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08-01-2016, 10:20 AM   #1
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28-45mm Vignette w/ filters

Hello, long time lurker, first time poster.
Thanks to info on this site, i picked up a 645z and need some advise. I want to add a 28-45mm with filters to my kit and have a few questions before i pull the trigger.
- Can anyone confirm the maximum thickness of a circular filter on the 28-45mm before vignetting? will regular 8.5mm thick filter vignette?
- I am assuming the Singh Ray Vari-N-Trio (17.3mm) will vignette but by what focal length will that cease to be an issue?
Thank You

08-01-2016, 01:47 PM   #2
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I use Lee filters on mine but I'll dig out something 8.5mm thick and give it a try when I'm back on (Wednesday) if you don't get confirmation from anybody else.

Bob
08-02-2016, 07:06 AM   #3
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Here's a "quick" test for vignetting that can work on any lens, filter, hood, and SLR camera, etc.*

1. Mount the lens/filter/hood that you want to test.
2. Shine a flashlight through the viewfinder into the pentaprism & focusing screen.
3. Hold the camera backwards at about arms length so you can look into the lens and see the brightly lit focusing screen through the aperture of the lens.
4. Next, angle the camera up or down so you are looking into the lens off-axis -- as you angle the camera more, you'll eventually see the edge of the focusing screen appear in the aperture of the lens.
5. Next, angle camera right or left to follow the edge of the focusing screen until you see the corner of the focusing screen.
6. If the edge of the filter or hood clips your view of the edge or corner of the screen, then that filter or hood will definitely vignette.

7. If you stop-down the lens while doing this, you can estimate the f/stop that might lessen the vignette. And if the lit aperture of the stopped-down lens is still clipped by the filter, then you'll know that stopping down will make the vignette worse (i.e., the vignette will be a hard dark shadow on the edge or corner of the stopped-down image).

8. With a bit of skill and a ruler, you can estimate the amount of filter you can add or hood size that can be added although the caveats below do apply!

* Caveats: To the extent that the viewfinder offers less than 100% coverage, the edge or corner of the focusing screen is NOT the edge or corner of the image so that a filter or hood might still vignette if it's close to the image of the edge or corner of lit focusing screen as seen through through lens. (That's especially true for Pentax 35mm & APS-C cameras with SR in which the sensor frame might be shifted during SR, composition-adjustment, horizon adjustment, & astrotracer operations!)

P.S. this test works on the same principle as the Ravenous Bugblatter Beast of Traal in Douglas Adams Hitchhiker's Gide to the Galaxy series -- if you can't see the focusing screen because the filter is in the way, then the sensor can't see you.
08-02-2016, 12:10 PM   #4
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I have just given up on using circular ND-filters, the discolouration is just too bad with these.
I had tested just about all the really expensive ones and now I'm using the Cokin system with their new Nuances series and for the first time, no strange X-shapes, no yellowing, just the same colour, but darker.
but that's just for ND. I am not using polarizers.
and I have decided against the 28-45, too heavy and I ended up using mostly 35mm, so I got the much lighter DA35, which is also sharper at 35 and gives me more room in the bag for the 45-85.

just my 50 cents

cheers
Z

08-02-2016, 08:39 PM   #5
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I sure enjoyed reading this post. Am I gonna try your "quick" test for vignetting? Hell no, but loved reading it, lol.




QuoteOriginally posted by photoptimist Quote
Here's a "quick" test for vignetting that can work on any lens, filter, hood, and SLR camera, etc.*

1. Mount the lens/filter/hood that you want to test.
2. Shine a flashlight through the viewfinder into the pentaprism & focusing screen.
3. Hold the camera backwards at about arms length so you can look into the lens and see the brightly lit focusing screen through the aperture of the lens.
4. Next, angle the camera up or down so you are looking into the lens off-axis -- as you angle the camera more, you'll eventually see the edge of the focusing screen appear in the aperture of the lens.
5. Next, angle camera right or left to follow the edge of the focusing screen until you see the corner of the focusing screen.
6. If the edge of the filter or hood clips your view of the edge or corner of the screen, then that filter or hood will definitely vignette.

7. If you stop-down the lens while doing this, you can estimate the f/stop that might lessen the vignette. And if the lit aperture of the stopped-down lens is still clipped by the filter, then you'll know that stopping down will make the vignette worse (i.e., the vignette will be a hard dark shadow on the edge or corner of the stopped-down image).

8. With a bit of skill and a ruler, you can estimate the amount of filter you can add or hood size that can be added although the caveats below do apply!

* Caveats: To the extent that the viewfinder offers less than 100% coverage, the edge or corner of the focusing screen is NOT the edge or corner of the image so that a filter or hood might still vignette if it's close to the image of the edge or corner of lit focusing screen as seen through through lens. (That's especially true for Pentax 35mm & APS-C cameras with SR in which the sensor frame might be shifted during SR, composition-adjustment, horizon adjustment, & astrotracer operations!)

P.S. this test works on the same principle as the Ravenous Bugblatter Beast of Traal in Douglas Adams Hitchhiker's Gide to the Galaxy series -- if you can't see the focusing screen because the filter is in the way, then the sensor can't see you.
08-03-2016, 10:05 AM   #6
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QuoteOriginally posted by mikeSF Quote
I sure enjoyed reading this post. Am I gonna try your "quick" test for vignetting? Hell no, but loved reading it, lol.
Thanks and ! One can also use this method to see if a teleconverter is clipping the lens aperture and to guesstimate the shape of the bokeh of a lens.
08-03-2016, 12:25 PM   #7
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QuoteOriginally posted by photoptimist Quote
Thanks and ! One can also use this method to see if a teleconverter is clipping the lens aperture and to guesstimate the shape of the bokeh of a lens.
ah, i was wondering same
08-04-2016, 09:39 AM   #8
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My filters (B&W CPL and UV) are only 4mm each so I was able to test at around 10mm by installing them with the screw barely engaged.....no obvious vignetting.

I also tried the method outlined in post #3 and, based on that test, there seems to be a lot more latitude for thickness before vignetting would be seen. An estimate of where my eyeline passed the filter rim would be 20mm or more.

Bob

08-05-2016, 12:38 PM - 1 Like   #9
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Original Poster
Thank you everyone for your help and suggestions.
Bob, cheers for taking the time to test. I really appreciate it. I had sent an email to B&H as well and they reiterated your findings. 8mm filter will not cause any vignetting.
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