the blur spot diameter = circle of confusion, right?
so i set it to 40microns (39mpx hasselblad back)
lp/mm for print resolution? how does this convert into ppi?
are 10 lp/mm equal to 508ppi? if i assume, that one line is equal to one pixel...
let's say my usual print size is 17x24 at 300ppi - what would i have to dial in to get that?
i'm a littlebit confused by that.
You need to go into settings (cog symbol) and specify your print size. The 10 LPM default is probably perfectly adequate, since it is judged so for close viewing of a small print, but what specifying the print width does is ensure that the resolution doesn't drop as you print bigger. In other words, you can stay just as close to the print. But I am going to test this and see if it holds true. I will also experiment with 12 and 14LPM but you will notice that as you specify tighter resolutions, the DOF drops to almost nothing.
COC wise I have been setting 41 microns for the IQ180.
I think the answer is that, at root, DOF is about 'acceptable' focus and the word 'acceptable' means 'personal'. To that extent, this app seems to let you decide what that personal degree of acceptability is, with some default good guidelines. Thereafter it's going to be a tweak-athon!
But the way I am looking at it is that 1 line pair = 2 pixels width. If I don't want to see individual pixels then I need to print at about 200 DPI or higher (I often make very large prints at 180 DPI so that's about right). That means that 1 line pair per mm = 2 pixels per mm = 51 pixels per inch. So 10 line pairs per mm, which is the default, = 510 DPI which is as you calculated... so I reckon that if you set 4 lppmm you will get about a 204dpi print, which is about the same as a 50% view on a 100 dpi monitor and about the lowest I will drop to in print. I will compromise on 5 lppm for now, close to 260 dpi and that should be enough for big prints even reasonably close up.
To put it another way: the largest print I have made so far is 1.25 metres high. It looks really good even very close up. So let's say that's 50" wide.
IQ180 resolution is 10328 pixels on the long side and that is a print resolution therefore of 206 dpi - the same as 4 lppmm if my math is right. So setting 5 should be absolutely fine, when using the largest print size.
That means that with the Rodie 40 on the IQ 180 (and assuming a print size of 1 metre, which is the maximum allowed on the slider but remember I have chosen to use 5 lppmm rather than 4 so that should allow roughly 125% bigger print which takes me to my desired size) shot at:
F5.6 the hyperfocal distance is a touch under 15 metres and that gives good focus from about 7.7 metres outwards.
F8 it is about 11.5 metres and that gives good focus from about 5.8 metres outwards.
F11, which is the absolute smallest aperture I would use (the calculator shows that at F16 diffraction ruins everything!) the hyperfocal is 10 meters and the near distance is 5 meters. I am going to write those values down and put them on a card!
There! I don't need a Disto any more. But I'm going to get one ;-)
Anyone who now wants to show me the errors in my calculation is extremely welcome!