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Lee Big Stopper and Zeiss 21mm - Light leak


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#1 dgc

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Posted 01 April 2014 - 18:24

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Has anybody had similar problems with possible light leaks using long exposures with the Lee Big Stopper (Seven5 system) on Zeiss lenses. Following a search on this forum I have found that early 21mm f2.8 could be prone to light leaks; my 21 was bought in January 2014.

I have tried the Big Stopper with several combinations of adapter/ no holder, no adapter/ no holder, etc and I thought I had it nailed with the 46mm adapter being the problem, however, it does not affect my Zeiss 35mm as much and the light leak appears to start a few mm above the bottom of the image, which to me does not suggest that the adapter is the sole problem.

The first two images show the 21mm with my M240 and the 3rd image 21mm with my A7; the latter showing possible internal reflection in the bottom left corner.

Any thoughts or pointers would be welcome.

David

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Edited by dgc, 01 April 2014 - 18:26.


#2 jankap

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Posted 01 April 2014 - 23:15

There must already be a thread with a similar problem. Please search with "big stopper".
Jan
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#3 farnz

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Posted 02 April 2014 - 00:45

In other threads it was shown that the flange mount is often the where the light leaks probably owing to mechanical tolerances. The fix is inexpensive and simple although a little undignified for some: a black scrunchy at the base of the lens.

Pete.
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#4 dgc

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Posted 02 April 2014 - 08:58

I originally thought it was the same problem after doing a search but I have no light leak with my 39mm adapter and 50mm Summicron lens, it just seems to be when I use the 46mm adapter.

I do not think the Zeiss 21 and 35mm lenses are anywhere near as heavy as the Noctilux, but all answers do seem to suggest the problem is at the flange mount.

Thanks anyway.

David

Edited by dgc, 02 April 2014 - 09:14.

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#5 MarkP

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Posted 02 April 2014 - 10:55

Hi David,

the leaks at the bottom right-hand corner of the image with prolonged exposure in daylight (especially with the camera in direct sunlight) are very typical of the light leak at the flange - at about 2:00 under the rangefinder window. A black hair scrunchie around the lens mount is the cheap fix. The 3rd image with the leak at the bottom left hand corner is less typical unless the sun was shining directly onto the other side of the flange.

This issue is discussed in great detail in the two threads below:

http://www.l-camera-...re-issue-2.html

http://www.l-camera-...hot-7000-a.html

In my experience the Zeiss lenses may be a bit more prone to this because the outer lens mount ring being recessed.

To test the flange yourself you need a very bright torch and run it around the lens mount flange on a very long exposure (see the threads above).

Edited by MarkP, 02 April 2014 - 11:06.

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#6 250swb

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Posted 02 April 2014 - 12:44

The first two images show the 21mm with my M240 and the 3rd image 21mm with my A7; the latter showing possible internal reflection in the bottom left corner.


It is now a well known problem, and not restricted to the M240, but also the M9 and the MM. It occurs in the same place in the frame for everybody, and with almost any lens. The light enters where the cut out on the flange for the focus cam is situated. So it is not unique to your 21mm ZM. In the third photo it looks like your A7 is doing something similar but the light is coming in from a different angle. Something wrapped around the base of the lens solves it, I use a neoprene band with Velcro on each end made from a cut down mountain bike headset boot, but a scrunchy is as good or even a lens cloth can help if it isn't going to get blown away.

Steve
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#7 MarkP

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Posted 02 April 2014 - 13:19

I missed that the 3rd photo was on the A7 until I read Steve's post. These are all flange light leaks
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#8 Nick_S

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Posted 02 April 2014 - 13:33

Now that Voigtländer lenses have a milled recess on the outer part of the mount (to allow the addition of 6-bit codes that don't rub off so easily), I wonder whether their lenses are more prone to light leaks.

Nick

Edited by Nick_S, 02 April 2014 - 13:43.

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#9 dgc

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Posted 02 April 2014 - 15:03

The last thing I wanted to do was re-ignite the big stopper debacle; all my testing suggested the adapter was the culprit especially as the problem is not apparent with some of my lenses. Clearly, it is a flange light leak.

I understand the Fuji X cameras are also prone to this type of light leakage - not many cameras appear immune to this basic design flaw. I will stop at that before I start repeating what has no doubt been said numerous times before in other threads.

Thanks again.

David
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