Printing resolutions A4/A3?

[Tobyh]

All,

Probably like many here I take loads of pictures but don't print many. I've now been asked if I would like to display some of my images at work and am looking at how to get the best quality.

I've decided that my A4 printer, although good, is just such a pain to get it to print how I am seeing the colours etc that I'm going to send them off to be printed. It'll probably end up cheaper and alot less hassle in the long run.

So my questions are -

I have a site in mind but if anyone has any positive experiences with online printing companys i'd love to hear - I guess a PM as no advertising is permitted here.

What resolution image do you submit for say an A4 print. I'm wondering what will happen re sharpness when it gets resized - is that taken into account at repro stage?

Has anyone had any printed out for the purpose of selling them, eg A4 print, with a card frame and sealed bag - how did that work out?

I'm sure you can see how my mind is working and I'd love to hear from anyone with advice.

Thanks in advance

TobyH

[nigel_b]

I've had loads done at Asda, 10x8, £1.20, one hour service but usually ready in 20 minutes or so. Walk in, upload, walk away, simple. I don't know if they do A4.

[DivingDave1980]

Hi!

I've used an online shop before - ds colour labs (don't think that breaches the forum rules as it isn't spam or advertising for financial gain). I ended up asking what output resolution they support and they replied very quickly that it is 300 dpi. That is usually the best print quality that you'll ever require so you might as well go for that. When I used them I resized the images myself and uploaded them, and they were printed and sent to me in a couple of days.

For resizing, if you want a resolution of 300 dpi then you need to multiply your length (in inches) by 300 and your width (in inches) by 300. For A4 (8.3 x 11.7 inches) this equates to (8.3 x 300) x (11.7 x 300) which is 2490 x 3510 which is the equivalent of 8.7 megapixels.

If your camera doesn't support this resolution then 200 dpi would probably be more than acceptable (unless you got your loupe out!) which would be 1660 x 2340 and this equates to 3.9 megapixels.

Hope this helps (and maybe stimulates some discussion about what people think is a good resolution). I would search for online printers and ask a few of them their output resolutions and see what they come back with, but I would certainly recommend ds colour labs. Although I've only used them once (in fact I've only used online printers once) but they were very good when I did and would use them again.

Dave.

[Tobyh]

Dave,

It does indeed help, thanks. It makes me realise that the resolution I had in mind is way to small for the quality I hope to achieve - just as well I find out now before I process too many

I have been wondering how the quality of the image you submit translates into print when it is "resized". By this I mean...if I left a full 12mp shot at original size it doesn't necessarily look fantastic and as everyone knows, the smaller the image is made, the better it looks. Hope that makes sense. With a digital image this of course means that if you sharpen for a certain size and then make the image smaller it will soften slightly. How does that work in the print process?

Hope that makes sense. Welcome a discussion on this

TobyH

[Geoff F]

Best printing resolution does partially depend on the type of paper, but yes as Dave said 200 to 300 should work well.

I print my own photos and generally don't worry too much as long as they are at least 200 ppi. The actual printer settings (dots per inch) are normally more important than having exact photo resolution.

Having said that, I always consider the image ppi when resizing photos. And this is where it can appear complicated; although it is actually quite easy as long as you don't panic!

Some editing programmes import photos from the camera at 72 ppi which gives you a massive apparent image size, but needs to be resized before printing, although this often happens automatically.

Files from my converted Raw photos are imported at 300 ppi with my current software. But when I tried the latest version of that programme I found it was auto resizing these photos to 96 ppi and although there wasn't any data lost because the photo dimensions were increased, it was tending to confuse me so I returned to the earlier programme.

Once that the maths are clear though, as Dave clearly explained, everything should be straightforward.

When resizing downwards, I don't see any point in needlessly throwing away good pixels so I usually tend to let the ppi increase as the dimensions decrease. But, again as Dave mentioned, there is little to be gained by going beyond 300 ppi.

However, when massively resizing downwards (eg for internet sizes) I have to have a 'colossal pixel sale' and discard far too many for my liking. This often produces a soft poorly saturated image which requires a bit of tweaking.

Likewise, when increasing in size there is often a bit of balancing between accepting a lower resolution in ppi or just adding extra pixels to get the image dimensions/resolution correct.

The risk with adding pixels is that these 'new' pixels have to take their details, like colour, from their neighbours so there is always a potential risk of some loss of quality during any substantial upward resizing.

But in most cases, modern software does cope well with this problem and it usually isn't noticeable. Although it is always wise to use the best quality options (eg Bicubic Interpolation) when making considerable variations in image size, in either direction.

Most printing companies tend to ask for 300 ppi but unless this is coupled with image dimensions (eg A4 at 300 ppi) this requirement can become meaningless. I suspect this is chiefly to prevent someone sending in a photo which has been resized to exact dimensions but with a low resolution (eg A4 at 72 ppi) which wouldn't print satisfactorily.

Basically though, unless I am doing a massive resize, I just try to keep my pixel numbers reasonably similar to the original and let the resolution vary between 200 and 300 ppi as suits.

The worst trouble that I find with the image size/resolution dilemma is trying to explain it. I am perfectly happy with the idea in my mind - but attempting to explain it coherently to another person is quite different!

You might find this useful http://www.cambridgeincolour.com/tut...mera-pixel.htm

and this http://www.cambridgeincolour.com/tut...erpolation.htm

There are quite a few other tutorials there that you might also find beneficial.

[DivingDave1980]

I started writing a reply and noticed Geoff has got there before me with a much better explanation!

I believe, though, that ds colour labs only print at 300 dpi so if you use them then I would do that (and also make sure the colour space you are working with is sRGB).

Dave.

[Tobyh]

Geoff,

Thanks, excellent stuff, it's all got me thinking

I import my images into Elements using Camera RAW. I use a D300 so it's a 12mp image. When I look at my options in Camera RAW it appears to be saying to create all new images at 300ppi whereas when I finish tweaking and open them in elements they have clearly been changed to 240ppi. I'm wondering whats happening here? Are they meant to be 300ppi and if i resize once they hit elements I am just putting them back to their original state?....or ....are they being resized, losing some info and then i'm resizing again and it's having it's best guess at the "extra" pixels?

Thanks in advance

TobyH

[DivingDave1980]

Hi Toby,

The number of pixels per inch only affects how the image is printed. If you have an image at 3000x2500 which is 300 ppi, then the same image at 70ppi (or any other ppi) will still be 3000x2500 and therefore have the same number of pixels and therefore the same information will be contained within it.

If you were to print out both images, the 300 ppi image would be 10 x 8.3 inches whereas the 70ppi image would be 42.9 x 35.7 inches but each inch square would contain less "squares" which make up the image (90,000 in the 300ppi image and 4,900 in the 70 ppi image).

The point of this is that you can change the ppi without affecting the image quality, but if you re-size the image (from 3000x2500 to something else) the re-sizing algorithm you use will affect the image quality (to a certain extent which you may not notice).

Dave.

[Tobyh]

Dave,

Thanks very much. Think I'm finally getting it!

[Geoff F]

I don't use your editing software, Toby, but 240 ppi may be the default import setting for that programme. In which case it would automatically increase the overall image dimensions to fit the new resolution.

If you want to then export at 300 ppi be careful to check that you don't alter the total pixel numbers when resizing, the dimensions should then decrease slightly. I think you have to click or unclick a box somewhere before entering the new numbers. My software works in a similar fashion, although slightly differently.

Although, in reality (unless you must have a definite image size or resolution) it might be just as well to accept 240 ppi as the standard default setting. It's only really when software defaults substantially to 72 ppi for example that serious complications could appear for the unwary.