Richard, I appreciate your taking the time to say all that. I hadn't a clue before what "toe" meant, but now I see. Anyway, I want you to know that I intend to read this again and more thoughtfully - so you know your time isn't wasted. I'm off and running now but may comment in response late. Thanks again!
Janet On Mar 21, 2008, at 9:42 AM, Richard Knoppow wrote:
----- Original Message ----- From: "Janet Cull" <jcull@xxxxxxxxxxxxx> To: <pure-silver@xxxxxxxxxxxxx> Sent: Friday, March 21, 2008 5:34 AM Subject: [pure-silver] Re: Kodak vs IlfordWhen you say, coarse and fine grain, do you mean grain that in the print will show up as much grain and/or little grain? Grainy *looking* or smooth? I don't want to assume I know what you mean, because I'm not always sure I do.The greatest effect on grain is the characteristic of the emulsion. Developers have an effect, but it is relatively small compared to the built-in grain of the emulsion. Despite much improvement in emulsion technology the old rule still applies: faster film is grainier than slower film. Tabular grain films, for various reasons, tend to have finer grain for a given speed than conventional grain films. Also, the current T-grain films, Kodak T- Max, Ilford Delta, and Fuji Acros, all have relatively thin emulsions which leads to greater resolution and sharpness (they are not the same). However, partly because of the thinner emulsions, they tend to be fussier about control in processing. The curve shape of the emulsion also is controlled by the way its manufactured. The developer can have a relatively minor effect on the curve but does not fundamentally change it. The exception is when a special purpose developer of the "compensating" type is used, or stagnant development is used, which tends to limit the development of the denser areas of the negative hence lowering the highlight contrast. While many feel that this yeilds better highlight detail it can also limit detail because the highlight contrast is too low for variations in density to be visible. The problem here is really the limit of density range of the usual reflection print which can not reproduce the full range of brightness of many subjects, or even get near to it. The eye tends to judge the quality of an image by the mid-gray values so that, unless the highlights are obviously completely blown out, and unless the shadows are completely dark where the eye expects some detail, the image will be acceptable where a low contrast image embodying a wider range of subject values will look flat. The toe, or low exposure end, of all films has a lower contrast than the body of the curve. Films are generally classified as being one of three types: long toe, medium toe, and short toe. Most general purpose films are medium toe. This is partly to insure that small exposure errors don't completely eliminate shadow detail. However, the effect of the toe is to lower contrast of the shadows. For a medium toe film with a fairly long straight line section increasing exposure to move the minimum exposure up the toe to a higher contrast section will often result in improved rendition. Short toe films have fairly high shadow contrast which is not much increased by increase in exposure. Short toes also tend to compensate for lens flare, the main effect of which is to decrease shadow contrast. There are a few very long toe films. Currently the only one I know of is Kodak Tri-X ISO-320 which is available as sheet film in 120 rolls. Note that the ISO-400 version of Tri-X is a medium-toe general purpose film. The ISO-320 version has a curve which is upward deflected at all points. That means that the contrast increses steadily with density and there is virtually no straight line portion of the curve. This film was designed mainly for studio work where there is little flare. The idea was to produce images with bright highlights. If one compares the curves for this film with a short toe, long straight line film like 100T-Max or 400T-Max you will find that if the shadow and highlight density points are matched, and both films are processed to the same contrast index, the mid-gray densities of the long toe film will be lower than the straight line film resulting in a darker rendition of these tones on the print. Such rendition can yield quite dramatic pictures of certain subjects, for instance of seascapes with foaming waves or skys with cloud patterns. It also can be used to exagerate skin textures in portraiture. The curve shape and grain both affect the image but are different things. A factor which is related to grain is the "smoothness" of tone reproduction. Finer grain films, and larger negatives, tend to produce "smoother" tone rendition. This is a characteristic easy to see but hard to describe. If what you want is smooth tone rendition the way to get it is to use the slowest film you can and to make the largest negatives you can (of course up to a limit). For size, the largest gain is going from 35mm to anything larger. Even 4.5x6cm shows a definite improvement in smoothness. Once you are at about 6x6cm the gain is relatively little for larger negatives. To my eye there is a lack of smoothness in 35mm pictures. I have been able to get something like this quality by using 100T-Max in Perceptol or Microdol-X (they are identical). This combination gives negatives nearly as fine grain as the late, lamented, Technical Pan in Technidol developer, not quite but pretty close, and with considerably more speed and much less fussiness. If you _want_ grain you must use relatively fast films and developers which do not tend to suppress grain, Rodinal being a good example. However, again, grain is mostly built-into the film and very fine grain films will still be fine grain even in Rodinal. There is a great deal more to this and I have written too much already. I've also over simplified a lot but I am trying to make some rather confusing concepts clear. Maybe not the best thing to try early in the morning. I probably should have just asked what sort of images you want to accomplish.Janet--- Richard Knoppow Los Angeles, CA, USA dickburk@xxxxxxxxxxxxx====================================================================== ======================================= To unsubscribe from this list, go to www.freelists.org and logon to your account (the same e-mail address and password you set-up when you subscribed,) and unsubscribe from there.
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