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07-03-2016, 04:48 PM   #1
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Upgrading from K-30 to K-1

Hello All,

I recently upgraded from the K-30 to the K-1 including the purchase of the HD Pentax-D FA 28-105 mm lens.

Since the lens is a larger diameter than my other lenses I also purchased a [circular] polarizer and ND filter kit.

What I've noticed recently is that with the polarizer and an ND filter on the lens it creates a vignette in the top-left and top-right corners of the image. But it doesn't seem to create one in the bottom-left and bottom-right corners unless it just happens to be the composition of the photo.

This didn't happen with my K-30. On my K-30 I used the polarizer and ND filter together all the time (especially with my waterfall photographs).

Am I doing something wrong with the new lens that is causing this vignetting? Could it be that my ND filter is not screwed on correctly?

Any thoughts and ideas on how to avoid this would be greatly appreciated. I leave for Montana in a week so I'm hoping to figure this out before I leave.

Thanks!

MrMontana1889
(Kris)

07-03-2016, 04:58 PM   #2
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QuoteOriginally posted by MrMontana1889 Quote
Hello All,

I recently upgraded from the K-30 to the K-1 including the purchase of the HD Pentax-D FA 28-105 mm lens.

Since the lens is a larger diameter than my other lenses I also purchased a [circular] polarizer and ND filter kit.

What I've noticed recently is that with the polarizer and an ND filter on the lens it creates a vignette in the top-left and top-right corners of the image. But it doesn't seem to create one in the bottom-left and bottom-right corners unless it just happens to be the composition of the photo.

This didn't happen with my K-30. On my K-30 I used the polarizer and ND filter together all the time (especially with my waterfall photographs).

Am I doing something wrong with the new lens that is causing this vignetting? Could it be that my ND filter is not screwed on correctly?

Any thoughts and ideas on how to avoid this would be greatly appreciated. I leave for Montana in a week so I'm hoping to figure this out before I leave.

Thanks!

MrMontana1889
(Kris)
The polarizer only darkens part of the frame, so the location of the vignetting will depend on how you turn it.

Adam
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07-03-2016, 05:31 PM   #3
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At wide angles CPLs may cause darkening in over polarized areas vs less polarized...
07-03-2016, 06:31 PM   #4
dms
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It also maybe the combined (2) filters are too much (a PL is quite a bit thicker than other filters)--and the vignette shows on top because something in the lens/hood is not perfectly plumb. Try w/o the ND filter.

Take a picture of a blank wall--but with lens stopped down and focus at infinity. If the light is not polarized by the wall it will tell you more.

BTW some lenses (usually wide angle ones) don't accept PL w/o vignetting. or do so unless the PL is a slim design.


Last edited by dms; 07-03-2016 at 06:46 PM.
07-03-2016, 07:04 PM   #5
Tas
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Vignette at what focal lengths

This might not be relevant to you, but you didn't mention focal lengths therefore I'll provide feedback on my experience of CPL and ND filters at the wide end. Please note that some of this is not relevant to screw in ND filters if this is what you use.

The standard Cokin P mount bracket (3 slots) would be visible with my K5 and Sigma 10-20 at the widest focal lengths. This was exacerbated with the addition of a standard width CPL. The vignette would disappear as I zoomed to the longer focal lengths but then why have a 10mm focal length?

I replaced the standard Cokin bracket with the wide ange version that is thinner and accomodates only one filter. This fixed the issue when mounted directly to the lens, however if I used the CPL and the wide angle Cokin bracket it would still vignette under 12mm. An improvement and the need for me to work around the limitations of the kit I had.

There are also thinner CPL filters available, the CPL I recevied with a lens purchase in 82mm is half the thickness of the standard versions I have in 49/58 and 77mm.

