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Arri 435ES - Vignette


Paul Mortlock

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Im getting a vignette on the 435ES from a rehoused canon FD 20mm - Obviously a lens designed for 35mm stills and should easily cover.

Both on video assist and in the viewfinder.

Other focal lengths seem to be better 24/35/55/85 all good.

What am I missing? Please be gentle if I am having a brain fart.

 

Paul

IMG_7834.jp2

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Curious..

Are you using a mattebox? Could there be a fault with the re-housing? It's vignetting quite far into the right side. Got a photo of the lens?

Can you check the image circle of the lens itself, by holding it towards a window with some white paper held behind it, to check if it makes a circle big enough to cover full frame? Or take it to a rental house with a service department who have a lens projector and ask them to check it quickly.

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1 hour ago, Paul Mortlock said:

Not using an MB

Lenses look just fine on my S35 Amira. Its a TLS rehoused 20mm I have used many many times on digital.

I can jump into PV to have the lens projected, but as its fine on the Amira i'm thinking its not the lens.

 

Cheers,

 

P

IMG_7835.jp2 166.13 kB · 2 downloads


Well that’s really strange..

If all the other lenses are OK then there’s nothing wrong with the camera. But the lens is fine on an Amira, so there’s nothing wrong with the lens. A gate mask is after the mirror so you would not see it in the viewfinder, as you say.

All I can think is that perhaps the 20mm rehousing is not compatible with film cameras, maybe it protrudes too far out the back and somehow the lens is cocking in the mount? Does it seem to lock off cleanly in the PL mount? Could something be fouling before it seats properly? Though I’d expect the image to be soft on one side if it was cocked..

I think you may need to take it to Panavision and see if they can look at the set-up, I have a feeling if a technician has the camera in front of them they could work out the issue. 

 

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did you test the lens also on actual film negative or just the viewfinder and video tap?

sometimes lenses may vignette more in the viewfinder than on the actual film if the rear element protrudes a lot (is close to the film plane) so that the light rays (image) on the edges of the frame come from a lower angle than with other lenses (for example retrofocus ones where the rear element is further away from the film plane) . this may show differently on the viewfinder than on the actual film depending on the ground glass design etc.  So I would definitely test it with actual film in the camera... if the lens was fine on the Amira then it will most likely be fine on the film too even if the viewfinder image has darker edges (typically film is fine with lower angle rays and they tend to be more of an issue with digital sensors which may reflect the edge rays more than film does if the ray angle is low. But optical finders can be anything and especially the older ones may be picky about the ray angle)

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Gavin Whitehust at TLS personally told me all the FD range is good with film cameras.

It locks off beautifully in the mount.

I'll take it to PV and have it projected. 

 

Will report back

Edited by Paul Mortlock
typo
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51 minutes ago, Paul Mortlock said:

 

Appo - 

No - Ive not shot a frame on the camera yet

Looking through the VF it portholes hard. Much harder than the picture from the video assist I posted in the first post.

 

Thanks

 

Paul

do the other lenses have the image circle centered on the ground glass and video tap? if so, then the mount on the lens side would be the problem. If the other lenses have similar style off center vignette, then there would be something wrong with the camera's gg setup.

I did not get the photo working previously but now when looking at it, it definitely seems something is off center. if the image has flat focus plane across the frame then it is more likely to be a camera gg centering problem I think. If the focus plane is tilted, then I would suspect the lens's mount to be the issue. 

the other lenses likely have larger image circle and thus it is more challenging to see if they are centered or not. A trick I like to use is to use a very bright flashlight to create flares with the taking lens and I can see from the flares where the optical axis of the lens is located on the groundglass image. I would test that with the other lenses if you have time, it is easy to see this way if the issue affects all the lenses (so that it would be a camera issue, not a lens issue) or just this 20mm one (which tells you that the lens has mount issues which can be corrected by collimating)

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I would definitely test the flare trick first to see where to optical axis of each lens is located on the ground glass (shine a bright flashlight to the lens and move the camera a little to all directions to see from the flare moves where the optical axis is situated on the gg image. The flare always goes from side to side via the optical center ) . after finding it for each lens, you can compare if the 20mm has different centering or not. If the optical center is on the same spot on the gg for all the lenses, then the issue is the camera and not the lenses and the 20mm just shows the issue more clearly because it has smaller image circle than the rest of the lens set (which don't show any issue until they flare or you move the camera a lot so that you see the off-center issue from the parallax )

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3 hours ago, aapo lettinen said:

..you can compare if the 20mm has different centering or not. If the optical center is on the same spot on the gg for all the lenses, then the issue is the camera and not the lenses and the 20mm just shows the issue more clearly because it has smaller image circle than the rest of the lens set (which don't show any issue until they flare or you move the camera a lot so that you see the off-center issue from the parallax )

Worth checking, but I doubt the lens/ground glass alignment could be that far off.

A 435 (like most Arri cameras) can be easily switched between Standard 35 and Super 35, which shifts the optical centre across by a few mm. It’s possible the camera mount is set to Standard 35 but the ground glass is Super 35, but given that the lens is full frame, the image circle should be well and truly large enough to compensate for such a relatively small displacement.

It’s physically impossible to shift the mount otherwise, and the ground glass position is pretty firmly set with only minimal lateral adjustment possible anyway.  

It’s easy to check the mount setting - if 1 is printed on the top right of the mount it is set to Standard, if it rereads 2 then the mount is set to Super. A ground glass should also be marked either S (Super) or N (Normal) or simply observe whether the frameline is offset within the groundglass area (Standard) or fills it evenly (Super).

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The 20mm is a recent conversion so I've described the issue to TLS and returned the lens for evaluation. They mentioned that there are a number of things in the rehousing process that could cause this. I guess the red herring is that it worked perfectly with s35 digital cameras.

The camera is S35 - no 2 in the top right of the mount.

 

Thanks all for your input thus far. The knowledge here is fantastic,

 

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