Reciprocity Failure table for FP4 & HP5

<p>Hey there. this is my second year with film at college and im now pushing to use a large format Camera (5x4) after speaking to my tutor he said i need to take reciprocity failure into account and to find a table online wich i cant find anywhere.<br>

so my question is - <br>

Is there a spreadsheet out there with times worked out and would it differ indoors to outdoors. the idea is to photograph VERY long exposure night shots.<br>

Please help.<br>

p.s sorry if this is posted somewere else i couldnt find it </p>

<p><a href="http://www.ilfordphoto.com/Webfiles/2007321132461251.pdf">HP5+ Fact Sheet</a> (in PDF format).<br>

Others can be found on Ilford's website: http://www.ilfordphoto.com/products/default.asp</p>

<p>First, you need to understand what <a href="http://en.wikipedia.org/wiki/Reciprocity_failure#Reciprocity_failure">reciprocity failure</a> actually means. What it means is that some or all parts of the film are not receiving sufficient photons to make a reliable latent image. This has been a problem since Niepce's invention in 1826. As such, it's been an object of continuous improvement over the years.</p>

<p>Clearly, some films do better with low light exposures than others. Every film has different reciprocity characteristics, and these characteristics tend to be non-linear. Manufacturers have more or less given up on publishing reciprocity formulas and tables. The standard advice is to test, test, test. Learn from your tests and use that knowledge in your work.</p>

<p>Some things for you to think about. First, modern emulsions do better with reciprocity failure than older emulsions. This shouldn't be a big surprise. The current leader seems to be Acros, then Tmax (100 is slightly better than 400), then Delta. Any of these films have considerably better low light performance than FP4 and especially HP5.</p>

<p>Second, reciprocity failure seldom effects the entire negative. A night street scene with a street light is a good example. The part of the negative with the street light will get sufficient photons to make a good exposure while the darkest shadows will not. But since you can only process the whole negative at once, you end up with a very contrasty negative as a result. This can make for a difficult time darkroom printing, and scanning. This is why people will often advise pull processing negatives such as this -- to decrease the highlight density. Remember: expose for the shadows and develop for the highlights.</p>

<p>About reciprocity:</p>

<p>The law of Reciprocity E=IT<br /> Exposure is the product of the Intensity of the light multiplied by the Time light is allowed to play on the film.</p>

<p>Reciprocity is good!<br /> This law tells us that if a good exposure is obtained at f/8 at 1/50 second - then a good exposure can be obtained at f/11 at 1/25 second or at f/5.6 at 1/100 second etc.</p>

<p>What we are talking about is the amount of light energy needed to expose film. Now film is subject to inertia, a tendency to remain at rest. Thus, when the shutter opens and the film is bombarded with photons, the ISO (film speed) allows us to predict how many photon hits will be required. Now the ISO value applies only to the normal (moderate) shutter speeds range, which is about 1/10 of a second to 1/1000 second. In other words, the ISO value is only valid over the usual exposure time span. Should the exposure be quite lengthy, the photon hits will be spread out over time, this allows some 'healing” to transpire between hits. In other words, the light sensitive chemicals of the film recover somewhat between photon hits so additional hits will be required to do the job. At lengthen exposure times, the ISO must be revised o provide more exposing energy. This phenomenon is called Reciprocity Failure.</p>

<p>Conversely, if the shutter speed is abnormally fast, say 1/1000 second or quicker, the photon hits happen in quick succession, the full impact of each hit is not transmitted before the next hit occurs. The net effect is, more exposing energy is required when the exposure time is very quick. This phenomenon is also called Reciprocity Failure</p>

<p>Stated another way: The ISO of films plummet at very long and very short exposure time.</p>

<p>Sidebar: In astrophotography, exposures typically can be hours, long and films exhibit a severe ISO drop. Astronomers have discovered that super cold film is virtually immune to reciprocity failure. Astronomers typically use a cold camera. The film back of the film hold dry ice and this cools the film during exposure. A second common countermeasure is to pre-bake the film in a special oven filled with a recipe of unique gases. The baked gassed film is highly resistant to reciprocity failure.</p>

<p>More gobbledygook from Alan Marcus</p>

<p>I compensate as follows:<br>

<br /> Metered exposure time, RF increase, Development factor<br>

<br /> 1-5 secs, 0.5 stop, 0.85<br /> 6-10 secs, 1 stop, 0.67<br /> 11- 20 secs, 1.5 stops, 0.55<br /> 21-40 secs, 2 stops, 0.45<br /> 41-80 secs, 2.5 stops, 0.40<br /> +80 secs, 3 stops, 0.35</p>