If you're experiencing the vignetting from filter depth some of the above may be of use, though I do think the uneveness a CPL can create with wide lenses needs to be checked too. Rotating the filter whilst pointing at a blue sky 90 deg to the sun will clarify whether this issue is relevant to your experience. http://www.cambridgeincolour.com/tutorials/polarizing-filters.htm

A note on my Cokin wide angle filter bracket. I bought the 82mm adapter for the 21mm lens I wanted to fit the filters to and found that the screw in adapter was rather thick. When I mounted the bracket to the lens I realised the adapter circumference is too large for the P mount bracket causing it to bow in resulting in vignetting which is particularly noticeable on the K-1. I will need to replace my wide angle ND filters to use with this lens.

Please disregard if the above is not relevant or info you're already across, if not I hope this was of assistance.

Tas
07-03-2016, 09:56 PM   #6
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QuoteOriginally posted by MrMontana1889 Quote
Hello All,

I recently upgraded from the K-30 to the K-1 including the purchase of the HD Pentax-D FA 28-105 mm lens.

Since the lens is a larger diameter than my other lenses I also purchased a [circular] polarizer and ND filter kit.

What I've noticed recently is that with the polarizer and an ND filter on the lens it creates a vignette in the top-left and top-right corners of the image. But it doesn't seem to create one in the bottom-left and bottom-right corners unless it just happens to be the composition of the photo.

This didn't happen with my K-30. On my K-30 I used the polarizer and ND filter together all the time (especially with my waterfall photographs).

Am I doing something wrong with the new lens that is causing this vignetting? Could it be that my ND filter is not screwed on correctly?

Any thoughts and ideas on how to avoid this would be greatly appreciated. I leave for Montana in a week so I'm hoping to figure this out before I leave.

Thanks!

MrMontana1889
(Kris)
Sometimes variable ND filters can cause some strange effects especially combined with CPL... If it was in all 4 corners I will say that you need thinner filters but also maybe you did not notice vignette on the bottom. The best way is to check again with lens pointed to blank white wall or blue cloudless sky and shot the widest angle (28mm) at different apertures and see if the vignette starts to occur at some point and gradually worsens with another aperture than for sure it is that you need thinner filters but if you have the same effect on all apertures than is something else.

Anyway your ND filter should be screwed correctly.

EDIT: also if you use the graduated ND filter that behaviour is normal

Last edited by RAART; 07-03-2016 at 10:18 PM.
07-04-2016, 06:46 AM   #7
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Thank you everyone for the wonderful and useful responses.


Let me clarify some assumptions.


I am using a circular polarizer, 62mm in diameter. In the case I described I am using an 1.2 non-variable ND Filter to help darken the composition to allow for a longer shutter speed (to help "smooth" the water of the waterfalls that I shoot).


The vignette seems to happen most often at 28mm focal length but I did take some photos yesterday at 40mm focal length and there was some slight vignetting at the top-right and top-left corners (not as bad as at 28mm).


When I shoot with only the polarizer there are no darkened corners and everything looks good. However, when I put the 1.2 ND Filter on top of the polarizer the top-left and top-right corners darken - I mean really, really darken. This *never* happened with my K-30 in the 3 1/2 years that I used it. Now, it is possible that the thickness of the new polarizer I bought could be "just" thick enough so when I add the ND Filter it adds the vignetting but I just don't see that happening. It is a standard circular polarizer made by Tiffen purchased online at Adorama. The ND Filter Kit was purchased at B&H Photo (it was out of stock at Adoroama)


Anyway, I will see if I am screwing the filter on incorrectly. Hopefully it is as simple as that.


I've uploaded one of the photos I took from yesterday showing the vignetting in the upper left/right corners. The photo is only to demonstrate what I am seeing.


Thank you again for all your comments and kind words.


MrMontan1889
(Kris)
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07-04-2016, 08:18 AM   #8
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IMHO This is the edges of the filter whoever is the second one. The filter is not sitting strait must be on an angle. If the filter is not screwed all the way in or doesn't allow to get screwed, it is on the angle then the threads are damaged or not machined properly.

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