Great comments, thank you!
There was a test negative with the enlarger. Ainīt anymore. The grayscale card is a great thing, I didnīt think of it. Cause I havenīt any.
A 2-dimensional object it is, does this mean that value 5.6 is enough or should it be say 11 or even 16? As I sharpen with the lens it is the same where I point the focusing area on the poster, everything will look as sharp as it is in the poster? In the nature I choose what area is important to look sharp and what areas I on purpose try to blur out of focus . But shooting a poster is a little different, it is flat. Or is it?
Great that there are active professionals here and you try to help. I think I will stay on this site for a long time. Nnd one day I may give advice to others. That day is not close, I know.....I have so much to learn even in the basic matters.
Since the poster is flat you may not need f/16... Each lens has an optimum f/stop, usually a couple stops down from wide open - maybe 5.6 is the best for your lens, maybe 8...
Do your best to make sure the plane of the film is parallel to the plane of the poster, the depth of field you need is what would take to deal with alignment errors.
And while the lens may not be designed to focus on flat subjects, some lenses have a curved field of focus. Most lenses are not deliberately curved, sometimes it is just a little. If so, you could see it while focusing. That would be a reason to stop down a little more to f/16.
That new Petzval is deliberately designed with a curved field of focus. Don't use a lens like that for this job.
Grayscale can be made of anything. You could draw a charcoal scale if you are an artist. Just find some patches of paper or print that go from black to white with a little bit of everything in-between. Won't be as accurate, but would work the same.
Thank you, Bill. I will make a test card from the leaflet of a paint shop. THey have these small examples of paper where the client can see the color of the paint. I will cut white, gray and black off those, perhaps some colors also to give intermediate tones, red, yellow, blue, green. Then put these on line and shoot my test negative. And this test card is free of charge.
f 5.6 seems to be adequate, sharp from corner to corner at least on my small print size. A bigger enlargement may need 11.
Now back to the darkroom...