Tri-X up to 12800 ISo with diluted D-76

I am interested in astrophotography and searching on the web I found this interesting technique for pushing Tri-X.
Has anybody tried it? Seems simple and very economical.

Well, TMY-2 has higher resolution and finer grain.
And XTOL developer is sharper, and finer grained.
But who is to argue with TriX and D76 ?
It is very neat, but you CAN do better.
Bonus points for checking it out on dry land
before trying it out on the starship.

One problem. The author's correlation of time, dilution, and speed
assumes that Tri-X and D-76 yield a 1:1, linear curve.
It doesn't. Kodak's chart is self explanatory.
So, you aren't increasing the opacity of the negative
at the same rate you are increasing the exposure index.
But the method works because you are increasing the
CONTRAST, and relying on the contrast increase,
to lift your 'underexposed' stars to printable densities.
Since you don't need a continuous toned negative, the method works.

Look at the set of Kodak's curves.
As you increase the development time,
you increase the contrast of the film. The more the exposure,
the greater the increase of negative opacity as you increase
development time. So, depending on the actual tonal
placement (exposure), you will be successful or not.

All that is incorrect about the author's method
is the explanation. Thank Kodak for the science and the author
for recognizing a darned good way to shoot stars !

Diluting 76 is useful, increasing the acutance, but the extreme dilution of D76 is counterproductive.
Beyond 1+2, you don’t achieve much acutance gain, and you have to develop longer and longer
to increase your highlight density increase. The claim of compensation is faulty,
since you are increasing the highlight contrast, the exact opposite of compensation.
The process works, however, because of the inately long scale of Tri X.

The combination of TMY-2 and XTOL is superior to Tri-X and D-76
because TMY-2 has a longer tonal range, it has significantly higher acutance,
and finer granularity. XTOL yields higher film speed and less grain than D-76.
Shoot TMY-2 at 3200, develop it at 75˚ for 10 minutes (Kodak’s data).
15 minutes would probably get you up to 6400. Straight XTOL will get you as high as you want to go.

Or use the author's methods as it sits, and have fun !

Thanx for the very detailed reply! I already have a roll of Tri-X and D-76 so I will give a try to the author's method after that I will try T-max and XTOL as you sugest. Well experimenting is all the fun

Sorry to nitpick, but 6400 then 12*500*, just like Plus-X is 125 instead of 128.

I'd recommend a T-Max film developed in T-Max developer for the best results. IDK whose chart is being used that tracks photodevelopers here in this thread, but a chart I've seen on a dedicated astrophotography website, from Kodak (you can find it if you look on the HC-110 unofficial resource guide) shows that T-Max Developer produces some of the highest *true film speed* with T-Max films, making it ideal for astrophotography usage. Maybe the reason that T-Max doesn't seem to produce the best speed here is that Tri-X behaves differently than the T-Max line.

You should consider two or three other films over Tri-X for several reasons.

TMY-2 has 50% more sensitivity than Tri-X to hydrogen alpha wavelengths, prevalent in many of the most sought after emission nebulae. It also has less reciprocity failure.

Ilford HP5+ is also worth a try, besting Tri-X and the older version of TMY in H-alpha sensitivity and reciprocity characteristics.

I'm with df cardwell on the dilution issue. The main point of the method described is to increase contrast, and greater dilution is working against that.

For a good B&W film comparison for astrophotography, although done several years ago, see http://www.robertreeves.com/b&w.htm Note that the T400CN mentioned there is a chromogenic film, C-41 process as with most color negative films.

Lee

few days ago I was reading somewhere about press photographers using Tri-X at around 6400 using HC-110 REPLENISHER at 1:15 for like 15 minutes?

Taking back that 15 minutes estimation. Too many numbers to keep straight right now. You can probably find something on it if do a search, though.
Covingtoninnovations.com 5 min. at 75 degrees

Got question concerning HC-110 replenisher
I read along with some of this other press photo tips/tricks that old -at least- HC-110 replenisher contained Pyro. It seems to have been reformulated a few times?
Any Pyro in it and would that even help in pushing a film that far?

that's it for me, thanks

sun of sand said:

few days ago I was reading somewhere about press photographers using Tri-X at around 6400 using HC-110 REPLENISHER at 1:15 for like 15 minutes?

Click to expand...

shooting football in the rain for newsprint repro in 1968 is one thing...

Back in the late 1960's a smart trick was to rate Tri-X at ASA3200 and develop it in D76 diluted 1+3. Development involved inversion agitation of the tank for 30 seconds and then putting it down and walking away for a day.

24 or so hours later a standard stop/fix/wash yielded occasionally interesting negatives. I've just had a look at some of those negs and I reckon the 3200 speed was a delusion; maybe 1600 tops for the highlights and still zilch for the deep shadows.

It all felt clever at the time until a pal of mine reckoned he could shoot Ilford HP-4 at 4000. Another delusion as it turned out. If there really was more true hidden speed in film the marketing guys would have the value printed on the box in big numerals.

One thing you might try, is pre or post flashing your film to give a density of .05 to .10 with the developer/film/time combination you choose. Doing this gives the film a littlle more than threshold exposure so any exposure from your subject will be recorded on the film.

I guess the same technique may be applied to HP5+. It's a convetional emulsion film not a T-grain one like T-Max and Delta. I know the preflashing method read about it in the little book "Increasing film speed" but seems tricky to master...
This hypering method seems interesting too. It's for the obsolete 2415 but may worth a try on other films too...