Whatever you decide, please post the results.
I did a 20 minute exposure, which I felt was a long time, of people watching a movie that was being projected on the side of a parking garage. I was on the parking garage and had a great vantage point. With a subject like that though, many people stood still for 20 minutes (some people stood surprisingly still).
I've done some hours exposure with Reala, K1000 and the 50mm SMC with the North Star. It works out pretty good.
What I'm going for will be a difficult thing to catch, for sure. It will be in color. I'm not looking to have the people show up at all except for what they show up incidentally with the lights they will be carrying. The people will be 1000-2000 feet away, to add to the difficulty in capturing them, but they will be following the same path so hopefully they will show up in aggregate. The landscape around will be illuminated by moonlight, so I have to be careful with the phase of the moon so as not to overexpose over that period. I'm looking for people trails the same way you look for star trails. There will also be star trails in the shot, for sure. I am going to do some testing for sure. It will be more than 6 months from now when I actually attempt to capture what I'm going to be capturing, depending on weather and a number of other factors, but I need to start testing now to maximize the chances of success.
I've probably 30-40 different star trail shots up to 1 hour in exposure length usually using Provia 400F with fantastic results, but I'm weary of a 4 hour exposure with film that fast, so I'm thinking Provia 100 to start with. There's not a ton of films available in 4x5 it seems.
Does Velvia 100 go green like it's 50 cousin? There also seems to be Ekatchrome 100G. Anyone ever use that? I've never tried color negative film for long exposures. Does it work well? I've always loved the color rendition of transparency film.
I want to capture it on film with one or more 4x5 cameras. I'm going to need a lot of luck.
This project has a lot of challenges.
- Film for 4 hour exposures
- Phase of the moon that won't overexpose the landscape
- Lanterns or lights that will show up like star trails from 1000 to 2000 feet away at walking pace
- Finding people crazy enough to do what I want them to do in the dark and in the wilderness
- Incredible luck with weather
Weather alone can delay this by an entire year, so I will need all the luck I can get! My head is spinning with ideas though so if I can't do the one shot I have in mind this year (I'll attempt it the next) perhaps I can come up with similar ideas at less remote locations and work out all the bugs. We'll see. I'm not going to reveal what or where exactly this picture will take place. That will be a surprise.
Velvia 100 is my favorite film for moonlight, unless I want Provia 400x for more speed. I have not had the green shift 50 sometimes gives (though I'll say that I strongly prefer 50 for almost every other application). I have only done exposures up to the 4 to 5 minute range. Under a full moon on green grass, 3 minutes at f4 is my usual starting point. As expected, Velvia 100 results in more saturated colors (especially reds and browns) than Provia.
Originally Posted by kurt765
Velvia 100F is not bad either, but it's skies are more cyan than 100's, and I prefer a deeper blue.
Sorry for the late response. I don't have the luxury of a densitometer, and I only rarely shot Acros 100 and TMax 400 when I did this test, so negatives were actually a bit underdeveloped for the TMax 400 and a bit overdeveloped for the Acros 100. I have tried to follow manufacturers instructions.
Originally Posted by Early Riser
I have been looking at the entire tonal range, and what I saw was consistently slightly more shadow detail for TMax 400 in all negatives up to 8 hours, and less contrast than in Acros 100. This last point may be effect of the development as per above.
Please do note though that for all real exposure times I tested (7.5, 15 and 30 minutes, 2, 4 and 8 hours) TMax 400 and Acros 100 were very close, although Acros 100 was maybe more close to TXP 320 for exposure up to 2 hours. In fact, if I had seen the negatives, and didn't know what they were, I might have assumed they both had the same ISO speed, just received a different development...
I am not at all disputing the fact that higher ISO speed films generally loose speed faster than low ISO speed films. This is a well documented phenomenon.
Originally Posted by Early Riser
The thing I am disputing is the general "myth" that for very long exposures times, 100 ISO films will be "faster" than 400 ISO films and you will thus have shorter exposure times with 100 ISO films, regardless of what 400 ISO film you are shooting.
While the "myth" may be true for a film like Ilford HP5, some films, even in the 400 ISO range, just have far better reciprocity failure characteristics than others, and I am especially referring here to TMax 400. As a consequence, the break even point between 100 and 400 ISO speed film may not be reached within any realistic exposure time scenario. This is the case for TMax 400 against any 100 ISO film like TMax 100, 125 PX, Fomapan 100 or so. TMax 400 will beat these films at exposure times up to 8 hours... Again, Acros 100 is the big exception, as it almost equals TMax 400.
