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The weird aperture blades of Kern Switar POE 16-100


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#1 Matthew B Clark

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Posted 07 October 2017 - 04:07 PM

I suppose the title could be taken into a thousand directions...and that's ok! 

 

I picked up a Kern Vario-Switar POE 16-100 H16 RX zoom to match up with the bayonet mount of my S16 Bolex EBM, but after shooting a few tests (which seemed a touch "dark") I looked closely at the aperture blades on this lens...it appears there is something (could potentially be a blade stuck perhaps, or not?  Not sure...) that is very obviously protruding into the usually circular aperture opening. 

 

Here are some pics below that illustrate it a little more clearly.  Basically, it looks like a piece of a blade sticking out....but I know the mechanics of this lens are really extreme for a zoom in this price range, and lets just say, it isn't exactly "not-nuanced", particularly with regard to the relationship evertything has to have with Bolex's camera specs at the time these were produced. 

 

So I guess what I'm asking is, has anyone else with a POE 16-100 seen this wonky blade/object in theirs?  What exactly is it?  If it's normal, or requires some special operational workaround, please do let me know!  Like I said, my footage was a touch too dark, and even with plus-x reversal at 100 ASA indoors, it shouldn't have been THAT dark....so I'm wondering if this thing is an abnormality that is either blocking out light, or if it's maybe an entirely overlooked aperture sticking problem (I thought it was all the way open at 1.9....fairly darn....99.9% positive I looked at the blades open at each stop before testing). 

 

Anyway, with their 2-blade aperture system deposited into the back of what seems to me to be a wonderful zoom, this is certainly a goofy lens.  While the bokeh will no doubt be polarizing (get it....two blades hehehe) I actually love it, and it's RX balanced for the S16 bolex so.....I'm planning on making it work for me.  But I need it to work! 

 

Here are the pics attached...

 

 

 

Attached Images

  • zoomedzommyzoom.jpg
  • zommyzzzzzzzoom.jpg

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#2 Jean-Louis Seguin

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Posted 07 October 2017 - 05:35 PM

That little object is a small peak-in mirror that send light to the photocell. It's perfectly normal.
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#3 Matthew B Clark

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Posted 07 October 2017 - 11:37 PM

Thank you, Jean-Louis! Yes, I just tested out all apertures again, and they work. Its odd to think so hard about the dangers of bokeh shapes with this lens. It can literally stylize a background like a cheesy Photoshop filter! But its a good lens like I said, and sharp. Im learning to be careful with it. Ranging from normal bokeh wide open to perfect diamonds that almost become big clunky diamond and kite objects themselves at around f8. But its a useful bastard of a lens for my purposes. So... Its a strict diet of no bright backgrounds, shots with infinite depth of field, or all the way open when the bokeh actually stays round. Or....shoot casino commercials.
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#4 Jean-Louis Seguin

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Posted 08 October 2017 - 01:58 AM

The vast majority of super8 cameras have similar moving vane aperture systems.
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#5 Matthew B Clark

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Posted 08 October 2017 - 08:00 AM

Pairing this with the Kern Switar (or macro Switar) 10mm preset... to round out the focal lengths I need. But does the macro version affect S16 vignetting any better or worse than the normal 10mm? Ive read countless back and forth evidence about the preset vs. normal 10mm lens covering, but nobody mentions the differences between the macro design and normal. I believe both come in RX preset versions. And is collimation, particularly for these 16-100 and 10mm lenses much of an issue usually? I think Ive read some bad stories about the shorter focal lengths on RX lenses having trouble focusing due to inexact back-focus. These things have me the most nervous, because I want to make sure the lenses do their job.
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#6 Jean-Louis Seguin

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Posted 08 October 2017 - 11:13 AM

Trying to make this simple. Firstly, always focus a zoom lens with the aperture set to the maximum, in this case f/1.9.

On a parfocal zoom lens, which the 16-100mm is, when you're adjusting the focus, you're essentially focusing the telephoto end of the range. The focusing ring has little effect on focus at the wide angle focal lengths where sharpness is entirely dependent on the back-focus adjustment, which you as the user have no control over. If your images are unsharp at the wide setting, the lens needs to be properly collimated.

 

With short focus prime lenses, such as the 10mm, your first concern is whether the lens can give you sharp image of a object at infinity.

A maladjusted lens might not be able to focus at infinity, rendering infinity subjects unsharp. A lens can also come adjusted where it actually goes past infinity, where again the result will be unsharp. The latter is less of a problem if you're focusing using the ground glass. You will eventually find the sweet spot. To collimate a prime lens is to ensure that the infinity setting is precise and that the distance markings on the barrel match the actual distances you're focused at.

 

Most people describe vignetting in a subjective manner. To some, vignetting means obvious encroachment of the image circle in the area of the viewfinder. This could be described as hard vignetting. For others, any small difference in image brightness (darkening) in the corners compared to the centre will be described as vignetting. You could refer to this as soft vignetting. Technically, both of these lenses will vignette on super-16 to a greater or lesser extent, but for some the result is still considered acceptable.


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#7 Matthew B Clark

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Posted 09 October 2017 - 06:50 AM

Thank you, Jean-Louis. This is very helpful. I appreciate your thoughtful response.
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#8 Matthew B Clark

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Posted 09 October 2017 - 01:56 PM

Also, Jean-Louis...does the macro version of 10mm have a radically different close focus distance than the normal 10mm? I am feeling like I dont even really concern myself with the preset version as much as the ability to close-focus in some cases. But if its a difference between an 8-inch minimum focus or something like that, and some extreme 1-inch focus, I can live with that sort of thing. Again, if one hard vignettes more than the other, that would certainly impact the choice.

Edited by Matthew B Clark, 09 October 2017 - 01:58 PM.

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#9 Dom Jaeger

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Posted 09 October 2017 - 09:44 PM

There is no macro 10mm Switar, they all focus down to 8" or 0.2m. The front of the lens is already about 3" from the film plane, so min focus is 5' from the front of the lens


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#10 Matthew B Clark

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Posted 09 October 2017 - 10:22 PM

Thank you, Dom!

But I assume you meant 5-inches, not 5-feet, right?

Edited by Matthew B Clark, 09 October 2017 - 10:22 PM.

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#11 Dom Jaeger

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Posted 09 October 2017 - 10:57 PM

Man, everyone's a critic! Yes 5 inches :)
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#12 Matthew B Clark

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Posted 10 October 2017 - 08:52 AM

That smiley face is a little crooked too, Dom. Just kidding...I appreciate your thoughts and info on these lenses. They are very good lenses that I think probably nauseate most of you because they certainly have been talked about to death. So when someone brings them up, I know its like here we go....cringe but all the same, I really appreciate it.
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#13 Jean-Louis Seguin

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Posted 10 October 2017 - 09:35 AM

Actually, the preset Switar 10mm does focus closer than the old style.

The old style focusing ring goes through a roughly 180 degree movement and the minimum focusing distance appears to be around 5-6 inches. The preset focusing ring goes through almost a full 360 degree movement and the minimum focusing distance appears to be about an inch from the front of the lens.


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#14 Matthew B Clark

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Posted 10 October 2017 - 11:15 AM

Is that a radical difference for some shots? Or negligible in all but extreme circumstances?

I guess my most concerning point is about the differences in the way the two versions vignette...hard or soft vignetting....either way...if one vignettes less than the other on an H16 RX Bolex super 16 EBM....thats the one for me.
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