Resolution - a few 400 speed films under the loupe

[Gerald C Koch]

Why not just look at some prints you have made from TriX and Delta 400 and make a judgment about which look you would prefer for the project at hand? Unless you think that the two films are identical except as some level only a quantitative analysis along the lines you are suggesting would reveal.

There is a basic problem with using prints. What people see and think is grain is actually the irregular spaces between the grains in the negative. Remember you are looking at a positive image when looking at a print.

Another problem is that by using a print a host of other variables are tossed into the mix. They are the resolution of the enlarging lens, paper, enlarger vibration. gamma value for the print, ... (Read the paper cited below.)

I know that Kodak uses the Modulation Transfer Function to measure the resolution of its films and publishes the results.

http://www.normankoren.com/Tutorials/MTF.html

What explains this urge on the part of some APUGers to test and measure things that they have neither the training nor equipment to use. I for one am perfectly content to let the manufacturers do the work. All in all a very strange mix of hubris and masochism.

 

[NJH]

Agree 100% Gerald. What always seems to be missed though is that when guys do these tests without shooting a resolution target they are in fact always doing sharpness tests. The giveaway is straight in the opening when guys say stuff like I used my 10x loupe or I did a 20x16 enlargement. The resolution scale is instantly fixed then one is comparing how a particular subject looks in the results at that resolution scale. The formal equivalent is to find the scale along the right on the MTF graph equivalent to the features of interest and read off how much contrast is maintained where the line sits on the Y axis. Its just a shame that only Kodak seem to publish these graphs now, I tried the other day but could only find some historical data for other films.

I don't have a problem with sharpness comparisons as they are vastly more photographically relevant than extreme resolution tests, looking at the numbers like 60 lp/mm on 35mm relates directly to the impression of well resolved fine detail at typical viewing distances (hence why lens manufacturers use these numbers on their graphs).

 

[faberryman]

What explains this urge on the part of some APUGers to test and measure things that they have neither the training nor equipment to use. I for one am perfectly content to let the manufacturers do the work. All in all a very strange mix of hubris and masochism.

What do you rely on when choosing a particular film for a project?

 

[LAG]

Did you guys notice this thread is 8+ years old? Why do zombie threads like this come back?

It ain't over till the fat lady sings

 

[Photo Engineer]

What do you rely on when choosing a particular film for a project?

Whether the results suit me or not!

However, I have a complete array of test equipment here that I know how to use, and I know how to interpret the results. I seldom use them. The results are what counts.

PE