Exposing slide film
I'm having problems exposing slide film correctly. The only camera I've ever put it through is a fuji g617 and its getting expensive! I'm using a sekonic meter and taking ambient readings at ISO 32 loaded up with velvia 50, which takes into account the center filter. The conditions I was taking the shots in were very overcast. The shots which have turned out better exposed were the ones which I was expecting to be very overexposed by once accidentally forgetting to change the aperture and then by acidentally locking the cable release Is it time to get a spot meter and which one?
slide film only has 5 maybe 6 stops of range. Exposing at EI 32 gives 2/3 over exposure. But with a centre filter, if the filter factor is 1.6, then it should be almost correct.
So assuming you point your meter at the main light source, take a reading and then set that exact reading on camera, it should work more or less.
So how exactly are you metering and what is the filter factor for your centre filter?
The filtor factor is 2, so two thirds of a stop and I'm metering as I would for B+W negative, just holding the light meter up in front of the subject and taking an ambient reading. I was getting ok results before but for some reason this new lot are very dark. The ones I was expecting to be grossly overexposed are the ones which turned out ok.
On an overcast day, I would expect some degree of underexposure in general for the average scene. If you are getting overexposure, I wonder if your meter is well calibrated or if you are metering correctly.
When I shot slide film, I calibrated the film speed to the meter I was using based on tests with a gray card (Zone V). For me, Velvia came out the same as its rated speed of 50. I used a spot meter and exposed the most important part of the scene to the Zone I desired. I would check to make sure that the important shadows did not lie below Zone III and that the important highlight did not lie above Zone VI. If they did, my choices were to accept the fact, move on to another subject, use a graduated gray filter for the sky, perhaps use a polarizer, use a reflector to fill shadows or block highlights, etc. I did not resort to more heroic measures for contrast reduction.
if the filter factor is written as 2, then it means 2 times the exposure time so it's a one stop adjustment and not 2/3 stop. So EI 25 would be better.
If filter factor is written as 0.1 or 0.2 then it refers to density adjustment and not time and in that case each 0.1 equates to 1/3 stop. So 0.3 would 3/3 stop or 1 stop.
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RVP in overcast light
Velvia should respond very well in diffuse light (overcast/heavily overcast) best at EI40 or EI32. Not keen on taking a reflected reading from or near camera position especially near water (waterfalls, among); I think a spot meter should be employed across the scene to plot the exposure within the dynamic range of RVP (Velvia) before you shoot; this is less of a problem in diffuse light (RVP's design intention) than, for instance, point light, when RVP looks just awful and one then biases exposure in favour of highlights at the expense of shadow, if you must shoot in such conditions at all. Some light meters, like the Sekonic L758 I have, can be precisely calibrated to account for filter and lens factors during measurement.
The suggestion in another reply that a polariser could be used needs to be viewed with care: in very overcast light a POL can cause a very flat/muggy appearance despite obvious primary lifts (esp. green). I use a POL routinely in overcast light (for rainforests et al), meter calibrated +2/3 to 1 stop (RVP at IE40 to start) — then 1 bracket each side. I don't ever shoot RVP in bright to hazy sun (Provia 100F handles contrasty scenes so much better). So...invest in a fine spot meter with averaging/Ev function to find a middle ground and EXPERIMENT: costly and frustrating as it is, experience is a wonderful teacher.
.::Gary Rowan Higgins
One beautiful image is worth
a thousand hours of therapy.
"It is horrifying that we have to fight our own government
to save the environment."
When using slide film, it's normal to expose for the highlights. I take a highlight reading in reflective mode on my Gossen Lunasix, which I apply to the camera, and bracket if I'm uncertain. My exposures are usually sound, which has been my experience with Velvia 100F and Ektachrome 100 VS, two contrasty films.
Transparency films have less lattitude than negative films, and IIRC have more lattitude towards underexposure than that of over.
By all means buy a spotmeter. I get by quite nicely without one.
For you centre filter, as Rob says, double your exposure, so for a 50 ISO film, expose at 25 ISO.
You might test your camera thoroughly using a neg film in different exposure situations and an accurate, handheld meter. With neg films, meter for shadows as these films have more lattiude to overexposure. If you still get gross underexposure, your camera may have a fault. A qualified technician can check the shutter for accuracy.
I speak from experience.
only 4 exposures!
Originally Posted by dmr
As the factor being used was a 1/3 stop out and as the fish says, overexposing by a 1/3 or 2/3 stop is good for velvia, then that would account for a full stop under exposure which is 2 zones in zone speak. So with centre filter try at EI 12 or 16 and see how you go.