Originally Posted by Ed Sukach
also this from the Large format lens testing page.
Scroll down to the discussion near the bottom.
Both web siites are excellent. Thanks for posting them.Quote:
Originally Posted by Robert
I think that it should be noted that, in theory, the *least* diffraction will occur at the largest possible aperture; but it should be noted that that is only one factor affecting the performance of an an optical system.
Be *very* careful about defintitions here - do not confuse "diffraction limits" with something limiting the entire lens performance - "`Diffraction limited at...' indicates that aperture where lens performance will not *improve* by additional `stopping down'". The lens performance could be extremely high to start with ... so any "improvement" would be very difficult to achieve.
The web sites are in FAQ format - and a diligent study of the questions and answers will provide a good education in just what happens when we talk about the phenomenon we call diffraction.
Lens resolution is not *only* affected by diffraction - there are many, many other optical characteristics involved.
Yup that's why I mentioned a perfect lens. I was just trying to show how hard hitting those high numbers would be. One arguement for using the film might be it's better then your lens so you'll get what ever your lens can deliver. OTOH resolution isn't the only thing out there.
I agree with Robert, "resolution isn't the only thing out there".
In B&W, I've come to the conclusion that it's one of the least important factors. Tonal gradation is the most important factor. I recall from my fooling around H&W Control film (1971, I think) is that it produced an incredibly sharp, incredibly terrible print.
I think you should pick your format based on required sharpness for a film giving you what you consider to be good tones. You won't lose much spontaneity using a medium format camera with fast film if, to get the same sharpness, you have to load EI 40 film into your 35mm camera.
Yeah, I also went through a TechPan phase and decided that it was easier and much better simply to use a bigger camera.
There is a review of this film in Black and White Photography, Feb 2004. Julian Busselle reckons enlargements to 20x30 off 35mm film were "still exceedingly sharp"!
Just ordered Gigabit 4X5 sheet film from J&C. At ISO 25, probably not suitable for landscape scenes that may have any motion (wind, water) unless you want to show the motion. I'll probably try it with Brett & Ed Weston type of subject matter. I'll be trying enlargements but wonder if drum scans would even capture its resoving power?
I think last month's Black and White Photography Magazine did a review of it. There was much discussion about the film and its developer. The author had to try a couple times to get the processing down but said it was a tack sharp splendid film.
I use Gigabitfilm from time to time but not anymore in 4x5 only in 35 mm and fast and sharp lenses.
It is actually a very good film for high contrast scenes if I remember correctly it can cover a contrast of 11f stops.
But in the beginning days there has been some troubles with the developer and so I use it only in Xtol now.
There is no grain for focusing by the enlarger part, but I have to do further testing in XTol.
Isn't this gigabit film just a repackaged AGFA copy film? I think I remember seeing that somewhere.
Maybe you could buy it from AGFA cheaper?