Working hypothesis- Black Pro Mist Filter may reduce Fringing in High Contrast Images
So, this is a working hypothesis. I need to make some scientific-ish tests and put this hypothesis to the test. I shot two different scenes with the Pentax M 50mm f1.4, both scenes high contrast with bright sunlight. The difference is on one I had no filter attached, on the other I was using a Tiffen 1/2 Black Pro Mist 82mm, attached with a 49-82mm step up ring. Reviewing the images shows some color fringing in the images from the non-filter scene and so far no fringing from the scene where the filter was used.
I wouldn’t think the filter would have much impact to color fringing, so I’m going to try to put together some scientific-ish experiments to see if there’s any benefit to using a black pro mist filter to decrease color fringing. I also ordered a Tiffen 82mm Circular Polarizer to throw into the test. If I notice any benefit from the 1/2 filter perhaps I’ll use different strengths to see if there’s any performance difference.
I anticipate I’ll find the filter has no impact on fringing and the two scenes were just different enough to not produce fringing in the one scene. Anyone interested in this?
hey sounds interesting I never thought about that being a benefit of a BPM filter. It makes sense thinking about it though that the blooming highlights would cover the color fringing. Tests sound interesting
Very interesting. Is is possible for you to post a link or upload the files somewhere? Based on my very limited knowledge of light and lenses I think it could be plausible that a Black Pro Mist filter could fix chromatic aberration. CA is, as I understand it, caused by the different wavelengths of light not converging at the same time on the sensor. I could see how the semi-random diffraction caused by a BPM filter could cause an averaging effect on the light, slowing down, or more accurately, increasing the distance traveled by some of the light causing the light to re-converge at a more consistent rate. I'm very interested to know more. Which camera/lens was used did you notice this on? I may also try to repeat this if you have any success.
Pentax M 50mm F1.4 on a Canon R6 Mark II.
BPM filters alter contrast so it’s not implausible they might impact fringing on high contrast edges.
I have two Nanlite FS150 LED video lights that are pretty bright. I could probably set up some tests in my basement. If the 1/2 BPM filter does decrease fringing my thought is to drop to a 1/8 strength and see if it has the same effect.
Ok, first test results are in. I think the results are a bit subjective. For this test I mounted the camera (Canon R6 Mk2) on a tripod with the SMC Pentax-M 50mm f/1.4 lens affixed via Fotasy adapter. I set up a Nanlite FS150 with 36 inch Godox soft box behind the test subject and turned brightness to 100%. I set up a second FS150 in front with a Good strip box at 85%. I took three images. Settings were 1/125, f2.8, ISO 100. Images were loaded into Lightroom classic, profile set to Camera Faithful, WB to 5500K. I think the no-filter images show a touch more color fringing than the with-filter images, though, the with-filter images look a bit washed out due to the halation of the BPM filter. Note the BPM filter cut exposure by 1/4 stop so ISO was 125 for those shots, all other settings the same. So far subjective test results. I'm going to change test subjects and angle of the rear light and try again. The fringing is visible at the top of the light stand holding the stuffed animal.
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Quote from Cory Maben on June 24, 2024, 5:35 amVery interesting. Is is possible for you to post a link or upload the files somewhere? Based on my very limited knowledge of light and lenses I think it could be plausible that a Black Pro Mist filter could fix chromatic aberration. CA is, as I understand it, caused by the different wavelengths of light not converging at the same time on the sensor. I could see how the semi-random diffraction caused by a BPM filter could cause an averaging effect on the light, slowing down, or more accurately, increasing the distance traveled by some of the light causing the light to re-converge at a more consistent rate. I'm very interested to know more. Which camera/lens was used did you notice this on? I may also try to repeat this if you have any success.
Its physically impossible to correct CA in front of the lens where no CA has happened yet. All the different wavelength that enter the filter from the same light source are exactly parallel to each other and the only effect possible for any optical element is to make them diverge.
You'd need at least 2 elements to make diverging light rays cross but for the actual lens to work properly you want parallel light (collimated) which is practically impossible to create.
Apochromatic lenses or lenses in general don't change the time or distance to the sensor for the different wavelengths (well they do but is irrelevant, light is way too fast).
APO works by focusing the different wavelength at the same point (not time).
I think @kcphotogeek is correct, most likely the effect of the filter hides the CA.
