exposure and grain question

[todd_b1]

<p>Hi,<br>

<br />I'm trying to get a good understanding of the influence exposure to grain, here are two images from the same roll of film. This is Tri-X and Diafine. The Diafine data sheet says it pushes Tri-X to 1600 (!). The first was in full sun at a beach, I am sure f/16 and probably 1/500 or faster. The second was also in full sun but reflected from the water in the baby pool.<br>

<br />Can you help me understand what accounts for the difference in grain and look?<br>

Thanks,<br>

<br />Todd</p>

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<p><img src="http://farm8.staticflickr.com/7136/7451781974_e91125b07f_c_d.jpg" alt="image 1" /></p>

<hr />

<p><img src="http://farm8.staticflickr.com/7113/7451784078_56762174bb_c_d.jpg" alt="image 2" /></p>

[bruce_watson1]

<p><em>I'm trying to get a good understanding of the influence exposure to grain...</em></p>

<p>Easy. Graininess increases as density increases. That's why highlights from B&W negative film (that is, high density areas) are more grainy than shadows (low density areas). </p>

<p>It's the formation of metallic silver film grains that causes the density in B&W negative films. As the film grains meet and overlap (the emulsion is a 3D space so there is plenty of overlapping of grains near the surface of the emulsion with those lower down in the emulsion) they form "grain clumps" which are typically what you are seeing when you are seeing lots of graininess.<br>

<em> </em><br>

Exposing and processing B&W films is an art. You need just enough exposure to register your shadows, and just enough processing to give you the minimum density in the highlights that lets you print well (either darkroom printing or scanning, although optimum density for printing will vary depending on the process used).</p>

[todd_b1]

<p>Many thanks Bruce, you could not have made this clearer. A whole new world of things for me to think about. I need another lifetime to master :). I like the look of the beach photo, but this is just the way it "turned out", no control exercised on my part. In this situation, if I were going for a more realistic look I should have underexposed (less density) and then compensated during development? I don't Diafine gives me any control there. Is there a rough feel for the number of stops I should have underexposed? And then using a one-part developer I could compensate?</p>

[larrydressler]

<p>I rate Tri-X at 1250 in Diafine.</p>

[JDMvW]

<p>That top one doesn't look like grain to me, it looks like reticulation (for how to purposely do it see http://www.ephotozine.com/article/create-reticulation-when-film-processing-4639 ). Did temperature get out of control one way or the other in the processing?</p>

<p>On the other hand, I did once get wildly differing grain on the same roll one time with some 10-year old film. The other roll processed at the same time in the same tank was all ok.</p>

[lex_jenkins]

<p>I'm seeing some obvious scanning artifacts in the beach photo - note the squarish repeated pattern. That may be exaggerated by JPEG compression as well. </p>

<p>You'd get better results with conventional enlargement. Tri-X in Diafine is a terrific combination for some situations, but it's not the best choice for scanning of negatives. My 8x10 and larger darkroom prints from 35mm Tri-X in Diafine are grainy, but not nearly as grainy as your beach photo.</p>

<p>As Larry suggested, try rating Tri-X at 1200-1250 for Diafine. Seems like an insignificant difference from the manufacturer's suggested 1600, but it does make a visible improvement.</p>

<p>For the sake of curiosity, try bracketing some identical shots as well, as if you're rating Tri-X at EI 200, 320, 400, 640, 800, 1200, 1600, 3200, etc., on the same roll, for developing in Diafine. If your experience is anything like mine you'll see some really odd looking results at EI 200-800. Diafine has a fairly narrow sweet spot for exposure with some films. I did these bracketing tests with Tri-X, FP4+, Delta 3200, TMX and TMY to determine my own personal EIs for each.</p>

[Alan Marcus]

<p>The size of the grain in photo films is basically set during manufacture. As a general rule, fast films (higher sensitivity) exhibit larger grain structure. This is true because the makeup of faster films is to use larger crystals of light sensitive salts of silver. The larger the crystals the higher the probability they will be hit by photons and rendered developable.</p>

<p>When a crystal is exposed and developed, a tiny fake of metallic silver becomes imbedded in the film emulsion. These flakes are far too tiny (microscopic) to be seen as grain, however the grain we see and hate is a clumping together of adjacent flakes.</p>

<p>The best way to avoid horrid grain is to use low speed film. Since slow films are not always practical, we resort to using developer formulas that moderate the grain. Generally, these formulas contain a mild silver solvent that works to whittle down the size of the metallic flake. The temperature of the process also plays a key role. I am talking about the temperature of all fluids that contact the film. The flakes of metallic silver are somewhat mobile in the gelatin binder we call the emulsion. Too high a temperature causes these flakes to "dance" and aggregate. Temperature differences from bath to bath cause abnormal swelling of the gelatin and this promotes clumping.</p>

<p>Grain is present in all photographic images. Because it is a random distribution, it becomes more visible and thus more objectionable in mundane areas like cloudless sky etc. Prolonged developing time promotes graininess. Underexposed areas reveal little detail thus they are uniform in tone (mundane) and demonstrate more granularity. </p>

<p>In other words, granularity in films is a complex subject and I am known to output gobbledygook.</p>

[todd_b1]

