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Author Topic: Mamiya 28mm Lens filter question  (Read 15029 times)
Paul2660
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« Reply #40 on: April 12, 2008, 09:18:03 AM »
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Don, thanks for the images.  BTW, what did you use to cut the extra lens cap.  You picks showed what I was afraid of, the plastic will shatter when you try to cut it.

Also with it on that way, do you get good tension on the lens shade, such that if you have the camera pointed down, the rig won't slide off?

I never heard back from Tiffen, they don't seem interested.  The glass size needs to be 3mm thick to fit inside the X-Pro holder.  The schneider 5.65 x 5.65 is about 4mm thick but also too wide.  I also realized if I had mine cut I would have sharp edges and it would just make for more work.  

Paul C
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Paul Caldwell
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« Reply #41 on: April 12, 2008, 10:06:30 AM »
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I used a dremel and a plastic cutting wheel to cut the lens cap.  The plastic did not shatter, what you see is plastic shavings made from the cut.  I took my time cutting the very edge of the cap off but even with that I still have the shavings, afterwards I smoothed the shavings down.  It may not look pretty but it works.

I put the cap back on the same way it would be if the front were one it, that way the inner bevel is holding on to the lens and remains nice and tight.  I don’t think there’d be a problem with the lens pointed down with the frankenlibby design on as it is a tight fit.  I’ve played with the filter holder and circular filter on the lens and can move each freely without disturbing the setup.  The screws are leaving a mark in the plastic and I think I might just drill a hole so that I can fit the adapter back in the same place each time.  

I still think that I might attempt to permanently mount a ring to the end of the plastic thus eliminating the need of the adapter – might attempt that later today.

All in all this winds up being relatively sturdy with the adapter and filter holder in place, just a bit awkward with the four large screws protruding that’s why I want to try just a normal ring and filter holder….stay tuned.

BTW – no sharp edges after the cut.

Also as my wife just reminded me – cut outside as the smell of heated plastic is not all that pleasant!

don
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Don Libby
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« Reply #42 on: April 12, 2008, 11:24:37 AM »
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Not so good news to report.

Attempted to superglue a ring to the cap without success, just wouldn’t stick to each other.

Vignetting….

When I looked through the lens yesterday afternoon I had the filter in place thus I failed to see any vignetting.  I had the camera outside this morning and looked thru the lens with just the lens cap/filter holder on – the lens cap produces vignetting.  While most of the vignetting is outside of the P30’s crop lines there still some that goes into the image area thus making this solution for P30 only and not for P45’s.

I’ve included four images.

View without device                    View with device only
[attachment=6071:attachment]                  [attachment=6072:attachment]
View with circular filter                    Cropped image
[attachment=6073:attachment]                  [attachment=6074:attachment]

While I think I can use this in a very limited way I’m now retiring from this endeavor and more than willing to let others pick it up from here.  

don
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Paul2660
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« Reply #43 on: April 12, 2008, 03:12:33 PM »
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the lens cap must be vignetting where the tulip dips are.  

However can you test one thing?  Tim reported that the Cokin CL-PL did the same thing as your image showed, the hard vignetting around the corners.  Can you try the lens cap mount and Universal adapter without the CL-PL and see if you still see the vignetting?

Thanks
Paul C
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Paul Caldwell
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« Reply #44 on: April 12, 2008, 04:10:31 PM »
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Quote
the lens cap must be vignetting where the tulip dips are. 

However can you test one thing?  Tim reported that the Cokin CL-PL did the same thing as your image showed, the hard vignetting around the corners.  Can you try the lens cap mount and Universal adapter without the CL-PL and see if you still see the vignetting?

Thanks
Paul C
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You're correct, it's being caused by the lens cap.  Image #2, shows the vignetting occuring with the lens cap, universal adapter and filter holder on.  Image #3 includes the CL-CP.  Image #4 shows the usable crop.

I'll be at the Gila Cliff Dwellings next week and will try this gizmo out there.  I know I'll have vignetting but I want to see what the usable image might be.  

don
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HarperPhotos
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« Reply #45 on: April 12, 2008, 04:29:07 PM »
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Gidday,

Got the New Zealand rep Tim to ask Mamiya Japan if they were going to make a filter attachment for the Mamiya 28mm and the reply was NO.

Cheers

Simon
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Simon Harper
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ternst
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« Reply #46 on: April 13, 2008, 03:48:43 PM »
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The polarizing filter rig that I made up for my 28mm with P-45+ works fine with no vignetting. I used the Cokin x-pro holder with universal adapter. I removed the four screws from the adapter, and then cut out a foam ring that fit snugly over the lens hood. The outside of this foam ring fit snugly inside the universal adapter ring, and then I taped them together - this way I did not need to use those screws at all.

