So really, the polariser would have no effect at all?No overkill at all, as any polarizer effect would vanish behind that of the infrared exposure.
I doubt that the IR and near IR light is plane polarized in the first place, and I doubt even more that the polarizer interacts in any meaningful way with IR light.So really, the polariser would have no effect at all?
Attach polariser, adjust accordingly, attach r72Assuming one could see through the R72 filter so that one could adjust the polarizer ... Shoot the IR film and forget the polarizer.
Yes, that was indeed why I wondered if using the polariser too would enhance the effect of the r72 filter, as in would it make white clouds stand out even more and make blue skies even inkier black. Seems like the consensus, though, is to use the r72 on its own.Well, a polarizer can have two effects:
-) darkening polarized part of the blue sky (I thought that was the intended effect the OP wanted)
That effect would be smaller than the effect of darkening the sky by blocking all blue light
-) darkening reflections of infrared-light
However with infrared light the blocking effect of the polarizer may be less than with visible light.
Yes, I think I'll go down this route - a shot with a polariser and one without for comparison. I'm guessing a polariser at its most effective rotation is around 2 stops of light, so adding that to the general opinion that an r72 is 4 or 5 stops (though given how dark an r72 actually is, 4 or 5 stops seems quite a low figure), I'll obviously over expose the totally non filtered reading by 6 stops when using both filters together.I don't know that it would create a visible difference, but if you can afford to waste a few frames both with and without the polarizer, I think we'd enjoy comparing. It can't hurt to test. Of course you'd need the exact same subject and framing, same EV (accounting for the polarizer), and on a tripod of course.
FIIIIIGHT!There’s only one way to find out.
Attach polariser, adjust accordingly, attach r72
Except it WILL work because I have a screw in polariser (2, actually) which itself has a thread at the front to attach other screw in filters to it. So...Except that will not work because the polarizer is adjusted by turning the outer most filter and then one cannot attach to that outer filter but if one could attaching the R72 filter would change the polarizer setting. Most if not all polarizing filters cannot have another filter added after them.
Except it WILL work because I have a screw in polariser (2, actually) which itself has a thread at the front to attach other screw in filters to it. So...
1) attach polariser to lens and rotate filter to achieve desired effect.
2) while maintaining a grip with one hand on the polariser so as to not allow it to rotate, attach screw in r72 to front of polariser.
3) there you go!
No luck needed, just care to make sure the polariser doesn't move when attaching the r72Good luck with that.
I think you know what you need to know, but the use of "over-exposure" causes me discomfort.With regards to the 4 stops of overexposure: this is something I'm putting my trust in, having read loads of reviews about shooting with this film and filter combo, because the exposure graph in the viewfinder was indicating massive underexposure. I just had to tell myself that that's because 'ordinary' light is blocked by the filter so the graph would obviously indicate underexposure when the filter's attached. Hopefully the 4 stops overexposure is the right ballpark figure to have capturec the infrared light.
But isn't that what I did anyway by adjusting the non filtered speed by 4 stops overexposure when putting the filter on? With the 2 shots I did today I got a metered unfiltered shutter speed of 1/250th with the aperture set to f11 and f13, then I manually set the speed to 1/15th, ie., 4 stops overexposure, with the filter attached.I think you know what you need to know, but the use of "over-exposure" causes me discomfort.
The film and meter are sensitive to visible light. The film is also sensitive to near IR light, even if the meter isn't. The near IR light is much less intense (~4 stops) then the visible light. Even though we cannot effectively meter near IR light, experience allows us to reach conclusions about how much near IR light is around when a certain amount of visible light is there.
If you don't use a filter to block the visible light, it will overwhelm the near IR light. As a result, what you see on the film is entirely due to the visible light.
The R72 filter blocks the visible light but lets the much less intense (~4 stops) light above 720nm (near IR and IR light) through to the film.
So you meter the visible light, assume that the near IR light is 4 stops less intense, block the visible light with the R72 filter, set the camera for that much less intense near IR light and shoot away.
I'll be interested to see the effect of 4 stops overexposure. Please show us your "positive" negs. From what I have gleaned from various threads on the R72 the best IR effect seems to come from between 5-6 stops over. If you have used all of the film by now then my next suggestion is too late but you might want to try the same shot in 3 consecutive exposures of 4,5 and 6 stops over to see what, if any, differences there are and which is the best for you. My experience with SFX was that a black sky was achievable with a red 25 and based on this I don't think a blacker sky would be possible but what is crucial is how much "Wood effect" you get with a R72 and 4,5 and 6 stops over. That "Wood effect" which turns deciduous foliage a silvery-white was almost non existent with a red 25But isn't that what I did anyway by adjusting the non filtered speed by 4 stops overexposure when putting the filter on? With the 2 shots I did today I got a metered unfiltered shutter speed of 1/250th with the aperture set to f11 and f13, then I manually set the speed to 1/15th, ie., 4 stops overexposure, with the filter attached.
It is the reference to "overexposure" that concerns me. To me, that means too much exposure for the film used, not an increase of exposure to intentionally compensate for a filter.But isn't that what I did anyway by adjusting the non filtered speed by 4 stops overexposure when putting the filter on? With the 2 shots I did today I got a metered unfiltered shutter speed of 1/250th with the aperture set to f11 and f13, then I manually set the speed to 1/15th, ie., 4 stops overexposure, with the filter attached.
Sirius,I do not get the four stops over thing either. The film manufacturers know much more than you do about the film. Just shot it at box speed and it will work as advertised.
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?