Traditional vs. T-Grain

What are the differences between T-grain and traditional grain

emulsions? Are Delta films T Grain?

 

 

Thanks

Delta T grain? Yes.

Johnny, there are major differences in the shape/size of the silver grains. Traditional silver film has grains shaped like, eg. boulders on the beach, tabular grain film has larger, flatter grains, like slabs of slate. (Crude analogy, but you know what I mean.) Because the grains are larger, they will react to light more easily, and so the makers introduce a dye to reduce the sensitvity, which you need to remove. Some people advocate extra fixing, and although this will indeed remove the dye, too long in an acid fix won't do your sensitive film any favours. Extra washing is the best bet. Your developing procedure needs to be up to scratch, too. Sloppy technique as regards time and temperature can result in blocked shadows and burned highlights. Contrast is a tad higher with T-grain films, too. Having said all that, I use Ilford Delta lot, and have had some truly amazing results. (Delta and T-Max) are both T-grain.)The first 5 images in the gallery page of my website www.monochromephotography.com are Delta 400.

Peter.

All this is correct. T-grain films are more sensitive to variations in developer temperature, time, dilution, agitation etc. So for a beginner I recommend to start with traditional films. After you get the knack of processing you can change to t-grain emulsion if you feel the need for it.

Dyes are put into films for two reasons: 1. to control speed or tweak it during manufacturing - this is used in color film mainly to balance the 3 layers to each other, but rarely in B&W films. That is why the color film dyes that wash out are colored. and 2. to increase sharpness by absorbing multiple internal reflections much as an antihalation layer does except this is in the film layer.

 

T-Grain films can be built to the correct speed without using speed tweaking dyes if they are used for B&W.

 

T-Grain film develops much the same as K-Grain film ("klunker" - they can be cubes, octahedra, or just random boulders as well as other shapes such as rods and spheres). They can have more or less contrast simply by design or have more or less developability just as current K-Grain film has. They do respond slightly differently to most developers simply because they are different films.

 

The objective of using T-Grains is to give better grain at the same speed as a similar K-Grain film, with no sacrifice in tone scale. The addition of dye is the effort to improve sharpness as well at this given speed and curve shape.

 

If you observe a different curve shape (tone scale) you should adjust development time as recommended by the manufacturer. I have used T-Max, TX, HP5 and Delta and find that they are all good films, with the Ilford films slightly more grainy but comparable overall otherwise. I used D-76 for all, at the recommended development time for each film. Tone scale and speed were a close match in all cases.

 

Ron Mowrey

While Ilford's Delta films are of a more contemporary design than FP4+, HP5+ and others, they are *not* T-grain films. They are epitaxial-grain films. Different engineering, different response to exposure and processing, different look. T-grain refers specifically to Kodak's proprietary design.

 

Compare Delta 100 with TMX and you'll readily see the difference in print, in scans, even in the negatives if you know what to look for.

Lex;

 

In the case of epitaxy, it can be grown, and usually is grown on T-grains to start with.

 

Ron Mowrey

I agree with all that has been said thus far but would add my subjective and probably

controversial opinion that the modern emulsion films such as Tmax, Fuji Acros and to a

lesser degree the Ilford Delta films seem to sacrifice tonal qulity(especially local contrast

and highlight detail) for finer grain. That's my experience anyway. That's the main reason

I use Agfa APX 100 these days.

local contrast and highlight detail are up to the person who exposes/developes the film.

And Anchell & Troop would agree with Tariq. Modern emulsions like T-Max, Delta, and Acros suffer (and this is without question a disadvantage...) from excessively high microcontrast. In effect, highlight detail is sacrificed because the grain clumps in high-density areas do not scatter light as they do in conventional grain films. Rather, specular reflection of the light results and this prevents discrimination of fine highlight detail.

 

There is *no* complete remedy for this, btw, it is a consequence of the grain technology.

Al;

 

Micro vs macro contrast arises from adjacency effects and are described in A&T and examples are given in Mees "The Theory of the Photographic Process". Clumping of the grains has nothing do do with adjacency effects, restrainers and inhibitors control that effect. Clumping also has nothing to do with macro vs micro contrast. You might want to see the examples of this in the enlarged photos published by Ctein in "Post Exposure".

 

So, what evidence do you have to offer to support your comment? I have never seen any evidence to support this, but I have heard some comments similar to yours here.

 

Ron Mowrey

Ron - I misspoke concerning the clumping. What I meant to say is that according to A&T in the Film Developing Cookbook the large lateral dimensions of tabular grains do not scatter light as well as conventional grains when there is an abrupt change in the exposure level received. So microcontrast is higher and fine highlight detail can be difficult to print.

 

I have Ctein's book on my shelf, as yet unopened, but I will give a look-see for more information. But again, here I am relying on A&T - and trusting that they have some sort of info. to back up their allegation.

Al;

 

You do not want light scatter. That causes multiple internal reflections which decrease sharpness. This lowers micro contrast.

 

T-Grains, which are thin, can allow light to pass through them like a partially silvered mirror, and therefore micro contrast is more normal than in a film with K-grains.

 

I'm not sure what you are getting at, but from my standpoint, the T-grain seems as if it should be better, as it reduces scatter which in K-grain films decreases micro contrast.

 

The goal is to have sharp delineation at the edges of an object, with micro and macro contrast nearly equal. I say nearly, because micro contrast should always be higher than macro contrast to preserve sharpness as size decreases and nears the resolving power of the film.

 

Does that help?

 

Ron Mowrey

I think the Technical Reason that Traditional emulsions retain Highlight detail and exhibit

Local(Micro) contrast better when compared to Modern(new tech) Emulsions is due to the

fact that, in general, Modern films have more of a straight line film curve with less of a

noticeable toe and shoulder than traditional films. I don't know if this is due to the

diffusion effects of light scattering in the grain or not but that seems to make sense.