Quote Originally Posted by nworth View Post
Most 40 inch prints are viewed at sufficient distance that the tiny details are somewhat obscured, but I get the impression that you want these prints to stand close inspection. At 20X enlargement, the imperfections of film and lens resolution as well as diffraction begin to become apparent. If possible, going to a larger negative (4X5 or even 8X10) would give a substantial increase in quality even when using a more or less ordinary film like TMX. For example, if you are shooting at f/8, diffraction limits you to about 200 l/mm; a document film like CMS 20 will give you about 250 l/mm; and a good lens for a medium format camera will probably be about 120 l/mm (maybe a bit more). Combined, this yields a resolution of about 95 l/mm, which gives a print resolution of 120 l/in - a quite noticeable degradation at an arms length viewing distance. A decent 4X5 negative and lens with TMX will yield about 80 l/mm on the negative which equates to 203 l/in on the print - still a noticeable degradation, but a lot better. The results for an 8X10 would show no degradation.

Your current plan using MF and CMS 20 film will still probably work well. From the example you showed earlier, I don't think the defects in the enlarged image would be very obvious. Grain would be obvious, so your choice of film is important. But if the equipment is available, a larger negative would give better results.

I was afraid someone would mention 4 x 5 I recently saw an exhibit with prints this size made with a Hasselblad and the detail was very decent even up close. I don't mind a little loss of detail and even some grain, I just want to get the best image possible with the equipement I have (Hasselblad V). I've sent some of my negs out for scanning and should have them back tomorrow. They were done with Rollei Pan 25 and developped in Rodinol, shot on a tripod with cable release, I can barely begin to see the grain with a 15X loop, and the detail is fantastic. They're being scanned on a Heidelberg D7100 at roughly 5400 ppi, and the operator is supposed to be quite experienced. I'll be doing a lot of postprod over the weekend and having them printed next week.

In the meantime I would like to try a high resolution film to compare, but the issue of tonality worries me. How much 'worst' is it compared to 'standard' films like the Rolleipan ? Aren't the Spur and Adotech developpers supposed to make these films suitable for pictorial photography ? And wasn't Tech Pan also considered a document copying film with similar characteristics as CMS (and requiring special developers like Technidol) ?

Paul