September 23, 2014, 12:50:49 PM

Author Topic: Strange Lens Flare (Sigma 35mm + MRC filter)  (Read 4012 times)

mrsfotografie

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Strange Lens Flare (Sigma 35mm + MRC filter)
« on: January 02, 2014, 01:38:35 AM »
FWIW I noticed the Sigma (with a B+W MRC filter on it) is sometimes prone to flare from off-scene light sources, as shown in these pictures. The fact that the flares are all on the right hand side is a coincidence, but all the flares are confirmed to be from bright street lights just outside the frame. I haven't seen any occurrence of the lens flare in horizontal position.

These shots were all taken hand held, with (near) open aperture (<f/2.5) and the lens hood is on. The camera is gripped but obviously the lens extends beyond the grip. I'm not sure that I like this effect, and it is something I may want to avoid in the future but on the positive side it does have something reminiscent of the anamorphic lens(flare) effect as seen in some movies.
Does anyone recognize this flare, is it something to do with the MRC filter? All of my UV/clear filters are B+W but this is probably the ony one I have with a multi reflective coating (MRC). Cheers.
« Last Edit: January 03, 2014, 03:33:31 PM by mrsfotografie »
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Strange Lens Flare (Sigma 35mm + MRC filter)
« on: January 02, 2014, 01:38:35 AM »

dgatwood

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Re: Strange Lens Flare (Sigma 35mm + MRC filter)
« Reply #1 on: January 02, 2014, 10:19:47 AM »

It kind of looks like it might be dust somewhere.  Otherwise, no idea.

mrsfotografie

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Re: Strange Lens Flare (Sigma 35mm + MRC filter)
« Reply #2 on: January 02, 2014, 10:59:34 AM »

It kind of looks like it might be dust somewhere.  Otherwise, no idea.

I'm sure it's not dust ;)
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Re: Strange Lens Flare (Sigma 35mm + MRC filter)
« Reply #3 on: January 02, 2014, 11:16:29 AM »
Have you used that particular filter on a different lens to narrow it down?
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mrsfotografie

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Re: Strange Lens Flare (Sigma 35mm + MRC filter)
« Reply #4 on: January 02, 2014, 11:23:14 AM »
Have you used that particular filter on a different lens to narrow it down?

No... I was hoping someone here might recognize the phenomenon.
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Re: Strange Lens Flare (Sigma 35mm + MRC filter)
« Reply #5 on: January 02, 2014, 11:44:42 AM »
I have the Sigma 35 and use it with a B/W XS Pro Clear MRC with no issues.
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tolusina

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Re: Strange Lens Flare (Sigma 35mm + MRC filter)
« Reply #6 on: January 02, 2014, 12:42:43 PM »
Have you tried these type scenes both with and without the filter?
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Re: Strange Lens Flare (Sigma 35mm + MRC filter)
« Reply #6 on: January 02, 2014, 12:42:43 PM »

mrsfotografie

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Re: Strange Lens Flare (Sigma 35mm + MRC filter)
« Reply #7 on: January 02, 2014, 12:53:25 PM »
Have you tried these type scenes both with and without the filter?

No... this was the first time I used the lens in a situation like this. It may be a complete coincidence but I do have about 1 in 15 shots from this session that show this lens flare.
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dgatwood

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Re: Strange Lens Flare (Sigma 35mm + MRC filter)
« Reply #8 on: January 02, 2014, 04:57:13 PM »

It kind of looks like it might be dust somewhere.  Otherwise, no idea.

I'm sure it's not dust ;)

Never mind.  I thought you were talking about the sparkles, which I now realize are, in fact, Christmas lights.  :D  This is the danger of looking at the photos on a cell phone.

The horizontal line at the right edge looks almost like a light leak to me.

mrsfotografie

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Re: Strange Lens Flare (Sigma 35mm + MRC filter)
« Reply #9 on: January 02, 2014, 05:58:25 PM »
The horizontal line at the right edge looks almost like a light leak to me.

You're right, I had thought about this but the flare is not always in the same place, and I cross checked with other photo's from this series that give a better idea of the street layout- it is almost definitely from light sources (bright street lights) just outside the frame. I had thought about light leaking into the viewfinder, but I had my eye in front of it so that may rule it out. The thought had occurred to me that the light may hit the filter and then be bent by the convex front element to produce the flare.

I just did some tests in my living room with the Sigma mounted on my 5D Mark III, and I was able to reproduce the effect but not quite to the same extent as it was on the street with my 5D Mark II. Again, holding the camera by the grip (with the top of the camera facing left) and with a bright light just on the right edge of the frame, the flare occurs. Turning the camera 180 degrees and taking the same shot eliminates the flare! I shot a f/1.4 and 1/30 sec to simulate the street photo's. I can clearly see a bright sliver in the viewfinder when taking the shot. Depending on the orientation the shape of this sliver changes ( it is much wider when shooting a vertical frame with the top of the camera facing right).


Now this got me thinking... it may be stray light hitting the mirror? This would explain why the flare occurs only in one orientation, and differences in the MkII and III construction may explain why the effect is greater on the Mk II. Hmmm.... ::)

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Re: Strange Lens Flare (Sigma 35mm + MRC filter)
« Reply #10 on: January 02, 2014, 06:00:30 PM »
Maybe you did and I missed it but did you perform the same indoor test without the filter?
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mrsfotografie

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Re: Strange Lens Flare (Sigma 35mm + MRC filter)
« Reply #11 on: January 02, 2014, 06:06:22 PM »
Maybe you did and I missed it but did you perform the same indoor test without the filter?

Sorry, but no. I was looking to do a test in the same conditions just to rule out the body. I always shoot with filters and prefer to leave them on to protect the front element. The effect is markedly less on the 5D MkIII (almost unnoticeable and difficult to reproduce).  I'm fairly confident now that it is something to do with the mirror, not the filter because the orientation of the body is important (and I checked the filter- it's clean and in perfect condition).
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Re: Strange Lens Flare (Sigma 35mm + MRC filter)
« Reply #12 on: January 02, 2014, 06:09:17 PM »
So it's the lens. has it taken a hit? Are there any noticeable dings or mars along the mount side? Run your finger along the EF mount.
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Re: Strange Lens Flare (Sigma 35mm + MRC filter)
« Reply #12 on: January 02, 2014, 06:09:17 PM »

mrsfotografie

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Re: Strange Lens Flare (Sigma 35mm + MRC filter)
« Reply #13 on: January 03, 2014, 04:29:28 AM »
So it's the lens. has it taken a hit? Are there any noticeable dings or mars along the mount side? Run your finger along the EF mount.

The lens is pristine, brand new. Nothing wrong with it ;)
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Re: Strange Lens Flare (Sigma 35mm + MRC filter)
« Reply #14 on: January 03, 2014, 06:40:49 AM »
That's why I always use the lens hood, even there is no sun....
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Re: Strange Lens Flare (Sigma 35mm + MRC filter)
« Reply #14 on: January 03, 2014, 06:40:49 AM »