Exposing slide film

Discussion in 'Color: Film, Paper, and Chemistry' started by Jarvman, Jul 14, 2008.

  1. Jarvman

    Jarvman Member

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    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 :confused: Is it time to get a spot meter and which one?
     
  2. RobC

    RobC Member

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    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?
     
  3. Jarvman

    Jarvman Member

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    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.
     
  4. jeroldharter

    jeroldharter Member

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    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.
     
  5. RobC

    RobC Member

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    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.
     
  6. Poisson Du Jour

    Poisson Du Jour Member

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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. :smile:
     
  7. kevs

    kevs Member

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    Hi Jarvman,

    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.
     
  8. dmr

    dmr Member

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    Bracket!

    I speak from experience. :smile:
     
  9. Jarvman

    Jarvman Member

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    only 4 exposures!
     
  10. RobC

    RobC Member

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    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.
     
  11. Jarvman

    Jarvman Member

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    Is it worth using a digi slr *hiss* to get a representation of the exposure or will there be a difference?
     
  12. Rich Ullsmith

    Rich Ullsmith Subscriber

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    I would talk to the lab first, ask what they are doing. Some of these places, like the local one here, seems like a new employee every time and if you start talking about pushing and pulling and filter factors, they don't have a clue. Chemistry gets old, too. It sounds like you have thought things out to a reasonable degree on your end, so I would ask them about it.

    Using a digicam as a kick-butt light meter might seem like a good idea, but until you spend some serious money, the light meters in are really among the weakest link in gettting a great exposure. It won't necessarily extrapolate to your film.
     
  13. RobC

    RobC Member

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    The light meter in a digi slr will be as good as any other in camera lightmeter but the big difference is that the digi slr will have an acceptable contrast range. Maybe 10 stops or more. Slide film (positives, chromes) is high contrast film and only accepts 5-6 stops depending on which film. Some maybe a little more.
    So whilst with a low contrast subject a digi camera may show the subject as flat, the Velvia may show it as just right or quite contrasty. There is no direct comparison as a digi equates to medium to low contrast film whereas as slide is high contrast. Electronics may fiddle with that but you have to know exactly how your camera works to be sure of that.
    If you are a zone system person, then you will know that there are 11 zones. 0 thru 10 and each zone is one stop. With slide film which only has a range of 5 stops you can make each zone 1/2 a stop. Because slide film is so high contrast, a small change in exposure makes a big difference. Infact about twice as much difference as on black and white film.

    Read what poisson du jour said carefully.
     
  14. Poisson Du Jour

    Poisson Du Jour Member

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    I agree wholly with rob champagne. Many digi photographers take the image on the external LCD as gospel, which in fact is the wrong (or lazy) approach. That display only gives an indication of the dynamic range of the sensor and where the image being framed fits into it. It bears no relationship at all to real-world metering with transparency film which, as rob points out, has a perilously narrow latitude. If you photograph a waterfall with a digi, there is a very good chance of highlights in the water clipping. With tranny film (notably Velvia), this clipping is much more graceful and subdued. I wouldn't personally trust a digi meter no matter how sophisticated or accurate it is touted.


    Lastly, be aware that in digital cameras that image is nothing more than a complex mathematical interpolation of three primary colour channels. With film, the image is captured direct to the medium in a way that has remained fundamentally unchanged for more than a century. I sitll prefer either my EOS 1N's meter, my Sekonic L758 with a contracted Zone System (11 zones to 5 in 0.5 as rob points out) or a 'guesstimate' i.e. "f8 and Be There!"