Okay, so I couldn't resist going straight into a test right after my last post.
This is by no means a conclusive or very scientific test, there are a lot of variables I have not accounted for, but perhaps it's close enough to a real world experience to be useful. I feel that these test images don't show the full extent of the green shift because it becomes a lot more apparent in skin tones than on test charts. Nonetheless, my corrections to bring balance are consistent with my experience of the lens over the last 2 or so years.
METHODOLGY - - An X-RITE video color chart was lit by a single Aputure B7C bare bulb set to 5600k.
- The charts aren't super sharp because I did this handheld and quickly. Sorry!
- Chart was measured with an illuminati light meter and read 5080k.
- Camera was a BM pocket 6k Pro, no ND, 400iso, WB 5100k, tint 10.
- All lenses were set to f/2.8, and framed by eye.
- The chart was lit by false color so that the middle gray section was as close to uniformly green as I could get it.
- 32mm lens at 2.8 let in more light than any of the other lenses, so the intensity of the light source was reduced slightly to get consistent exposure.
- Lenses all had the exact same Hoya UV filtration filter. No other filtration was present.
- All clips were converted from BM Gen 5 LOG to Rec.709 gamma 2.4 using a color space transform in DR 18.
IMAGES25mm Straight out of Camera32mm Straight out of Camera50mm Straight out of Camera85mm Straight out of Camera25mm Corrected via RGB picker in Resolve on middle gray chart patchTo correct the green cast, a measurement was taken using the RGB picker in the Resolve viewer pane, and chosen at a point that seemed to generally represent the middle gray patch accurately.
To bring the 25mm into proper WB and within the tolerances of the other lenses,
the following corrections were necessary:
PRINTER LIGHTS:+ 0.5pts RED
- 3pts GREEN
+ 1pts BLUE
OR CAN BE ACHIEVED IN RAW USING:
RAW WB:+20 magenta tint (total corrected tint = +30)
-200 kelvin (total corrected WB = 4900k)
PERSONAL CONCLUSIONSThese are great lenses, and they are a joy to shoot with. In fact, they are just about the only lens set I use on most of my work. But I wish someone had really explained it to me that the 25mm is far off enough from the other three that it must be accounted for
specifically, either in-camera, or in post.
The other three can be swapped no problem and WB can be left more or less untouched, but not so with the 25mm. I still love them, but find it to be a bit of a bummer, and also a possible reason that SLRMagic has essentially put that focal length on perpetual sale...
It's just a shame to find myself hesitating to use a focal length because I'm concerned about having to do extra work to get it to agree with the rest of the matched set.
This is, of course, a very unofficial/unscientific/average joe .02 cents kind of test..
And SLRMagic, if somehow you are reading this, and I'm just an unlucky fellow with weird green copy, don't hesitate to get in touch to help me fix it!
All the best!