Slides overexposure

Discussion in '35mm Cameras' started by dps, Aug 4, 2005.

  1. dps

    dps Guest

    Hi all,

    the guy I buy film from, suggested me to overexpose Velvia, by changing
    the ISO setting for Velvia 50 to ISO 40 and for 100 to 90. Any
    experiences? Does the same stand for sensia?

    Thanks a lot!!!

    dps, Aug 4, 2005
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  2. dps

    Justin Thyme Guest

    I've found that some processing doesn't seem to like Fuji films real well,
    and this can be compensated for by giving it 1/3 stop over-exposure. (BTW,
    you expose 100ISO at 80, not 90. Unlikely to find a camera that gives you 90
    as an option).
    One lab that I was sending Sensia to, I found I had to overexpose by setting
    it to 80. Kodak film however had to be exposed as per normal. When I first
    started developing myself, I also found that Sensia had to be set to 80 to
    get similar results that I got from Elitechrome at 100. I since found that a
    slight increase over recommended development time, and an increase in
    agitation has made up the difference, so I now expose at 100 again.
    Labs that used Fuji chemicals seemed to develop it properly when it was
    exposed at the normal setting. Presumably these labs would make a mess of
    Kodak, not sure.
    Sorry, I haven't used enough Velvia to be sure of it's behaviour.
    Justin Thyme, Aug 4, 2005
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  3. The difference between 50 and 40 is not too large, many people would not
    be able to notice the difference. The difference between 100 and 90 is very
    small and few people would be able to notice the difference, even with a
    side by side comparison. (It is about 1/3 of what most people can detect).

    I suggest that on your next roll, pick a couple of typical subjects and
    expose one each way (you might want to write down which is which) and then
    view the results and decide for yourself.
    Joseph Meehan, Aug 4, 2005
  4. dps

    dps Guest

    sorry about that mistake :-/

    I guess I'll have to play around more myself. One question though, do I
    tell the lab that the film is shot at, say, iso 80? Do I have to shoot
    the whole roll at iso 80? Or the lab should follow its usual procedure?


    dps, Aug 4, 2005
  5. dps

    Norm Dresner Guest

    I haven't used Velvia but for ALL of my Kodak slide films -- Kodachrome and
    the various varieties of Ektachrome -- in all formats I've ever used in the
    last 40 years (35mm, 6x6 and 6x9), I've always dropped the film speed by 1/3
    stop, like you say from ISO 64 to 50 or 100 to 80. The very slight
    additional density in the image more than compensates for any loss of shadow
    detail but increased detail in the highlights.
    BTW, print film is usually exposed the other way, increasing the ISO by 1/3
    stop to slightly overexpose the negative and consequently get a little more
    density for better printing.

    Norm Dresner, Aug 4, 2005
  6. dps

    Nick Fotis Guest

    It depends on the light meter of your camera.
    I have found that most Canon film SLRs tend to underexpose a bit
    (especially when using evaluative metering). This happens usually when
    there are e.g. headlights or street lights in the frame,and the camera
    tries to avoid burning highlights.
    Nikon cameras tend to expose well at 100 to 125 ISO Sensia film (and
    sometimes manage to burn highlights), so your mileage may vary.

    I use center-weighted metering, which is much more stable in my opinion.
    Sensia slide has more tolerance to overexposure (I mistakenly exposed
    some frames 1/2 stop over, and this caused just a bit brighter colours).
    Velvia is more picky about exposure, and usually it's a good idea to err
    to a bit of overexposure in Canon film cameras.

    Regards from HOT Athens,
    Nick Fotis, Aug 4, 2005
  7. dps

    Roger Guest

    Norm, increasing the ISO would cause under exposure. Negative film is
    in general intolerant of underexposure (the shadows get very murky). I
    often decrease the ISO by 1/3 (e.g. 400 to 320)thereby overexposing
    for better results, especially for night street photography.

    I may have missed some context here but increasing the ISO by very
    much would require some push processing to recover the lost detail and
    then by gain contrast and grain.

    Roger, Aug 4, 2005
  8. dps

    Chris Brown Guest

    Sure you don't have that the wrong way round? Increasing the ISO when
    shooting should lead to underexposure, not overexposure, and vice versa.
    Chris Brown, Aug 4, 2005
  9. dps

    MXP Guest

    I always underexpose my slides.
    Run a Velvia 100F on either ISO 125 (F4) or 160 (FE2, F3).
    I project my slides and I am allergic for missing details in the high

    Overexposed slides (even by a 1/2 stop looks very bad).

    Of course if you have snow or a white building and the meter looks directly
    the white thing I compensate for that by overexposing.

