Tri-x at 80 asa

[johannes_reiter]

Hi,

 

I'm a beginner to black and white photography and in-house processing

of negative and print, this is why I browse through as many forums as

possible trying to gather information, ideas alternative working

methods upon which I can build my expewrience.

 

Whilst reading through a German forum I came across a thread in which

somebody develops Tri-x at 80 asa, which apparantly to him was

general practice, none of the answers where questioning the fact why

he developped tri-y at 80 asa, hence my question here.... why would

somebody develop Tri-x at 80 asa ?

 

Is there an apparent reason for that, does this enhance something ?

 

I would be most gratefull for any input on this.

 

I would ask the ask the guy in question, but my command of German is

generally low, and none German speakers on German forums are

generally not appreciated.... hence my post here ...

 

Kindest regards

 

Johannes

[trooper]

Over many years, I have heard/read some very skilled and learned technicians declare that Tri-X's true speed is in that range. If you are looking for extreme shadow detail, there are developer combinations that will generate that sort of true speed. Most people readily agree that 320 is a reasonable expectation for general duty and printing needs, so 80 is just 2 stops different. The algebraic progression of the ASA speeds tend to warp our perspective, too. I've used developers that give me great mid and highlight tones but require this sort of exposure (along with developing time/temperature tuning) to open up the shadow end of the curve to take advantage of the look that I like in the other tones.

[daniel_gregory]

I have done a bunch of film speed testing on Trix 120 rolls. At the 320 ASA speed, most of

my density testing put the film speed in the 100-200 range for N, N+, and N-

development times. The more exposure you can get on the film the more options you will

have in the darkroom to print the image. My speeds are what my developer, camera, lens

require to get the correct zone densities on the lower end of the scale. There is a lot of

testing that you can do to find the correct EI for your film (which can come from a film

speed test, experience etc.). My guess is that over time the german poster has found that

in his setup, 80 EI give him the correct shadow density to get the necessary data onto the

negative. Normally a zone III placement will render full details (actual required density is

different from 120/35 and sheet film and also affected by enlarger type), any less and that

area of the image lacks sufficent detail to render the shadow detail.

 

I would take a look at www.zonesystem.com they have a lot of good examples on film

speed etc as it relates to getting shawdow detail on the film. the value and importance of

film density which is what we are really taking about here is at http://

www.zonesystem.com/chapter5/a.html

 

Finally a true EI or film speed is almost never that of the MR ASA, this goes for color and b

and w. Shooting the MR ASA will normally underexpose your shots.

[rick_jones5]

You expose any film based on what works best under your working conditions using the peculiarities of your equipment. Your developer may not give full speed (Microdol X might require as much as an additional stop of exposure) 400 - 1 = 200. A condenser enlarger might require 20-25% reduced development from what manu suggests requiring additional exposure to retain adequate shadow detail. 200 - 1 = 100. Your light meter might tend to under expose by a stop requiring a lowering of the meters ISO scale to compensate (100 - 1 = 50). Other variables that could require a speed adjustment would be fast or slow shutter speeds or even inaccurate lens apertures. In my experience, you can't go too far wrong if you give generous exposure as long as you guard against over developing. So, yes, I can see why 80 might work for some people.

[chris_waller]

The reason for downrating film, i.e. increasing exposure and reducing development, is to reduce the contrast of the negative and thus be able to capture a greater subject brightness range without blocking up the highlights or getting empty shadows. I typically rate HP5 at 160 ASA but on extremely bright days, and where the subject matter has a full range of tones, I have exposed it as low as 80 ASA.

[johannes_reiter]

wow, thank you, I'm beginning to understand the principle now..... I will have to try it out.

 

What are the developpers to take full advantage of this kind of process ?

 

I currently use D-76 for my (400 rated) Tri-x'es and Rodinal for my APX 100.

[bruno]

Just think it might be a typo... I've done some tests as well, and came for a true speed of TriX in Xtol 1+1 between 250 and 320 asa.

 

I tried to pull the film overexposing and underdeveloping: you will get no separations in the midtones. I.e. if you have a portrait of someone in a sunny day, you will get a lots of details in shadows and highlights, but his face will be completely flat.

 

It depends on the use. I still had the best overall appearance of TriX around 320-400 asa.

[arjen van de merwe]

I have used a lot of Tri-x in D76. Good combination. I mostly use it at iso160. Rating it slower gives you finer grain and lower contrast. This means that you get a lot of information in the negative. But it is not easy to make a good print from such a negative. You have to print at high paper grades, and you have to be meticulous about the exposure times in the darkroom. This is especially difficult when you have to do some critical dodging or burning. Not a beginners job, I'd say. Such negatives scan beautifully, by the way. Working in photoshop or other image editing software is easier than printing in a wet darkroom.

[william_linne]

Years ago, I was hired by a nightclub to shoot some photos during one of their big theme nights. I used tri-x rated at 50 and a big metz flash gun with my pentax 67. I pulled the film 3 stops during processing and it really smoothed out the photos. No "deer in the headlights" look. Lots of shadow details. Very nice look.

 

william