Using a Red Filter

Discussion in 'Black and White' started by stripmonkey, Aug 6, 2019.

  1. Evening everyone.

    Has anyone successfully used a red filter to photograph a moody sky? I’ve tried a few times and never really seen any difference with or without. I scan my negatives at the moment until I can build a darkroom, but even through the loupe there isn’t much difference. I normally add 2 - 3 stops of exposure when using the filter as suggested too.

    Many thanks, Rob
     
  2. I don't have any scans readily at hand, but yes a red filter generally makes a clear sky turn nice and dark. Of course, an overcast sky won't do this and will still be rendered light.

    When you say you add 2-3 stops of exposure, are you using a TTL meter or a separate/non-TTL? If you're using a TTL meter and still adding in a filter factor, you're going to end up with very thick negatives that can be difficult to scan(or print).
     
    bgelfand likes this.
  3. If your developed negatives are on the thin side, you will be hard pressed to see the difference in the negatives. Normal exposure / Normal development will make the graduations very ez to spot on a light table. Using the deep red (25A) filter sometimes makes the sky / cloud separation a bit on the wild side. The most classic good effect with this filter is Ansel Adams picture of Half Dome. I personally like to use a G (orange) filter with most out doors b/w scenes. Pops the sky without sending ink all over the remaining scene. Here is my use of the G filter. Bessa I, UFX100 & 510-Pyro developer. V600 scan. My filter factor for the G is +1.5f 2k18-2k15-027-003-ce bc.jpg
     
    robertgiles and James Bryant like this.
  4. It depends upon what you mean by "moody sky". If you mean overcast with no blue sky showing, ben_hutcherson (above) has answered your question.

    A red filter passes red light and blocks blue/cyan - the complimentary color. In black and white this results in a darker sky and increased contrast in which white clouds stand out. For an overcast sky there is no distinct blue feature to suppress and no white cloud to stand out, so no increased contrast.
     
  5. Thanks for all of your replies :)

    I shoot with a Hasselblad 500 c/m and use a Weston Master V light meter to measure the exposure, and when using the red filter I add 2-3 stops to the reading given. Would you say this is the correct method?

    I’m wondering whether the sky in the shot was “blue enough” now, perhaps I was shooting a little towards the sun. I’ll give it another go when it’s deep blue and see what happens.
     
  6. It depends upon the filter; there are many "red" filters each with a different filter factor. B+W lists two red filters for black and white - 090 filter a Wratten 25 equivalent with a filter factor of approximately 5 (2 1/3 stops) and a darker 091 a Wratten 29 equivalent with a filter factor 8 (3 stops). You are in the right ballpark.

    To be more precise, take the filter off your camera. Set a fixed aperture on your light meter. Measure the sky, away from the sun, with your meter; note the reading. Now hold the filter in front of the meter and measure the same sky through the filter; note the reading. Take a ratio of the shutter speeds. this is your filter factor. The filter factor is expressed in terms of shutter speed ratios at a fixed aperture, NOT aperture stops. You must convert to get stops. Stops would be Log-base-2 of the filter factor. Since most calculators do not have a Log-base-2 key, the easiest way to compute this is Log (filter factor) / Log 2 - the Log of the filter factor divided by the Log of the digit 2. Or you could set a fixed speed on the light meter, take the two readings, and compute a ratio of the two f-stops.
     
  7. If the clouds have cut out the "blue" light, then a red filter will not darken much.

    Otherwise, the effect can be very striking, almost infrared-like.
    Greece-Akropolis-Parthenon-view.jpg
     
  8. A grey sky will remain grey no matter what colour of filter you use. As has already been said, a red, yellow or orange filter will only darken a blue sky.

    To me, a moody sky would indicate grey and overcast conditions.

    BTW, most Weston Master V meters have a dead or dying selenium cell these days, unless the cell has been replaced. A quick check is to point the meter at an area that gives a reading of 10 on the high scale. Keeping the meter pointed at the same area or light source, open the baffle to put the meter into the low range. If the needle doesn't reach 10 on the low scale, or very close, then you have a faulty cell.

    There's no cure I'm afraid. 'Megatron' the company that once undertook Weston repairs and cell replacement, is long out of business. So if the cell has a low output, it's time for a new meter. Preferably one that uses a silicon diode as sensor.
     