Another less likely possibility would be that the CA is caused by a certain wavelength (near UV or IR range) which the cameras internal filter does not block but the Mist filter does.
Quote from Anthony Grizanti on June 24, 2024, 6:13 pmOk, first test results are in. I think the results are a bit subjective. For this test I mounted the camera (Canon R6 Mk2) on a tripod with the SMC Pentax-M 50mm f/1.4 lens affixed via Fotasy adapter. I set up a Nanlite FS150 with 36 inch Godox soft box behind the test subject and turned brightness to 100%. I set up a second FS150 in front with a Good strip box at 85%. I took three images. Settings were 1/125, f2.8, ISO 100. Images were loaded into Lightroom classic, profile set to Camera Faithful, WB to 5500K. I think the no-filter images show a touch more color fringing than the with-filter images, though, the with-filter images look a bit washed out due to the halation of the BPM filter. Note the BPM filter cut exposure by 1/4 stop so ISO was 125 for those shots, all other settings the same. So far subjective test results. I'm going to change test subjects and angle of the rear light and try again. The fringing is visible at the top of the light stand holding the stuffed animal.
You could try without the light from the front, a stuffed animal silhouette shot basically.
Quote from Kamera Brand on June 24, 2024, 6:42 pmQuote from Cory Maben on June 24, 2024, 5:35 amVery interesting. Is is possible for you to post a link or upload the files somewhere? Based on my very limited knowledge of light and lenses I think it could be plausible that a Black Pro Mist filter could fix chromatic aberration. CA is, as I understand it, caused by the different wavelengths of light not converging at the same time on the sensor. I could see how the semi-random diffraction caused by a BPM filter could cause an averaging effect on the light, slowing down, or more accurately, increasing the distance traveled by some of the light causing the light to re-converge at a more consistent rate. I'm very interested to know more. Which camera/lens was used did you notice this on? I may also try to repeat this if you have any success.
Its physically impossible to correct CA in front of the lens where no CA has happened yet. All the different wavelength that enter the filter from the same light source are exactly parallel to each other and the only effect possible for any optical element is to make them diverge.
You'd need at least 2 elements to make diverging light rays cross but for the actual lens to work properly you want parallel light (collimated) which is practically impossible to create.Apochromatic lenses or lenses in general don't change the time or distance to the sensor for the different wavelengths (well they do but is irrelevant, light is way too fast).
APO works by focusing the different wavelength at the same point (not time).I think @kcphotogeek is correct, most likely the effect of the filter hides the CA.
Another less likely possibility would be that the CA is caused by a certain wavelength (near UV or IR range) which the cameras internal filter does not block but the Mist filter does.
okay yeah, that does make sense. I was just thinking because the filter itself isn't uniformly hazy, that some of the light passes through unaffected while other light is more affected by the diffraction. But looking at the photos I also agree that the CA isn't reduced in the filtered image, but merely masked by the halation
Quote from Anthony Grizanti on June 24, 2024, 6:13 pmOk, first test results are in. I think the results are a bit subjective. For this test I mounted the camera (Canon R6 Mk2) on a tripod with the SMC Pentax-M 50mm f/1.4 lens affixed via Fotasy adapter. I set up a Nanlite FS150 with 36 inch Godox soft box behind the test subject and turned brightness to 100%. I set up a second FS150 in front with a Good strip box at 85%. I took three images. Settings were 1/125, f2.8, ISO 100. Images were loaded into Lightroom classic, profile set to Camera Faithful, WB to 5500K. I think the no-filter images show a touch more color fringing than the with-filter images, though, the with-filter images look a bit washed out due to the halation of the BPM filter. Note the BPM filter cut exposure by 1/4 stop so ISO was 125 for those shots, all other settings the same. So far subjective test results. I'm going to change test subjects and angle of the rear light and try again. The fringing is visible at the top of the light stand holding the stuffed animal.
Thanks for posting these! It's hard to tell exactly what's happening because I can only find that one instance of CA where you mentioned at the very top. Maybe try something with a darker and harder edge to generate more CA. But I currently also think that the filter isn't reducing the CA, as it's still visible, it's just much lower contrast making it harder to see
Yes, you’re correct, more or less hiding the CA since CA happens inside the lens. We’d need at least an corrective element somewhere to correct for it. I do think the BPM is hiding the CA, to some extend. I’ll try the silhouette shot.
