No prints, no scanning, just projection. Is it better to shoot at ISO 40 or ISO 50.

Note that I expose Kodachrome 25 at ISO 25 if that helps.

TIA, Bud

-- Bud (budcook@attglobal.net), August 04, 2001

Answers

There are several variables to your question. The type of screen you use, the distance from the projector to the screen and the darkness level of the room can effect the "apparent" brightness and contrast of the image on the screen.

I am like you, I don't do digital or print from slides (usually), so after much experimentation I do the following. While I always over rated my slide film in the past, (Kodachrome 64 rated at ISO 80, Fujichrome 100 rated at ISO 125), I have found that I like Velvia rated at exactly ISO 50. I read that many shooters use ISO 40, so I recon that my using ISO 50 gives me the slight under exposure that I like from the other emulsions that I used in the past.

I would advise that you go out and shoot some actual photos, bracketing through ISO 40, 50 and 64, and then pick out which shots suits your taste. If you make up a few pieces of poster board with the ISO values, and have them within the scene, it will be easy to pick the best ones out of the group. For the price of a single roll of film, you can have the answer that you need without anyone else's opinion over shadowing what would work best for you.

-- Al Smith (smith58@msn.com), August 04, 2001.

Thanks Al, As I said, I prefer Kodachrome at ISO 25(used to use 32 but changed when I got cameras with accurate spot meters).

I'm about to order more K25 from B&H for the freezer but I've got a roll of Velvia so I thought I'd give it a try.

I only asked the question out of curiosity. Some people like ISO 40 and some like 50. I wonder if it just depends on what the final medium is going to be. Of course it could be that people who use Velvia are so into over-the-top color that ISO 50 would just add to the thrill:-)

Regards, Bud

-- Bud Cook (budcook@attglobal.net), August 04, 2001.

When I was shooting for the car magazines, they hated the stuff done with Velvia at 50 for publication. When I bracketed, the editor always chose the slide exposed at 1/3 to 2/3 overexposed (ISO 32 or 40), so I ended setting the speed there and forgot the bracketing.

-- Andrew Schank (aschank@flash.net), August 04, 2001.

I shoot RVP at 40 in 35mm and LF. For some reason, in the past there did seem to be a speed "float" of about 1/3 stop between emulsion batches, so I did have some older batches of 35mm Velvia perform better at 32. I have not recently experienced this problem, however and normally rate the film at 40. It is probably a good idea to shoot a test roll at both 32 and 40 ISO settings to determine which you prefer for projection.

-- Jack Flesher (jbflesher@msn.com), August 04, 2001.

Oh yeah, I forgot to add that in agreement with Andrew, whenever I bracket the 40 rating I only bracket +1/3. I used to bracket both up and down 1/3, but I NEVER used the -1/3 (ISO 50) shots, only the +1/3 (ISO 32) shots, so now I only bracket upwards 1/3.

-- Jack Flesher (jbflesher@msn.com), August 04, 2001.

I shoot Velvia @ EI40 in partial sunlight because it tones down the color saturation and reduces the contrast. In flat, mid-day full sun (watching my composition for contrasts)as well as in overcast light, I shoot it at 50. Similar to others, I also rate my ISO 100 transparency film at 125 under the same conditions. I should mention that while I've found (maybe just lucky) that all the meters in my Leicas (R and M) agree, I have tested the mechanical shutters and know which bodies need to be compensated additionally at certain speeds where the true speed is closer to 1/3-stop from the marked one.

-- Jay (infinitydt@aol.com), August 04, 2001.

In my R4, I shoot Velvia at 40. If shot at 50, it has that super- saturated and slightly underexposed look that is not unlike Provia 100 when shot at 125. In the M6 or the Nikons, however, Velvia is fine at ISO 50, without corrections. Velvia seems to tolerate a small increase in exposure, of 1/3 or 1/2 stop, without obvious overexposure. So when in doubt, such as maybe working with an unfamiliar camera, it can be a good idea to set the camera to 40. Many people seem to feel that Velvia's ISO 50 is overrated. If I'd never shot it with anything but my R4, I'd think so too. But overall, I rate it at 50 unless there's a specific reason to do otherwise.