    Last edited: Aug 6, 2019
  9. Yes . . . A red filter will darken the blue in the sky and make the clouds stand out more. If there is no blue, it will have little effect. A polarizing filter can often be used to the same effect and MAY have an effect on a completely cloudy sky. The answer, generally, when working with a mostly grey, overcast, sky, is to burn the sky at a higher contrast while printing.
     
  10. I agree with what Ed said, as well as others. if there is only grey sky, filters will do nothing.

    try doing some tests. This is what I did when I first started shooting with filters many many years ago. Find a nice landscape scene with clouds as well as blue sky. then shoot 1 frame with no filter and then repeat the shot with all the filters you own or will use. I did it with a yellow, dark yellow (G), orange, dark orange, red, light green, dark green and IR. then print or scan the results. a contact sheet really helps here as its way easier to view all the results next to each other. I used a 6x9 camera which made the results large enough to view without a loupe. anyway, it was really helpful.
     
  11. I do like a red filter (25 or 29), but if I have to take just one filter with me, it's an orange.
     
  12. From back in the day when most photographers shot monochrome:

    B&W-Filters.jpg
     
    denny_rane likes this.
  13. I used to shoot almost all of my B&W with a yellow filter. Not the deep yellow. Later, I pretty much stopped using them at all.
     
    denny_rane likes this.
  14. Something else that just occurred to me:

    A "proper" R25 filter will only transmit the wavelengths of light from ~580nm on. An R29 is a bit different, and I think cuts off in the low 600nm range.

    Most decent name brand filters-meaning everything from the likes of B+W on down to the cheap Promasters my local shop sells-are good about actually cutting off at their designated wavelength. Another local shop has thousands of used filters in an old library card catalog, and I've bought bunches out of that cabinet. If it's an unknown brand, I often check its transmission(a simple thing for me to do, but I realize not everyone has access to the equipment to do it) and have rarely found an older filter that didn't match what it claimed.

    By contrast, though, I'll mention that a few years back I was hunting for a 67mm red filter, and since I'm a bit averse to the new prices for most major brands, I thought I'd try a no-name Chinese one. As soon as I got it, I thought the color looked "off" for an R25, and a quick check in the spectrophotometer showed why-even though it did cut-off at 580nm, it started transmitting again around 450nm and kept going down to the typical ~370nm cut-off for optical glass. This made the filter basically useless for its intended purpose.

    If you look through the hundreds of filters I have, you'll find plenty of B+Ws, Nikons, Hoyas, and other good brands. I'm also not shy about Tiffens and even "generic" brands of whatever age(there's plenty of Vivitars, Spiratones, and others kicking around). As long as they do what they're supposed to do, I'll use them if I have a need for the filter's specific affect without much thought. The problem is that there are filters out there that DON'T do what they claimed. If you have access to a UV-VIS spectrophotometer(and know how to use it) checking a filter can take 5 minutes or less. I've gone through a stack of them in 10 minutes, since I spend most of the time turning it on and setting it up, and for the resolution needed for these purposes it takes about 30 seconds to actually measure one. If you don't have that, though, stick to known brands.
     
  15. My experience with TTL meters in my Nikon SLR bodies is that +1 stop exposure compensation for a Nikon R60 red filter (IIRC close to a 25A) works out pretty well. If I'm shooting my old clunker Mamiya TLR and metering with my Pentax 1 degree spotmeter, I have step-up rings that allow me to put a 52mm filter on both and use the same +1 stop rule. Otherwise, it's about a +3 exposure adujstment for the spotmeter reading with no filter.
     
  16. SCL

    SCL

    My experience has been varied, but in general I've narrowed it down to +1 for med yellow, +2 for med green, +3 for red. Still trying to get it right for orange (G) though.
     
  17. for my hoya G filters, I use +1 1/2 stop compensation. that's direct from hoya's web site
     
  18. In the long run, there is no such thing as a "correct" filter factor for any of these filters. The effect varies based on the color content of the subject and the lighting along with the effect that you trying to get from the filter and exposure to begin with.
     
  19. This is very true, but for most situations, the exposure latitude should be enough,
    except in the most unusual cases. Some light meters have spectral sensitivities
    that might not accurately meter through filters. Next, there is film spectral sensitivity.

    Kodak gives filter factors on the data sheet for most films, including separately
    for daylight and tungsten. For some cases, that might be better than filter
    company data sheets.

    https://imaging.kodakalaris.com/sites/prod/files/files/products/f4001_tmax_3200.pdf
     

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