Lightroom settings for competition entry requirements

[philliphatcher]

I've been asked to submit photos in 120 dpi format 15x21 cm on a memory stick for a photo competition.

Looking online, I understand that this info is actually for printing so can somebody suggest which settings I should use when exporting the images from Lightroom Classic to put on the memory stick, please?

My current settings are:

Image format - jpeg

Color space - sRGB

Resolution - 300ppi

Thanks

[JohanElzenga]

Choose Export and fill in those details in the 'Image Sizing' box. Keep jpeg and sRGB.

[richardplondon · Accepted solution]

If you enter those figures for Width and Height in the Export dialog (in centimetres) and also if you enter 120 for Resolution (in pixels per inch) - strange to mix units like this, but that's what they want - this defines a maximum "box" into which your image will FIT, so far as how many pixels go into the specially created version which is output.

If your image, as cropped, does not possess that exact 15:21 aspect ratio (shape proportion), an output image will be created which is necessarily smaller in one dimension or in the other. This may be OK, or it may not: the image might need to FILL the requested shape in which case that particular aspect ratio must be used for your crop boundary.

Also it is a good idea to check how these instructions relate to a portrait aspect vs a landscape aspect image. 

[philliphatcher]

Thanks for your clear advice.

[Per Berntsen]

If you enter those figures for Width and Height in the Export dialog (in centimetres) and also if you enter 120 for Resolution (in pixels per inch) - strange to mix units like this, but that's what they want - 

I live in Norway, where we use metric units, but I have never come across pixels per cm. Nobody uses it.

I guess pixels per inch can be considered a world standard.

[elie_dinur]

I wonder if in fact that 120 figure actually does refer to a pixels per cm. parameter (ppc or dpc). The OP says it is "for printing" and if so that resolution, 120 dpi and 720 x1000 pixels, is strangely low for a print.

However, the standard prescription for printing, 300 ppi, would have a metric equivalent of 120 ppc.

I think it likely that the desired resolution is 1,800 x 2,520 pixels.

[richardplondon]

Another possibility:

120 pixels per inch is a reasonable modern update to the more traditional 72 PPI figure (which has long been a notional resolution for computer displays - and was the actual resolution with some Apple displays during the 1980s, IIRC).

In that case the requested centimetre sizing would (roughly) get honoured by a typical modern display, when the image was viewed at 100% pixel zoom.