Lightroom export settings

[Basu1947]

There are two setting while exporting images from Lightroom for printing. I wonder if you can shed light on their significance and how to use those settings:

1. Image sizing -> Resolution (Pixels per inch). I experimented with a 18x12 image and printed the same image 200, 250 and 300 pixels per inch. I could not tell any difference between the three images. Is there a rule of thumb as to what setting should be used for what sized print?

2. File Settings->Bit Depth. What is this about? There are two choices 8 bits/component and 16 bits/per component. When do we use 8 bits and when do we use 16 bits?

Thank you for sharing your knowledge.

[Mike Buckley]

I'm not good at explaining bit depth so I'll only handle your first question.

It's understandable that you were not able to discern a difference between printing at 200, 250 and 300 pixels per inch. That's because 200 pixels per inch will usually be fine and 300 pixels per inch is being super safe. I always print at 300 pixels per inch because I like the comfort of knowing that I'm being super safe.

Others with more knowledge than me will be able to give you a scientific explanation of why that's so but I'll limit my post to the practicalities of the above.

[Manfred M]

Hi Basu -

The native resolution of Canon and HP printers is 300 dpi (dots per inch). If you use an Epson printer, it is 360 dpi. Setting your image to native resolution means no interpolation on the part of the printer = higher accuracy. Generally going to native resolution is the cleanest way to transfer data with no chance of errors being introduced.

Bit depth is related to colour accuracy. If you shoot jpegs, these are 8-bit, so sticking to that setting is fine. If you shoot RAW, your camera will output either 12-bit or 14-bit images (the data is packed with "0"s to create 16-bit images). If you work in 16-bit, Lightroom will preserve all the the pixels that your camera recorded and will give you better results. If you convert to 8-bit and manipulate the image in Lightroom, you might find problems with "blocking" or other artifacts.

Even if you end up saving to jpegs, that should be the very last step in your post-processing workflow, as throwing away data in the end will have minimal effect on the output image.

I hope that this makes sense to you...

[Basu1947]

Thanks for the explanation. Based on your explanation I have sent a message to Adorama (my printer of choice) what is best number of pixels/inch for their printers.

I do shoot in raw and I had been using 16 bits then cut back to 8 bits because the TIFF Files with 16 bits for an image 36x24 is about 440 MB. Now I'll start using 16 bits. Any suggestion as to how to cope with those gigantic TIFF files?

[Manfred M]

Any suggestion as to how to cope with those gigantic TIFF files?

Don't use TIFF for your final output. Most printers are setu up to use sRGB jpegs. Your average print is limited to about 4 EV in dynamic range and a few hundred thousand colour shades (much less than your screen shows).

[Mike Buckley]

Interesting explanation, Manfred. I hadn't thought about printers having a native resolution though I suppose every output device has to have one and that all other resolutions are interpolated.

I like Basu's idea of contacting the printing company to determine their recommended resolution. That's because the person operating the printing machine can change its resolution. I imagine that it's best to send the company the resolution that the operator will use but you might advise that it's actually better to match the native resolution even if the operator uses a different one.

[Manfred M]

Mike - I've also read that settings that are even ratios of the native resolution give good results (1/2 x or 2 x), but have never bothered.

The other reason to contact your printer is to get the ICC profile for the printer they are using. You need that if you want to soft proof.

[Basu1947]

Manfred:

I heard about printer profile and its purpose - is that the same as ICC profile? Once I get the profile from the printer, how do I use it?

Basu

[Manfred M]

I'm not an expert in Lightroom, as I tend to work in Photoshop whenever I can.

You do have to load the icc profile from your printer (this is specific to both the paper and printer used; I'm not sure where these are located for Lightroom) and check the "Soft proof" box in the Develop Module. This will give you a reasonable emulation of what the final print will look like (assuming that your screen is calibrated and profiled). You may need to make an adjustment to your screen's brightness to match what your printer provides (trial and error). This will show you any place that you get highlight clipping or loss of detail in shadow areas, so that you can make adjustments.

The highlights are more important, as anyplace that has a white value of 245 - 250 or higher will not have any ink deposited during the printing process. This will make your image look a bit patchy in those areas.