File size, dpi and printing

[Goody13]

I wonder whether someone would be able to help with a question on file size and image printing, which may be up to A3 size. I am entering a competition where wining photos will be included in a calendar. All photos I will enter have been either scanned or converted from RAW at 300dpi. My smallest file size (from a scan of a 6x4 print) is around 850KB. My RAW conversions to JPEG tend to be between 4-6MB, depending on how much editing I have done and the compression/quality setting used (I edit and convert in DPP).

The guidelines from the printers for entry are as follows:

A note regarding the sizes of high res images:

For your picture to be large enough to be a contender for the cover of the calendar (a cover image would need to be 300dpi at A3) the file size needs to be around 7-10MB.

(However, photos for use inside the calendar only we can get away with 300dpi at A4 a file size 3-5MB so if you have any great photos at that size – please send them in!)

Therefore it is probably best to aim for the larger file size of 7-10MB.

Has the printer got this correct, or am I right in thinking that just dpi is the crucial issue for printing? Does my 850KB picture at 300dpi instantly need to be ruled out?

I do not have much knowledge of printing in large sizes, as is probably clear from the above, so any guidance/advice would be appreciated, especially if I can demonstrate to the printer that I do not need a 7-10MB file.

 

[Nod]

Off the top of my head, A3 is 420mm x 297mm so 16.54" x 11,7" which at 300dpi would be around 17.5 MP. Depending on the compression, the file sizes quoted seem about right for highest quality JPEGs. TBH, you'll need to upscale 450D images to get 300dpi @ A3 but it can be done.

I fully agree that what they're asking for is probably excessive but if that's what they say they need, that's what they'll expect to receive as entries. I've recently had some panoramas from a Fuji XF-1 printed 24" wide and they look fabulous and the printer for those wanted 240dpi images. I've home printed shots from an old D70 Nikon at A3 and again, they look great, as do the ones that replaced them on the wall - more XF-1 shots.

Good luck in the competition, whichever categories you end up being eligible for.

 

[Goody13]

Thanks, John. It's a calendar competition for a work calendar, so the printer's requirements could be up for debate if they are wrong! I suspect that a lot of people wanting to have compact shots used will be ruled out on file size when they may have perfectly good shots otherwise that would print acceptably.

I have checked the size of my smallest possible entry (the scan) and it is actually 1.8MB, but was about 900 before editing, so that's where I think file size is a bit a a red herring, as nothing has been added to the original picture other than a bit of sharpening and colour balance change.

So, if I had a 5MB picture at 300dpi that may be too small for the cover, I could do a bit of editing, the fle size would increase to, say, 7MB, and instantly it would be eligible!

How is that sensible ... ?

 

[Nod]

It's not is the quick answer - file size is fairly irrelevant. A JPEG from a D800 could well have a file size smaller than a raw from a 450D but the pixel count (resolution) of the former will be far greater.

The effective ruling out of shots from compacts could be in your favour and clear the field for the entrants who (maybe) take their photography a bit more seriously. Having said that, most modern compacts will probably have higher pixel counts than your 450D (but probably lower image quality).

Were I in your shoes (and if it's possible) I would rescan at a resolution high enough to meet the printer's specified needs. They're making the rules and you're aware of them so it would be a shame to miss out due to a technicality! I would be tempted to pay them a friendly visit to ask if they really mean large files in terms of MB or large files in terms of MP - there's a big difference!

Now for the John bit... My real name (or at least the one I'm most known by!) is actually Nod, the John Prescott comes from my wife's an my choice of car - we're fortunate enough to both drive Jags like the huge(ly missed) former deputy PM and slugger John Prescott (although ours are actually ours rather than the taxpayers' or the banks'!) and is the management's idea of a joke (and an old one at that!!!)

Again, good luck in the competition.

 

[Goody13]

Thanks, Nod. I did think it strange that there was a John Prescott on here, but not beyond the realms of possibility! Maybe I should rescan the photo as a TIFF!

 

[Nod]

That will certainly up the file size (and is also handy if you want/need to do multi session PP on the result - multiple save/open cycles on JPEGs can [and will] degrade the image but AFAIK, TIFFs don't suffer in the same way.)