-- Bob Fleischman (RFXMAIL@prodigy.net), August 04, 2001.

Well known LUGger Henning Wulff had this to say about the subject...

"Kodachrome, as well as Kodak's E6 films, tends to have a longer 'toe' than films from Fuji, especially Velvia, meaning that shadow areas are separated better. Fuji films tend more to the 'black hole' syndrome, where anything below a certain luminance level tends to be completely black. On the other hand, Fuji films, (especially Velvia again) tend to have a longer 'shoulder' than Kodachrome, meaning that highlights are differentiated better. The overall result of these two factors is that Velvia in practice is better rated at 40, so that you get enough shadow detail, and overexposure is not as likely because of the long shoulder. Kodachrome 25, on the other hand, with its long 'toe', and shorter 'shoulder', is more easily overexposed and less likely to be underexposed, so can be rated at 32. This means that effectively Kodachrome 25 is only 1/3 stop slower than Velvia.

Their resolution is effectively similar, and both are for most purposes grainless, but Kodachrome has higher acutance (edge contrast effect) which results in Ilfochrome prints _looking_ sharper when made from Kodachrome. Color rendition is a personal choice, and somewhat influenced by fashion. Advertising demands high decibel levels on TV and shouting colors in ads, so Velvia with its higher saturation wins in those areas, and I use it for that reason for most of my commercial work, but for my personal stuff I prefer Kodachrome 25's color rendition. Some colors on Velvia can look downright violent.

All the above comments about Velvia apply to some degree to all of Fuji's 100 speed films,..."

-- Bud (budcook@attglobal.net), August 04, 2001.

There are several variables to your question. The type of screen you use, the distance from the projector to the screen and the darkness level of the room can effect the "apparent" brightness and contrast of the image on the screen.

One other variable is who develops it. There is more than a 1/3 stop variation in the result from a single lab.

Do my own Ektachrome. I have my prefered ISO for my own work.

Art

-- Art (AKarr90975@aol.com), August 04, 2001.

You've gotten several good answers to a tough question. Your metering and exposure techniques are certainly essential in the process. For me, I like to underexpose chrome a little when I project it. However, I project to a large 80" screen and the added saturation goes further. You really need a bright bulb and an excellent lens to do this. I use a Kodak Carosel 4600 and the excellent Kodak Ektapro Select 93mm f/2.5 German made lens. Can't say enough good about that lens, I suspect it is a Colorplan in disguise, just like the Leica RT projectors are Kodak's in disguise. Anyway, when you project to a large image, blown highlights really stand out and distract from an otherwise good image. Of course, underexposing means you lose shadow detail, but I'd rather lose that than have blown highlights and weaker colors, especially when the project image is large. So, my suggestion to you is, rate the Velvia at 50.

-- Dan Brown (brpatent@swbell.net), August 04, 2001.

It took me ages to figure out Velvia. I would agree with bits of previous answers...

1. It depends on the processing company you use and how you meter. The main thing is to be consistent with both before getting scientific with the performance aspects of the film.

2. My favourite UK landscape photographer Charlie Waite rates at 50 thats good enough for me.

3. I rate at 50 but it's worth noting that this rating does not give the same contrast / F stop latittude OVER and ABOVE the average reading. In other words if you take an average reading (ie. ambient)and rate the film at 50, then you may get acceptable detail in highlight at +2 stops (or so) but only get shadow detail at -1.5. I think that for the sake of colour saturation Fuji are actually asking you to under-expose by 1/3 stop when rating at 50. This is OK providing you know where you stand.

-- Tony Estcourt (tony.estcourt@talk21.com), August 08, 2001.