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Thread: Large prints and pixel dimensions

  1. #1
    DH59's Avatar
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    Diane

    Large prints and pixel dimensions

    Hi, I did a portrait session recently and the customer wants a 20"x16" print to place in a frame that they already have (doesn't sound as if there will be any mount surrounding it, but that's another issue) to put on their wall.

    My camera is a 40D and the native pixel dimensions are 3888x2592. I will have to have this image printed at a lab, and the one I was thinking of using has stated that the file needs to be at 254ppi, which is the native resolution of their printing equipment, but at 20x16 the image size in pixels is stated on their website as being 5080x4064 with a file size of 59Mb.

    I have Lightroom and Elements 9, so what is the best way of getting the image to meet the lab's requirements?

    I did crop the image slightly in Lightroom to improve composition, so the actual image she viewed was only 3075x2050. Even though the LR crop is set to 'original' it always reduces the file dimensions. Would I be better to crop in Elements in order to keep original image dimensions?

  2. #2

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    Remco

    Re: Large prints and pixel dimensions

    First, you will have to do another crop, to get the aspect ratio you need (customer wants 20:16 = 5:4, what you mention is 3:2, or 6:4).
    That would get you an image of either 2562x2050, or 3075x2460 pixels (depending which dimension you keep from your original crop),
    which would translate to 125-150 ppi.

    Next, are those 254 dpi a hard requirement or a recommendation?
    If they are a hard requirement, you can upsample your image to the required dimensions (Elements should be able to do that, no idea about Lightroom).
    If it's only a recommendation, you can let the lab handle the file as is, or upsample. To keep the lab happy, upsampling might be the easiest way.

    Don't worry about the quality of the print (if the base image is good of course ), that 20x16 print isn't going to be viewed from 30 cm...
    The 254 ppi is optimal for a viewing distance of about 30 cm (for persons with good eye sight), if the print is watched from 1m, 100 ppi should be more than enough already.

    Remco

  3. #3
    DH59's Avatar
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    Diane

    Re: Large prints and pixel dimensions

    Thanks Remco.

    So I need to do something else when cropping to get 20x16? OK I will give that a try. Lightroom is configured to 240ppi when outputting files, so perhaps I also need to change that in preferences.

    The 254ppi is the stated requirement on the lab's website as the native resolution of their equipment. I can select an export resolution in Lightroom, so that could be an option.

    As for the quality - well, I am just beginning on this portrait business journey, but the base image looks OK to me.

    Will have a play and see what happens.

    Thanks again.

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