    MXP, Aug 4, 2005
  10. To me these differences are too small to matter. I tend to overexpose my
    slides a little bit, because I go for the shadows, and don't mind if the
    highlights are a little washed out. But anything less than 2/3 of an f stop
    is unnoticeable to me.......
    William Graham, Aug 4, 2005
  11. dps

    Tony Polson Guest

    The other way round, surely?

    Exposing ISO film at ISO 80 would be 1/3rd stop OVER exposed. You get
    less highlight detail (more blown out) but the shadows fill in less.
    Tony Polson, Aug 4, 2005
  12. dps

    Alan Browne Guest

    First off, 1/3 over 100 would be ISO 80.

    The reality is that it is all about metering:
    -the camera model and meter and which mode it's in: [ spot, partial,
    scene, matrix, etc.]
    -where you point that meter when you're metering and most importatnly
    _why_ you metered there and with what assumption for highlight or mid
    tone ...

    -and similar variations if an incident meter is used and where in the
    scene the measurement is taken.

    So when one photog with camera xyz spot meters at one place in the scene
    would require rating the film as rated; a different photog with a
    different camera might get the same result if he overexposes by 1/3 of a
    stop. eg: the systems and approach are different ... the exposure is

    Next, what is the purpose of the shot? If it's for projection, then a
    "thick" slide might be preferred over a "thin" slide used for scanning.
    to thin out a slide, overexpose it by 1/3.

    Unless pushing slide film, I expose as rated. If not sure about a shot,
    then over exp it by 1/3. Underexpose? For backlight shote when unsure
    about the metering, yes, good insurance.

    Sensia 100 is a pretty forgiving film (as slide film goes). Shoot as
    rated. In bright sunlight where most of the scene brightly lit, then
    1/3 to 1/2 underexposure will give you a less washed out look ... at the
    expense of pretty dead shaddow areas. Velvia 100F is a very nice film,
    but needs accurate exposure to get punch without blowing the highlights.

    Alan Browne, Aug 5, 2005
  13. the guy I buy film from, suggested me to overexpose Velvia, by changing
    The reason some people expose Velvia 50 at 40 is to reduce the contrast &
    saturation, which given those are the film's strengths as always struck me
    as a bit pointless, why not just use a less contrasty/saturated film

    As for Sensia, assuming you mean Sensia 100, I've always found that it lacks
    contrast & saturation (unless being used for "people" photos, which I rarely
    shoot) and therefore tend to rate it at 125 to increase the
    contrast/saturation by slightly underexposing it and then letting the lab
    process it as normal
    Tony Parkinson, Aug 5, 2005
  14. dps

    Justin Thyme Guest

    If you tell the lab you shot it at ISO80, chances are they would want to
    give the film a 1/3 stop pull in processing and want to charge you extra
    because they are changing the process. This would defeat the purpose,
    because you want them to give standard processing - the ISO80 is to
    compensate for inadequacies in the processing.
    You will have to experiment to find the best combination for you and the lab
    you are using, but instead of shooting the whole roll at 80, try shooting a
    test roll. Set the ISO correct, and for each subject shoot it at a mix of
    exposures - I'd suggest 0, +1/3, & -1/3, maybe even +2/3. My camera will do
    0, +1/3 & -1/3 automatically. Then when you get it processed, see which ones
    turned out the best. +1/3 is equivalent of setting the ISO to 80, +2/3 is
    equivalent to ISO 64, -1/3 is equivalent to 125.
    Justin Thyme, Aug 5, 2005
  15. dps

    Norm Dresner Guest

    Okay, I got the ISO backwards, as I realized as soon as I looked at the
    first posting questioning my sanity. Here's what I should have said:

    I underexpose slides (higher ISO) by 1/3 stop to get a tad more density and
    overexpose negative (lower ISO) (B/W and color) film by the same amount.
    Yes, for slides, it's clearly visible in the final images. For negatives,
    it depends on the printer but overexposing does get a denser negative and
    more shadow detail.

    Additional comments -- and I think I'm really awake now:

    Back in the Stone Age, when I did my own printing, I felt it mattered a
    great deal in my final product. Now that all my 35mm cameras have
    electronics that automatically sense the "DX" data on the cassettes, I'd
    have to set every one of them to an exposure compensation that changed with
    the type of film loaded and then remember what to set it back to for those
    pictures where I intentionally dial in exposure compensation based on the
    scene. I've decided it's more trouble than it's worth but I still do it for
    my 2-1/4"square completely manual camera, the reasoning being that when I
    take pictures with it, I'm doing it to get the best possible image for
    enlarging and every little bit helps.

    Norm Dresner, Aug 5, 2005
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