I put four small bits of velcro on the outside end of the filter holder, and matching velcro strips on the inside side of the Schneider 5.6" x 5.6" polarizer. When I need to use the filter I simply slip the Cokin holder over the lens (I also added some tape on the lens hood to act as a stop for the filter holder), then stick the heavy piece of glass onto the front of the filter via the velcro. The rig will rotate just fine and there is no vignetting. There are some reflections from the top corners of the filter, but I simply lay the filter case on top of the lens to cover it up and it is fine. I've been shooting a bunch of waterfalls in Arkansas this week and have used this setup a dozen times or so with no issues.

Tim Ernst in Arkansas
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Don Libby
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« Reply #47 on: April 13, 2008, 05:24:34 PM »
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Quote
The polarizing filter rig that I made up for my 28mm with P-45+ works fine with no vignetting. I used the Cokin x-pro holder with universal adapter. I removed the four screws from the adapter, and then cut out a foam ring that fit snugly over the lens hood. The outside of this foam ring fit snugly inside the universal adapter ring, and then I taped them together - this way I did not need to use those screws at all.

I put four small bits of velcro on the outside end of the filter holder, and matching velcro strips on the inside side of the Schneider 5.6" x 5.6" polarizer. When I need to use the filter I simply slip the Cokin holder over the lens (I also added some tape on the lens hood to act as a stop for the filter holder), then stick the heavy piece of glass onto the front of the filter via the velcro. The rig will rotate just fine and there is no vignetting. There are some reflections from the top corners of the filter, but I simply lay the filter case on top of the lens to cover it up and it is fine. I've been shooting a bunch of waterfalls in Arkansas this week and have used this setup a dozen times or so with no issues.

Tim Ernst in Arkansas
[a href=\"index.php?act=findpost&pid=189281\"][{POST_SNAPBACK}][/a]

Tim

I showed you mine how 'bout a couple images of yours?

don
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Paul2660
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« Reply #48 on: April 14, 2008, 11:12:20 AM »
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The foam works, like Tim pointed out.  This keeps most of the reflected light from coming back in around the opening where the screws are.  I used mini-cell, gray, most common in whitewater kayak walls.  I cut out a ring of the foam based on the diameter of the Universal adapter, then made an inner cut out for the lens shade.  This works, fine the mini cell has a good grip and holds the X-Pro on well.   Then mounting the Glass sheet from Schneider is the final step.  I have yet to find a really quick way to get the mounting of the glass, but Velcro sounds like a good idea.   You will still need to cover the top of the rig as the glass sheet pulls in reflections from the top, I used a dark cotton cloth for that.   Over time Mini cell will harden so it will need to be replaced over time.

Tim, did you use the Velcro self adhesive style?  It gets a good enough grip I guess.  

I also found out that most of the time, when I had the rig 100% polarized, the sheet wasn't lined up square, most times it was lined up at an angle from 90 degrees.  

In shooting over the weekend, I never had a great feeling that the sheet wasn't going to fall off the way I was securing it, so I need to move to the Velcro.

Paul C
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Paul Caldwell
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« Reply #49 on: April 14, 2008, 12:09:24 PM »
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Here are a couple shots from my setup. The self-stick velcro works great on the holder but I've already had a couple come off from the glass so I keep a some already cutup in my pocket. I pointed it down over a 110' cliff the other day and just held my breath...
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Paul2660
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« Reply #50 on: April 14, 2008, 12:14:46 PM »
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Tim,  

I had been using rubber bands to hold the glass in place.  The ones that come on broccoli, short blue or red ones that are a tad wider than normal rubber bands.  This combined with Velcro would be a good safe guard to the sheet falling off.

Paul
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Paul Caldwell
Little Rock, Arkansas U.S.
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Don Libby
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« Reply #51 on: April 14, 2008, 01:52:49 PM »
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Tim

Thanks for posting the images; you did a much better job of it than I did.  I like the idea of using a foam ring instead of the lens cap however it appears that the way it mounts (further back) eliminates the use of a CL-PL.  Can you move the ring closer to the leading edge in order to mount the CL-PL and not get vignetting?

I’m headed to the Gila Cliff Dwellings to test my contraception out; this will be the last chance to test prior to the Alaska trip in May then it’ll be too late.

don



Quote
Here are a couple shots from my setup. The self-stick velcro works great on the holder but I've already had a couple come off from the glass so I keep a some already cutup in my pocket. I pointed it down over a 110' cliff the other day and just held my breath...
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ternst
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« Reply #52 on: April 14, 2008, 01:56:22 PM »
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What is the CL-PL? If that is the round polarizer, then yes, you can mount it either direction, you would just need to position the holder however you need to and make sure it is snug - mine is set up so that it goes all the way back, but I also use a sunset filter in one of the slots and just don't push the holder back as far and it works fine. You cannot use the round polarizer with the p-45 back, but you have the p-30, right? I don't know how it would work with that one.
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