 pixels
2. Ensure resolution is set at 300 pixels/inch
3. Ensure constrain proportions is selected
4. Use Bicubic or bicubic smoother method
5. Save your file as JPEG at between 10-12 quality

The nity gritty

Remember Alamy now only want JPEG files, so what you upload won’t be a 50mb file because JPEG is a lossy file format meaning the file has been compressed. What this means in practice is your upsized file will usually be between 3 – 10mb depending on the subject matter and detail in the image.

How you get this file can vary depending on your original image size, format and the software you’re using. If you’ve shot a RAW file your RAW software will have an option to resize the image before you open it for any further tweaking in an image editing application or save it as a JPEG.

Alternatively you can leave the resizing to be done in Photoshop or whatever editing software you are using. If you have photoshop 7 or above or an equivalent this is perfectly adequate for interpolating your images. Prior to this it was recommended to use specialist applications or plugins such as Genuine Fractals. While I’m sure these still do a great job, you don’t need them now. Another old piece of advice you’ll still stumble across is the idea of step, or stair, interpolation. This basically involved resizing your image in a series of mind numbing increments until you reached the required size. You don’t need to do this anymore, if indeed it ever added any advantage. Trust me, you don’t need the extra excitement; you have keywording for that.

Now some points to keep in mind are that you are aiming to finish with an 8 bit JPEG file that would have an uncompressed image size of 48 – 55mb. However JPEGs are compressed; so your file will not actually be this large. This is a good thing and the whole advantage of using JPEG as a file format. Uploading batches of 48mb+ files would be painful. If you were to save this file as TIFF however you would have it in its uncompressed size; which is what stock agencies expect their clients will do once they have your image.

JPEG as a file format offers huge advantages for file transmission between creators, agencies and clients. However it is not the ideal format for actually working on images. Each time a JPEG is saved it effectively dies a little. Listen carefully and you can hear the scream under the hum of your hard drive every time you save. Ideally you work on your file as a RAW and/or TIFF and then save a JPEG version when finished for uploading. This JPEG is then sent to any purchaser who, hopefully, immediately makes a TIFF out of it and works on that. In the real world of course that doesn’t always happen, but you should never do more than minor tweaks and one save on a JPEG or you’re asking for trouble when interpolation has been thrown into the mix too.

The caveats

Interpolation inherently asks for trouble. To be honest I’m quite amazed how good a job it does. Despite this never forget you’re effectively conjuring more from less. In essence you need a high quality starting point; if your original image in its native resolution isn’t quite up to scratch interpolating it is only going to make matters worse. You can only push things so far. Alamy state a minimum of a 6mp DSLR and I can personally vouch for D70s images managing the stretch, however having more resolution makes the task more reliable.

I hope that is of some help and wish you luck with your Alamy upoads!