Films for Astrophotography

Copyright 2001-2003 Michael A. Covington.
Please link to this page rather than copying it. It will be updated often.
Revised 2003 October 24

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This is a summary of of information that appears in the 1999 edition of Astrophotography for the Amateur, with minor updates.

Note: This is NOT an actual chapter from the book. The information in the book is much more detailed.

(1) Slides or prints?

If you do not have your own darkroom I strongly recommend using color slide film for all types of astrophotography. The reason is that the people who develop the film do not have to make any decisions -- they just develop it and mount it, so "what you see is what you get."

With negative (print) film, the person making the prints has to decide how light or how dark each print should be, and with astronomical pictures, they are often wrong.

You can get good results with color negative film if your local minilab staff are willing to experiment and learn how to make good prints for you. Some labs will do this; some won't. Go to a lab that caters to serious photographers. Even better, Tony and Daphne Hallas do custom developing and printing for astrophotographers.

You can also use Kodak or Fuji workstations (in camera stores) to make prints from slides or negatives, at a cost of about $12 for one 8x10 or two identical 5x7s. Currently, these workstations do not provide contrast control, although they do let you adjust color and brightness.

Black-and-white astrophotography is seldom feasible unless you do your own darkroom work or work closely with a good custom lab.

(2) What a film should be like

Beginners often think the fastest film is automatically the best. (We're photographing faint objects, right?)

Wrong! Fast films are grainy, and they usually suffer severe reciprocity failure. That means their speed falls off in long exposures. The best films for most kinds of astrophotography are in the 100 to 400 speed range.

For lunar and planetary work, you need extremely fine grain, and films in the 25 to 100 speed range are generally best.

For deep-sky photography, you need good reciprocity characteristics, and you also generally need film that is sensitive to hydrogen-alpha light at 656 nanometers. Most black-and-white films do not pick up this wavelength and will not photograph emission nebulae very well.

(3) Recommended color slide films

Fuji Provia 400F and Fuji Sensia II 400 are new products that are getting very good reviews from astrophotographers. This film is twice as fast as Elite Chrome 200 but only very slightly grainier, and it has good reciprocity characteristics. It responds well to hydrogen-alpha, though the response is not as overwhelmingly strong as with the Ektachromes. Contrast is somewhat higher.

This is a considerable improvement over the previous Provia 400 (not 400F), which had less red response and coarser grain.

Kodak Elite Chrome 200 and Kodak Professional Ektachrome E200 Film are my favorites. (These two films are the same emulsion with slightly different aging.)

This film has unusually good reciprocity characteristics (holds it speed well in long exposures) and unusually good response to emission nebulae (which come out bright cherry-red).

Kodak and most other labs will push this film to 640 speed at your request. (This is an "E-6 2-stop push" but the resulting speed is 640, not 800 as you might expect.)

Fuji Provia 400F is a very promising product, twice as fast as E200 but with excellent reciprocity characteristics. I have yet to test it extensively. Apparently, its response to emission nebulae is weaker than E200, but not a lot weaker; this may be a good thing, as it prevents red nebulosity from coming out too bright and featureless.

Kodak E100G is another new product that appears to be considerably better for astrophotography than the earlier products Kodak Elite Chrome 100, Ektachrome Professional E100S, and Ektachrome Professional E100SW, which in turn are not bad either. All of these have very fine grain (E100G extremely fine), good reciprocity (E100G excellent), and strong response to hydrogen alpha. I suggest pushing or preflashing E100G if you use it. It is almost grainless.

Fuji Provia 100F is similar to E100G but with lower contrast and lower sensitivity to 656 nm.

Old-timers will remember many varieties of Fujichrome 100, which has been through many changes over the years. Most versions of it have been reasonably good; in the 1970s it was head and shoulders above its competitors. Currently Fuji makes three varieties. The current Sensia II 100 and Astia varieties are not bad for astrophotography, but Provia 100F beats them both by a considerable margin.

(4) Recommended color print films

The range of suitable color print films is much smaller than it used to be. The Kodak line, except for Max 800, has been redesigned so that none of the films have strong response to hydrogen nebulae at 656 nm. And Max 800 has poor reciprocity performance.

The classic Kodak product line comprising PJM, PPF, PJ400, and Supra 400 has been discontinued.

Tests by Robert Reeves in 1998 showed that Fuji Superia 400 and 800 films outperformed the competitors. They were very sensitive to red nebulosity (unlike Fuji slide films, which generally aren't). However, in the spring of 1999, Fuji Superia was reformulated and apparently lost much of its red sensitivity.

Nonetheless, the Fuji Superia films are probably the best color negative films for astrophotography that are presently available.

(5) Recommended black-and-white films

Kodak Technical Pan Film (2415) is a fantastic material if you can develop it yourself. It is a high-contrast film with ultra-fine grain -- essentially grainless. For lunar and planetary work, develop it to a speed of 25 to 100 in HC-110.

For deep-sky work, it should be baked in hydrogen (hypersensitized, hypered) before use; stored in a freezer, it's good for several weeks after hypering before you use it. You can purchase hypered Technical Pan Film from Lumicon (see ads in Sky and Telescope and Astronomy). Hypering increases the film speed and greatly reduces reciprocity failure.

Technical Pan is the only black-and-white film with useful response to red (hydrogen) nebulosity.

Kodak T-Max 100 is probably the best general-purpose black-and-white film if you can't get Technical Pan. It is fine-grained and has rather good reciprocity characteristics (comparable to the Kodak Spectroscopic films of thirty years ago). It does not respond to hydrogen-alpha.

Kodak T-Max T400 CN and Kodak Black & White + ("Plus 400") are new products, black-and-white films that are developed in color negative chemistry. Your minilab can develop it for you (although some of them refuse to, because they don't believe Kodak's instruction sheet!). Have it sent to Kodak for development and printing.

My preliminary tests indicate unusually good reciprocity characteristics and unusually fine grain. Basically, these are black-and-white versions of PJ400 or Ektapress Multispeed, and we are probably going to find them very useful. They have only partial response to hydrogen-alpha light, but it does record the brighter nebulae.

Do not confuse this with T-Max 400, a conventional film, basically a coarser-grained, faster version of T-Max 100.

(6) Films to avoid

Some films to avoid include:

Kodachrome 200 (very severe reciprocity failure);
all infrared films (because of extreme reciprocity failure);
Tri-X Pan (T-Max 400 beats it on all counts, although I used plenty of it in the past).

(7) Must film be hypered?

If it's Kodak Technical Pan 2415, yes. Otherwise, probably not. Ten years ago, most color films benefited noticeably from hypering (treatment with hydrogen gas). Today, they do not. This is probably connected with the fact that modern color films already have excellent reciprocity characteristics and speed-grain ratio; there just isn't much room for enhancement.

For more information about films for astrophotography, see Astrophotography for the Amateur and the film test web pages maintained by Robert Reeves.