Filter colour / strength

Discussion in 'Accessories' started by AgBr, May 4, 2017.

  1. I just bought a yellow filter for my Hasselblad V system, in the B60 mount. The filter rim says:
    1,5x Y – 0,5 (4)

    How should these codes be interpreted? I looked up the list of Wratten numbers, but they certainly don't correspond to the info on my filter.

    Did Hasselblad produce different versions (e.g. light yellow / deep yellow etc.) or is there just one filter for each colour?

    Many thanks in advance.

    Peter
     
  2. I'm not sure how Hassie grades the filters, but the standard "Wratten" description is a multi-strength set. (2a~13)
    I'm guessing the 1,5 (Y) is the K2.
    Wratten number - Wikipedia
     
    AgBr likes this.
  3. I would take the "1,5 x" to mean a filter factor of 1.5, meaning that the required exposure is 1.5 times the unfiltered exposure.

    As a guess, the "-0,5" may be suggesting an "exposure compensation" value of 1/2 EV, meaning Exposure Value, where each EV is equivalent to a full f-stop exposure change. (This is an alternate way of adjusting.)

    I have no idea what the "(4)" might be; perhaps it's just a number sequence that Hasselblad uses.

    I think there's a good chance that chazfenn is right about the "k2" filter, but I prefer the more modern Wratten #8 designation. Given that the Wratten series has stronger yellow filters, I would imagine that Hasselblad also does.

    I'm really just guessing, though, so if a knowledgeable Hasselblad user weighs in you should go with what they say.
     
  4. I think the #8 is a yellow-green, I'm guessing the K2 because of the filter factor (1.5) on his filter matches that. The deep yellow is a 2X.
    Filters by the Wratten Numbers
     
  5. Hi chazfenn, I see from another post that you've been around the business for a while, so now I understand why you use the K2 designation. But my "modern" (1990) Kodak Filter Handbook has a cross-reference list: Wratten #8 = "discontinued designation" K2.

    Ps, I'm a believer in the filter factor, at least with hard-cutting filters like this, going with the film (and sometimes light source), not strictly with the filter itself, so I'm a little iffy on Hassie's designated factor. (By way of reference, Kodak T-max 100/400 give daylight factor of 1.5 for Wratten #8, but Tri-X 400 has a factor of 2. Both have lower factors with tungsten light, only 1.2 for the T-max.)

    Welcome to photo.net, by the way.
     
  6. I don't see any point in getting overly picky about filter factors for B&W film. The difference between a factor of 1.5 and 1.2 is only 1/3rd of a stop, and I don't think 'blad lenses can be set to one-third stop intervals. Even if the shutter speed and aperture calibrations are reliable to that degree of accuracy.

    On cameras using TTL metering the FF is pretty irrelevant anyway, since the meter will automatically compensate for lighting CT and filter density - that's assuming the meter has an identical response to the film. A big assumption, both for TTL and handheld meters!
     
    Last edited: May 5, 2017
  7. I should have been more clear; my intended point was that a factor written on the side of a filter does not necessarily ID that filter. Mainly because, in the case of a hard-cutting filter, there is a lot of ambiguity in what that factor should be. My example shows that a correct factor for the #8 filter could range between 1.2 and 2, just for those two films/lighting.

    When you carry the filter situation a little farther, to hard cutting red filters (like Wratten #25 and #29), metering through the filter is not very reliable. A lot of people would suggest doing test shots for any critical work. But... if one simply follows the instructions on the film data sheet (and the lighting conditions match) then no tests would likely be necessary.

    I tend to be perhaps overly finicky on certain matters. Mostly they are things that have caused me difficulties in my photography career because I had improperly "learned" them. So the current "me" likes to explain things in the way that the young "me" would've wanted to know.
     
    AgBr likes this.
  8. Thanks a lot for the helpful replies. The filter looks rather light/pale and definitely not as deep yellow as the Y52 Tamron filter I use on my Rollei 35S (30.5mm, made for their 500mm mirror lens). It doesn't look at all greenish either, but I am not an experienced observer of filters. I suppose it is safe to assume, or very likely at least, that half a stop of exposure compensation should be used.

    Best,
    Peter
     
  9. I'd test with a narrow bracket the first time out.
    With B&W film a med yellow isn't too drastic but the effect will be changed slightly by exposure (under adds effect & over lessens it). if you can go -1/4, -1/2, -3/4 & pick th one you like as your "personal" setting.
     
    AgBr likes this.
  10. I'm pretty sure Hasselblad lenses can't be set to an accuracy of 1/4 stop, and even if they could, a 1/4 stop difference in exposure makes an almost invisible difference to a B&W negative. Processing variations could easily wipe out such a small exposure change from film to film.

    Besides, giving filter factors in linear exposure time multipliers is pretty useless and misleading. A time factor of 1.5 is an exposure increase of 0.59 stops to be pedantically precise, and no mechanical camera shutter or aperture mechanism allows a setting so exact.

    For all practical purposes, increasing the exposure by half-a-stop using the aperture will be about as good as it gets.
     
  11. Hasselblad lenses can be easily set to the nearest half stop. That means they can never be more than 1/4 stop from the "correct" (measured) setting. Some meters read to the nearest 1/10 stop, including my Sekonic 508. Whether it is accurate to that level is questionable.

    1/4 stop makes a noticeable difference when adjusting exposure in Lightroom. When making adjustments, I usually round to the nearest 1/2 stop, or the nearest 3 dB when mixing audio (the acoustic equivalent of one stop). When I was doing process control, I would read temperature to 0.01 degrees, accurate to about 0.2 deg, but displayed to the nearest degree. When the QA folks saw 0.1 degrees, they began to think it was important. (you can hardly get less than a 1 degree gradient in a cup of hot coffee, with stirring).

    That's why i am a digital skeptic. Believe, yes, but 'trust and verify."
     
  12. Lightroom isn't a B&W negative.

    I'd defy anyone to decisively tell apart prints made from negatives with only 1/4 stop exposure difference between them, provided the printing density was matched of course.

    Consistent exposures within 1/4 stop across different subjects, film batches, processing batches and aperture/shutter mechanical camera settings are about as likely as snow in a heatwave in Tahiti.

    Being only able to set 1/2 stop intervals means you can't possibly bracket in 1/4 stops. And it certainly doesn't guarantee being only 1/4 stop away from the "correct" exposure - whatever that is!
     
    Last edited: May 7, 2017
    AgBr likes this.
  13. Vincent Peri

    Vincent Peri Metairie, LA

    AgBr likes this.
  14. Thanks, again, for all the explanations and suggestions. For B/W, I use Ilford Delta 400 90% of the time. If I understand the online data sheet correctly, the filter factor indicated by the manufacturer can be followed for this film. Also, TTL metering will yield correct results in most cases (again, according to Ilford), which I can get from the Hasselblad 205FCC. Shutter speeds can be adjusted in half-stop intervals (like the aperture), but in the automatic modes, increments of 1/12 EV-step are used from 1/2000s to 16s. The latter seems to be exposure modifications on an insanely detailed level, which I don't even know if the shutter's accuracy (or lens apertures' precision for that matter) can meet.

    Peter
     
  15. To clarify I'm not suggesting the exposure in & of itself will be much different, its more subtle than that as I explained originally. What may be noticeable is the filters effect on different colored objects. Filter effect decreases & increases with small exposure changes.
     

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