Metering - Grey Skies

Discussion in 'Beyond the Basics' started by OBrien, May 26, 2005.

  1. OBrien

    OBrien TPF Noob!

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    We get lots of heavy grey skies here in Ireland that I'm having trouble coping with. While the light is flat and uninteresting, my biggest problem is metering where the sky forms part of a picture. A 'correct' exposure removes any detail from the cloud while the subject/foreground is underexposed, metering for the subject or foreground blows the sky out completely, exposing for cloud detail leaves everything else far too underexposed to do anything with. Would a polarizing filter help with this problem? And if so, does it actually reduce the amount light into the lens? It's very frustrating, as waiting for the sun can take a long time round here. Any suggestions would be very welcome.
     
  2. Hertz van Rental

    Hertz van Rental TPF Noob!

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    Are you shooting colour, black&white or digital?
    A polariser won't help much with overcast skies. The light from blue sky has a high component of polarised light so a filter works with it.
    With an overcast the water droplets/ice crystals scatter the light, effectively de-polarising it. In such circumstances the effect of the polarising filter is minimised and it tends to work mainly as a neutral density filter.
    Colour neg film has a relatively low contrast range so either the sky blocks out or the foreground looses detail.
    Your best - and probably only - option is to use a graduated filter. If you get a neutral tinted one it should do what you want. It will work with colour, B&W and digital.
    Colour transparency film might deal with the problem better.
    For B&W you should try using contrast filters (yellow/orange/red/green). They lighten their own colour whilst darkening complementary colours.
    A yellow or orange will solve your problem. Yellow is the one to try first.
     
  3. OBrien

    OBrien TPF Noob!

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    Thanks Hertz - I'm mainly shooting digital these days, so I can do a bit in photoshop to help, but I'm not really keen on doing a lot of manipulation beyond tweaking contrast or saturation.
     
  4. Hertz van Rental

    Hertz van Rental TPF Noob!

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    Try graduated filters then - they should sort out your problem.
     
  5. ksmattfish

    ksmattfish Now 100% DC - not as cool as I once was, but still

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    I'm not sure I understand what you are saying here. Color transparency film is almost always higher contrast than color print film. I would expect greater problems in this sort of situation with slide film than neg film.

    EDIT: Whoops, my bias towards prints shows. Comparing a transparency (as is) to a color print from a neg, the transparency would have a better tonal range for a given lighting condition. I'm just used to seeing blown out highlights in prints from slides.

    I agree that if you don't want to take 2 exposures (one for sky, one for ground) and merge them later in PS, then a neutral grad filter is about your only choice.
     
  6. DIRT

    DIRT TPF Noob!

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    The Zone System, If shooting b&w neg, Meter for the darkest part you want detail in and expose for that and reduce development so that the overexposed sky is in theory "underdeveloped". the highlights are more sensitive to development changes than the shadow areas. you should be able to pull the detail down in the sky.

    I hope you understand this. If you want to know more get the Ansel Adams book "the negative"... VERY helpful

    ***EDIT: sorry, I didnt see that you are shooting digital.***
     
  7. Hertz van Rental

    Hertz van Rental TPF Noob!

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    If the transparency is going to be used for reproduction (a print or in a mag) then it only has a useful contrast range of around two and a half stops - compared to a colour negs useful range of about 4 or 5.
    But viewed by transmitted light a tranny can achieve almost 9 stops.
    Just depends what you want the end result to be. ;)
     
  8. JohnMF

    JohnMF TPF Noob!

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    interesting thread, ive been having this problem with skys myself

    ta
     
  9. selmerdave

    selmerdave TPF Noob!

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    Hertz,

    Can you explain why the difference in contrast between a print from a slide and a slide viewed with light? It would seem that if print film can get 4 or 5 stops the paper is capable of that, and if the slide is "recording" 9 stops of contrast why can't it transmit the 5 that the paper is capable of to a print?

    Dave
     
  10. Hertz van Rental

    Hertz van Rental TPF Noob!

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    Transparencies are designed to be viewed by transmitted light so they can contain a wide contrast range.
    Prints, by their nature, are viewed by reflected light and this reduces the contrast range that they can contain.
    Because of the way colour materials work (chemistry dictating sensitometry) to get a colour print of reasonable contrast range colour negs are actually of quite low contrast.
    To get a print from a transparency you either have to make an interneg and print from that - or use a specialist colour reversal paper.
    Internegs are specialist and very expensive and the end result is approximately what you would have got if you shot neg in the first place - only with more chance of getting faults: scratches, dust, colour casts, contrast variations...
    Also, it is impossible to control the contrast of a colour neg by varying development - this messes with all three layers in the film and you get colour changes. The cost of producing interneg material of different contrasts was prohibitive so they produced just one. This meant that you only got good results if the tranny matched the interneg. Mostly the results were either washed out or very contrasty.
    Printing onto positive paper is even more unsatisfactory as the paper could not be made of low enough contrast to contain more than about four stops. And it was tricky to use - Cibachrome was a real pain for colour filtration and had to be colour-reversal processed. To get it all spot on and get the maximum contrast range possible took considerable time. It took me a whole day once to get three useable prints.
    Very little time, money and effort was put in to solving these problems as nobody used them very much. To give you an example - E6 processing was introduced by Kodak in 1977/78 and we are still using it with only minor modifications. Look at the equivalent improvements in colour neg and B&W.
    It's all been rendered largely accademic now by the use of digital technology and computers.

    It was just found that in practice, to get reasonable results from a transparency that was going to be reproduced in a magazine, two-and-a-half stops gave the best results - keeping detail in the highlights and shadows.
    To understand the reasons fully I'd have to give you the hour long lecture with lots of graphs and diagrams. Your best bet is to get hold of a good book on sensitometry.
     
  11. saddog

    saddog TPF Noob!

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    Gray skies are a fact of life, why does everything always have to have blue sky and white puffy clouds? Overcast days are perfect for getting shadow detail that would be lost on a sunny day. People shot on an overcast don't have raccoon eyes and plants and flowers show a more pastel and natural color.
    I would think more of composition, keeping the sky to a minimum if it bothers you.
     

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