Understanding what size an image would be when using Zoom and how sharp it is in Lightroom

[SteveJL]

I have created an HDR in Lightroom that I need to make some very large prints from - around 5ft x 3 ft. Haven't done such a large print before and want to check the sharpness of the images. How do I do that please?

1) Zoom shows Fit, Fill, 1:1, 1:3 etc - how do I know what size the image will be for each of those - so I can check if it is sharp at various sizes?

2) How do I set a large size like 5ft x 3ft when I actuallt want to print?

Thank you very much - fairly new to Lightroom. First post!

[Peru Bob]

I've moved this from the Using the Community forum (which is the forum for issues using the forums) to the LR forum so that proper help can be offered.

[Conrad C]

You can check the pure image sharpness at 1:1 magnification, which means one image pixel to one screen pixel. On a Retina/HPI display it might be easier to see at 2:1.

However, there is no magnification or view in Lightroom that will preview how sharp the print will be at 5 x 3 feet, because print sharpness depends on the ppi resolution corrected for the print size, plus any output sharpening applied, then corrected for the expected viewing distance (that is, a print viewed at 6 feet only needs half the pixels to look just as sharp as a print viewed at 3 feet).

That is all difficult to guess or simulate on screen, so if this you are going to spend a lot of money on these prints, it will be worth doing a test print. If you are using Lightroom (not Lightroom Classic), that application cannot print and does not have advanced enlargement features, so you will want to edit the image in Photoshop by scaling it up to the print size, then do a test print from Photoshop of a small section of the enlarged version.

Then, if needed, you can adjust by applying traditional Photoshop upscaling and sharpening techniques. If necessary you could also run it through the new Super Resolution feature in Camera Raw (part of Photoshop), which can be useful for preserving detail for extreme enlargements.

[SteveJL]

Hi Conrad, Thank you very much for that - apologies for the slow response - I was away. I do have Lightroom CC (is that Classic? it says 2015, so presumably that was when I took it out, but haven't used for two years) so would I be able to print a 5' x 3' from there please?

I do have Photoshop but have only ever used the lasso tool, but I think I might have a go anyway to print from there. Is there a max sharpening that you would recommend please?

NB The photo is of a very large window in my flat and the view outside. The photo will be mounted and hung very high up on a wall - 15 feet from the kitchen floor. The idea is to make it look as if there is a window with a view in a very strange place in the flat. Presumably at that distance sharpness will not be quite such an issue?

Thank you so much for your help - learning loads!