<p>Many thanks all. JDM, I don't think temperature is an issue, the Diafine sheet says 70-85 degrees (huge window!) and I am right at 75, and I would think this would impact the entire roll, not just a few frames. Here is another image for an extreme example. Cloudless sky as Alan notes. I like the look but would like to be able to control it. Diafine doesn't give me the ability to prolong (or not) development, it kind of does what it does so perhaps I should try switching to another developer. But I'm not really sure what steps I would take for a beach scene like this if I wanted emphasize the plane. I use a yellow filter for what it's worth. Lex, I will try for sure to bracket shots across EI to see what this gives me (if interested to anyone I can post it). 1600 vs 1200 is less than a full stop, forgive me if I sound completely ignorant (I am), but can I just eyeball this, say one third of the way between two apertures? Just to be sure I looked at the negative with a loupe to confirm the scan is reproducing (more or less) the grain correctly.<br>

Thanks all, help is really appreciated, basic stuff but new for me.</p>

<hr />

<p><img src="http://farm8.staticflickr.com/7260/7451780696_6633ac97d2_z_d.jpg" alt="image3" /></p>

[JDMvW]

<p>All this discussion about grain is very nice and all that, but I repeat, your examples look like <strong>reticulation</strong>, not grain.</p>

<p>This is harder to do with modern films, but can also occur, for example, <em>by a strongly acid fixer following a highly alkaline developer, or other shocks to the film coating that cause it to "wrinkle." </em>Temperature differences are only one way to get there.<em><br /></em></p>

<p>Reticulation also would explain how different parts of the same roll could be so different - depends on what was hit by what...</p>

[larrydressler]

<p>Diafine is my specialty developer. I use different developers for different jobs and films. Diafine is nice for some things but not all. If there is going to be a lot of open area like sky I prefer Xtol or HC-110 for Tri-X. But I do have to say that last one looks like more than just Tri-X grain.</p>

[lex_jenkins]

<p>Reticulation might occur if there's a drastic difference in temperature between the developer and wash - sometimes this can occur when using running tap water without checking it. But the artifacts I'm seeing resemble scanning and JPEG artifacts more than reticulation. There's also some exaggerated grain, but that's also typical of scanning. It probably wouldn't be so obvious in conventional enlargements.</p>

<p>There's also some uneven development in the frame with the airplane. Diafine can be tricky to master, especially with plastic reels - surge marks and uneven development can sometimes occur.</p>

<p>Tri-X in Diafine is a good combination, worth the effort to get the hang of.</p>

[todd_b1]

<p>I think my next task is to shoot more film and experiment! And pay much closer attention to temperature. Now that I think about it the fixer had been freshly mixed and would not have been at the same temperature as the developer -- I usually take this for granted because they have been sitting on the same shelf. I did not know about reticulation. Many many thanks! I like the look so one mission will be to reproduce this on demand.</p>

[JDMvW]

<p>I still say, that "wormy" look is a wrinkled emulsion, not jpeg or other digital effects. I'll shut up if the film itself doesn't show the effect. This is one of the most classic examples of reticulation I've seen, IMHO.</p>

<p>The link I gave shows methods for getting reticulation, and a Google™ search yields more sites at a glance that are about making reticulation than preventing it. <br /> I did find one source that had a technique which sometimes worked in fixing already reticulated film. It involved resoaking and some other things, but I'm sorry but I lost the link... :|</p>

[todd_b1]

<p>I am happy to say reticulation all the way. Interesting it can happen only on some places within a roll. I split a roll today and am doing some tests, for fun. I am going to be very very careful with temperature, take some open sky photos across a broad range of EV, and then develop in both Diafine and Tmax. Will post a follow-up if anything interesting!</p>

[mjferron]

<p>Under exposure and over development can lead to exaggerated grain. I always get finer grain pulling the film and cutting the development times no matter what combo I use.</p>

[larrydressler]

<p>Yes Pulling film will reduce grain in almost any developer. But as I said and others that is just not grain. Diafine is wicked with most films as it just allows development to completion so it is said but even some need 3+3 some 4+4 others 5+5 and yes you can make changes with 3+1 and so on with some films. Learn your film . Learn your developer and most of all learn the limits and exceed the average.<br>

Temperature even with Diafine is needed Many never notice it is better above 20C and 20C is not recommended. I have had a devil of a time this summer with water temp for washing so I went to a hardening fixer.<br>

Larry</p>

[michael_madio]

<p>The "wormy" artifacts look like what I get with the scanner grain reduction on very dense areas of film. The best way I found to deal with this is to disable any auto-correction features such as grain reduction, scan at the highest optical resolution, then down-sample by 50% (e.g. scan at 4000dpi then down-res to 2000dpi).</p>

[diego_lyon]

<p>Hi there,<br />Not sure if this thread is still alive, since it's been over 4 years hahaha, but I'm exactly on the same topic and I don't quite understand why this happens. I'm using HC-110 (Dil. B) instead of Diafine, and developing all film at its original rating, following the specified times. Temp for both developer and fixer is 20ºC (68 F), and my washing is a little above since I use tap water, so around 22-23ºC. I do a water stop bath and use Ilfotol at the end.</p>

<p>These are a couple examples from the same T-Max 400 roll, but with very different grain (sharpness?): Why does this happen?</p><div></div>