To illustrate this also, I included Ralph Lambrecht's Reciprocity failure correction table for TMax 100, TMax 400 and "Conventional film". I think you will agree with me there are few people on this globe who have done more rigorous testing than he did. You can find this table and others on his webpage. See the link to the PDF document of the "Reciprocity Compensation" table there.
Let's assume you have set your light meter set to 100 ISO, and get a measured or indicated time of 15 minutes, the maximum measured time Ralph included in his table. Look at the table, and see how Ralph indicates an adjusted time of 40 minutes for TMax 100 to get correct exposure.
Now a measured time of 15 minutes at 100 ISO, corresponds to a measured time of 4 minutes at an ISO 400 setting of the light meter. Looking up the adjusted time for TMax 400 for 4 minutes, results in an adjusted time of 14 minutes.
So, in exactly the same light circumstances, shooting the same scene, TMax 100 requires a 40 minute exposure, and TMax 400 just 14 minutes...
Even the "Conventional film" column, which I found quite accurate for HP5, still has a shorter exposure time listed at 30 minutes, than TMax 100. Of course, with measured exposure times rising above 15 minutes (not in Ralph's table), the conventional film (e.g. HP5) is likely to quickly loose out against TMax 100, but TMax 400 won't.
Looking at my negatives and the data provided by manufacturers, I have the feeling there are two big exceptions in the field of reciprocity: TMax 400 and Acros 100. Both excel at long exposures, loosing relatively little speed and needing the least reciprocity failure correction of all films in their speed range. In fact, as said above, Acros 100 is so good that it almost matches TMax 400 at long exposure times, although maybe more close to TXP 320 at exposures up to 2 hours, a film which did quite well too. Whatever the exact situation, using Ralph's adjusted time column for TMax 400 for Fuji Acros 100, should get you in the ballpark for a correct exposure for Acros 100 too.
No arguing about that ;), if you need the extra quality, go for the 100 ISO film, and preferably Acros 100 if you don't want to be out to long in the dark cold night. However, I more and more find myself shooting 4x5, where 400 ISO is no issue.
Originally Posted by Early Riser
To illustrate my point in another way, and using Ralph Lambrecht's table I posted above and your E.I. (Exposured Index) reasoning, looking at the 15 minutes measured or indicated time (which is close to the 1000 seconds / 17 minutes you indicated from the Fuji film datasheets), results in an adjusted time of 1h 10 min for TMax 400 as listed in Ralph's table.
Originally Posted by Early Riser
This is about a 2 1/3 stop speed loss, meaning TMax 400 acts as an EI 80 film or so at 1000 seconds measured time. That is still 2/3 of a stop faster than the corrected EI 50 you calculated for Acros 100 at 1000 second measured time, and means the "break-even" point between the two films is not yet reached.
The basic point here is that, although the 400 ISO TMax 400 loses speed slightly faster than Acros 100, it starts out with a 2 stop advantage, which is a considerable advantage.
In addition, Ralph's tables seem to indicate that speed loss levels off / stabilizes for TMax 400 too. Like you correctly reported, according to the Kodak film datasheet of TMax 400, a 100 seconds measured time needs a +1 1/2 stop correction. But the 1000 second measured exposure needs only a +2 1/3 stop correction. So although going from 100 to 1000 seconds (more than 3 stops), the extra speed loss that needs to be accounted for is only 2/3 of a stop...
Fuji T64 or Provia, cross processed if necessary to allow for some overexposure slop. I've done the same with T64 indoors at an event.
Are you sure about those LP/mm figures above? 50 for T-MAX 400 and 60 for Acros seems low, 150 and 160 seems more reasonable but I could be wrong. You need a very good lens to record 160 of course.
I did some tests with no moonlight over the weekend. I need to finish off the rolls to get the film developed. On my DSLR, just 45 minutes was enough to get detail in the landscape at ISO 400 at f/5.6. For the film I tested Velvia 100 and Provia 100, About 3.75 hours at 5.6 and also at f11. More testing will have to be done, particularly with moonlight levels.
Just to state what might be obvious: bracket...
As this is a probably non-repeatable event (I'm guessing the "perfect alignment" that will make time end, or whatever) that would mean several cameras. Beg, borrow, but don't steal, every Speed Graphic you can find, make a rack out of lumber, and line them up. Several films, several apertures, several lenses. Obviously, keep working on the testing and don't leave us in the dark!