What's the point of comparing two black-and-white films that are not available anymore? Somebody emailed me with that question several years ago. It was still interesting to do this comparison, and who knows when you might get into an argument between b&w photo-geeks and need a source to back you up?

These are the results of a comparison I did between the Agfa APX 25 and the Kodak Technical Pan. Both are black and white films with extremely fine grain, so I wanted to know which is better. This page reports the results of this comparison and also includes some points that came out of a discussion after I posted my results to the german-speaking newsgroup de.rec.fotografie.

The Techical Pan is usually used for reproductions of drawings and other applications that require a very fine grain and extremely high contrast. But it can be developed to be used for pictorial photography as well. It is said to be the finest grain film available today. Well, we'll see ...

This is a practical test to see which film has finer grain under the circumstances I will use it in. This is clearly not a scientific study, but you should get similar results when using reasonable amateur equipment. If your equipment is much better, your results might be different.

Methodology

The comparison was done with the 35mm versions of the films to be compared. They were exposed with the same time/f-stop combination using the same lens mounted to different bodies. Here is a summary of the exposure data:

Lens:	Nikkor AI 2.8/24
F-Stop:	8
Exposure Time:	1/30s (I think)
Camera:	Nikon FE-2 and FT-2
Tripod:	Manfrotto 055CB with head 141RC

The films were developed in a small tank according to the recommendations in the datasheets (which are available for the APX 25 (PDF) and the Technical Pan (HTML and PDF)). Here is the data (all at 20°C):

	Agfa APX 25	Kodak Technical Pan
Developer:	Agfa Rodinal 1+50	Kodak Technidol
Duration:	10 min	9 min
Agitation:	continously first minute, then four inversions every 30s	10-12 times up and down in 2s every 30s

The negatives were then enlarged to the same magnification (about 16 times the size of the negative, 59x39 cm (about 23x15 in)) and the prints were scanned in (with an Agfa SnapScan at 300 dpi).

Results

You can look at the detail images below.

In these images, you can see that the APX 25 is slightly sharper than the Technical Pan. There is no visible grain in either of the images. But due to the limitations of the process, I would call it a draw ...

What you cannot see, is that the APX 25 needs about ½ f-stop less to reach the same grey level on the paper (grade 3) than the Technical Pan. I can never figure out what that means in terms of densitometry, so I leave that as an exercise to the reader ...

I also had to refocus the enlarger after putting in the other film. I don't quite understand why this is necessary, since the emulsion should be at the same position no matter how thick the film carrier is (the Technical Pan is supposedly thinner).

Using the grain focuser, you can see the grain, but only as a pattern, not really the single grains. It looks like a 100 ASA film enlarged to 13x18 cm (5x7 in). I will make a comparison with a microscope when I get a chance.

Images

These are scans from the prints that were not sharpened or unsharp masked in order not to introduce any artifacts (but they probably appear to be a bit blurrier than they really are). The bottom images show a detail that is about 0.74mm big on the negative (or about 3% of the shorter side of the negative). Each pixel has a size of about 2.5 µm x 2.5 µm on the negative. This is the maximum I could do with the equipment I have access to.

Agfa APX 25	Kodak Technical Pan

Discussion

The two films are almost identical, safe for the slight difference in density (which can easily be corrected by adjusting development). Up to an enlargement of about 16-fold there is no visible difference, and even small details are very precisely depicted. The APX 25 seems to be slightly sharper, but that is difficult to say.

But if you take the cost of the films into account, the APX 25 is the clear winner: It costs only about one third of the Technical Pan, and Rodinal is also much cheaper than Technidol (and Rodinal can also be used for many other films). With Technidol, you also have to develop two films at the same time, because it comes in small bottles for two films and cannot be stored.