<p>So, if you meter your scene and the exposure time comes out as, say, 35 seconds, you add 2 stops, i.e. double and double again, giving you 140 seconds actual exposure time. Then you cut your development time to 0.45 of the base dev time, so if the dev time should have been, say, 10 minutes, you cut it to 4.5 minutes. In this case, I would increase the developer dilution to give a longer time - 4.5 minutes is too short for my liking.</p>

<p>Here's an example using the above. Note that I metered off a Zone III, which gave me a base exposure time of 30 seconds. I use that to calculate the RF compensation. So, this was shot on FP4, rated at 50 ASA, f/22, 30 seconds and devved in Rodinal 1/100, 20 C, 8 minutes.<br /> I'd better clarify here. My Zone III reading gave me an exposure time of 30 seconds. Moving the raw reading down to Zone III gives an exposure time of 7.5 seconds, but adding in 2 stops of RF compensation takes me back to 30 seconds. (That was just a coincidence.)<br /> The dev time in Rodinal at 1/50 would have been 4 minutes so I doubled the dilution and the time.</p><div></div>

<p>I'd tend to agree with Bruce's observations. In my experience with long exposure nighttime photos, reciprocity tables don't quite account for every scenario. Very contrasty scenes such as nighttime photos under moonlight or sparse streetlights can be tricky.</p>

<p>I tend to guesstimate, based on experience with a few familiar films, and use compensating developers to balance out the contrast. Admittedly, even the concept of compensating developing is subject to some skepticism. But I've had good luck with Diafine used normally and with stand processing in very dilute Rodinal.</p>

<p>The rest is down to manipulations during enlarging or digital editing.</p>

<p>Long exposure nighttime photos under moonlight:<br>

<a href="../photodb/folder?folder_id=319616">FP4+ in Diafine</a><br>

<a href="../photo/1748403">Tri-X in Rodinal 1+200</a></p>

<p>Guys thanks for the Info it is helping. im just a bit of an idiot with Film. i started using it last year for the first time and fell in love with it. so im learning slowly but surely.<br>

im restricted to FP4 and ID-11 any tips for help with these wich will affect reciprocity Failure?</p>

<p><em>...I'm restricted to FP4 and ID-11 any tips for help with these which will affect reciprocity failure?</em></p>

<p>Well, I can at least give you something to look for. When I was using a lot of 5x4 Tri-X, most of what I was doing was landscape. I was in particular drawn to wide dynamic range scenes with lots of shadow detail. For example, rocks in a river in full sunlight. I spent an inordinate amount of time trying to get those shadows right without blowing the highlights all over. More often than not I got satisfactory results, but it still seemed lacking somehow, so I kept after it.</p>

<p>Then one day for no particular reason other than the egging on of friends, I bought a box of TMY (when it first came out). Made a trip to a favorite area of a local park. It's an old mill site. Made some photographs of the remaining part of the damn. I couldn't believe the high quality of the shadow detail where the rocks were fitted together, and some tree shadows. Very linear. So I scratched my head and thought about it and of course continued making photographs. Eventually I revisited a site in the mountains that I'd struggled with and tried again. Couldn't believe the results. The shadows under the rocks in the stream were spot on and very linear. This was what I'd been trying to achieve for years.</p>

<p>It finally dawned on my why I could do so well with TMY with seemingly not much effort (but a fair amount of experience by that point), but struggled so with Tri-X. It was because that 1/8 second exposure with Tri-X was putting the shadows into reciprocity failure. That same 1/8 second exposure with TMY was not. So the density of the TMY negative was linear in the shadows, where with the Tri-X it was not.</p>

<p>To test my theory I did just what you'd expect. Shot a bunch of different scenes with both films using the same shutter speed (I actually found TMY to be about 1/3 stop faster with my workflow, so the TMY in my experiment actually got 1/3 stop less exposure). Put the two sheets side-by-side on a light table, then it was plain as day what was going on -- you could see it from the other side of the room! Well, without using a loupe anyway. ;-)</p>

<p>Moral of the story? You're going to struggle more with FP4 and HP5 than you would using a better film for the duty, like Acros, Tmax, or Delta. Sorry, just the way it is. But at least now you'll know what to look for.</p>

<p>All you can do if this happens to you (assuming you won't change film or developer) is expose for the shadows and develop for the highlights. That's really all the controls you have to fight this. And it's going to be a fight. But, you'll be able to win it if you are persistent, keep good records, and maintain a very repeatable workflow. You'll be working on the edge, and sometimes you'll step off on one side or the other. Almost always when it's a shot you really care about. :-( But it's doable.</p>