Determining how large you can print when viewing in LR/PS

[zebedoo]

Hello

I am trying to establish 'how big' I can get away with enlarging several images. The images vary, in that some have been radically cropped (and as such are only around 2000 pixels wide) where as others are 'full size' tifs created straight from the RAW file and are nearer 4000 pixels wide in their current form.

I am looking to offer print sizes to clients (ideally) up to 39 x 28", but before I offer such a service I need to make a judgement on the 'maximum' enlargement that individual images can handle. Clearly some will lose significant detail at this size and would benefit from a smaller maximum print size, where as others may well reproduce satisfactorily at a larger size.

I would appreciate any tips and advice re how I can make a judgement when viewing enlarged images in Lightroom and/or PS, as to whether, once printed, they are likely to be 'acceptable'.

Is it just a case of enlarging the image, then viewing at 100% magnification to establish how much detail and sharpness has been lost, or is there another, more effective way. Obviously, sending a load of test prints off would help, but printing at this size is expensive, so this really isn't an option. Unless perhaps I pick an image that is likely to be as 'bad' as they get and see how that copes, on the basis that everything else will likely cope better?

Any help would be appreciated.

Many thanks,

Si

[GeoffWessex]

As the suggested minimum dpi you can get away with for a quality print is 220ppi, your camera will need to be capable of 52 Megapixels if you want 39"x28". OK, many will say that you could get away with about 160ppi - so a 28Mp would do it. OK....... well perhaps you could get by with a 21Mp sensor.
Of course, the way the image is enlarged to those dimensions is important - standard Photoshop or Elements does a pretty good job, but I'm always hearing how "GenuineFractals" is the program to get.

Try it out, though.... get one of your best pictures, resize to 39"x28" and set the ppi to 200 (use Bicubic Sharper in the resize controls)...... print it at actual size and see what you get. An image is like a bit of elastic - stretch it too far and it breaks (and in the case of a photograph - just looks bad).

[AndyStevens]

I'm still using a Canon 300D in all its 6.3MP glory - and I submit to Alamy (image library for those that dont know). They have strict quality guidelines and insist that all images are 50Mb tiffs which work out at 5120px x 3413px (or at least that's the size I make them to pass Quality Control - and I start with a 3072px x 2048px file). I upsize in the RAW converter and it works fine - I use the 17.5MP option from the 'workflow options' at the bottom of ACR. Depending on your start resolution, you may get an even bigger 'enlargement'. Save As TIFF and the quality should be there - do any final Save As in jpg/10 quality minimum to keep file sizes down and quality up (or keep the TIFF as I do).

Another consideration is the media they are to be printed on - I saw some prints on 10mm thick acrylic sheet yesterday. They looked fabulous and sharp enough to cut your finger - but images would need to be perfect.

For canvas, you can drop right down to 150ppi or even less as the textured surface is very forgiving.