This time topic quite new for me. I want to print my photos bigger than A3 format.
Normally for printing I do the following:
Process RAW in darktable, export it as TIFF, JPG (depends)
Create an image in GIMP with size that equals print size (300 dpi)
Insert image as layer and scaling it down leaving some margins (to my taste)
Adding signature to photo and description at the bottom margin.
There you go!
It works nice up to A3 print. But for bigger ones I need to scale up, not scale down my photo.
Haven’t done that and those prints are quite expensive (oh, Fine Art papers…) thus not much left for experimenting.
All done in Linux.
Do you have any good practices for the upscaling the image for the print?
If there were no fonts there won’t be a problem. I would then leave the upscaling to the service. But I don’t want to scale the fonts too.
Coincidentally I just added an upscaler to g’mic called Upscale [edge]. More for my own interest in algorithms than particular use. Anyway, here’s what it does to that (on the fuzzy side to say the least):
I do often print on 13 x 19 paper using an Epson Photo printer. The printer dithers (up yo 4200 dpi and as a result I am not noticing any problems with scaling.
My output from dt is directly from the RAW to print so I am avoiding transfers to Gimp and avoiding the use of an outside print service.
I try to stick with very few papers and those that I do use are calibrated for my printer. Print preview in dt works well and allows fine color tuning if needed.
Has anyone tried a stair stepping method for upscale? I’ve found stair stepping in either 10 or 20% increments (bicubic sharper) when downscaling gives best results, not requiring any post resize sharpening. In fact, the only reason you might choose 20% instead of 10 is that depending on how small you resize, 10 can sometimes appear oversharp! However I have not yet tried this for upscaling.
Thanks for all the answers!
I did research on this and found interesting and quite simple answer. It is more pragmatic than theoretical
I do not need to upscale x2 or more, rather 20% or so (so that dpi won’t drop below 200) thus am quite happy with:
Upscale layer (the embedded photo) to my taste
Sharpen it a bit with radius 3 (since printer’s dpi is x3 than display usually)
Key ingredient - noise. Adding a bit of HSL noise (just luminance)
The prints won’t be huge. Just 30x45cm or 40x53cm. They will be viewed from 1-2 meters thus dpi for a photo could go to around 200. In 2-3 weeks I will know if that works.
@black_daveth I’m aware of that I usually sign my prints and give them white frame. So yes, the whole document is set to destination size at 300dpi then the photo is pasted as layer. The signature (and description) is set to specific size and should not raise too much attention. If I scale a document prepared for A4 the signature could look ugly.