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Advise on lens hood dimensions for Zeiss S-Planar 74mm

 
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Joco



Joined: 28 Dec 2016
Posts: 29
Location: Amsterdam

PostPosted: Mon Dec 25, 2017 6:17 am    Post subject: Advise on lens hood dimensions for Zeiss S-Planar 74mm Reply with quote

I was recently very lucky to find a Zeiss S-Planar 74mm. I will be using it on a Novoflex bellows for focus stacking.

Important to note is to this bellow I use the PROshift+ which enable the camera to be moved 10 mm to the left and right. The resulting images I stitch as panorama. If I am not mistaken the size of the image circle would be 44xx36mm (I haven't tried horizontally which would yield 56 x 24 - knowing myself I will give that a go one day..... :-) ).

With my S-Planar 100mm f4 (for Contax bellows) I always use a polarization filter and lens hood, which at least in some case is very beneficial. I'd like to do the same for the 74mm.

The lens has no filter thread, but I found a rubber table leg covering which fits very snug on the 74 and my thought was to glue a step up ring to this. That would than fit a pol filter on top of which a Heliopan (there are much cheaper alternative, but I like these) lens hood can fit.

What I can't get my head around is what dimensions these parts should have, without causing vignetting. I could obviously step up to 55mm and use the hood & filter I use for the 100mm, but a smaller diameter would be more practical.

Below a picture of the setup and an experiment with a flower.



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enricosavazzi



Joined: 21 Nov 2009
Posts: 1066
Location: Stockholm, Sweden

PostPosted: Mon Dec 25, 2017 6:51 am    Post subject: Reply with quote

Unfortunately the Zeiss S-Planar 74 mm does not have a filter thread (it was meant for duplicating 35 mm film).

The closest thing to a lens shade that I found to work is a black plastic 35 mm film canister, which has the right inner diameter to fit onto the front (and also the rear) of the lens barrel. Cut the canister in two and you get a lens shade (the open half of the canister) and a lens cap (the half of the canister with the bottom). Drill a 1 mm hole near the bottom half of the canister to let air escape while fitting the lens cap onto the lens.

You can also use the cap of the canister as a lens cap on the top half of the canister when mounted on the lens as a lens shade.

Of course it may not be easy to find a 35 mm film canister these days. The last I saw was several years ago.

PS - I use this lens at 1x or higher (up to 1.7x works for me) on Micro 4/3, so I do not need to worry about vignetting with the film can used as a lens shade. APS-C also worked with this lens shade. If you use full frame it may be a different thing. I can't help you with mounting a filter or polarizer, but as long as you find something that fits onto the lens barrel, the rest is simple.

PPS - This lens is designed for work at 1x. I did not test it on sensors larger than APS-C. YMMV at different magnifications and larger sensor sizes.
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Joco



Joined: 28 Dec 2016
Posts: 29
Location: Amsterdam

PostPosted: Mon Dec 25, 2017 7:13 am    Post subject: Reply with quote

Thanks ES - great tips on the use of a film cannister! I have a photo shop close by that still does some film work so they may have something for me.

My (virtual) sensor size is indeed even bigger than full frame, so vignetting is more of a concern. The lens itself does seem to cover this, based on my first experiments.
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dickb



Joined: 05 Jul 2010
Posts: 129

PostPosted: Wed Dec 27, 2017 12:51 pm    Post subject: Reply with quote

Film canisters tend to be quite shiny on the inside, for a lens hood you may want to line it with protostar/doodlebug black flocked paper or plastic. The size of the barrel of the S-Planar is just under 30mm, maybe a filter step down ring to 30mm makes a connection to a larger lens hood if needed.
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Joco



Joined: 28 Dec 2016
Posts: 29
Location: Amsterdam

PostPosted: Wed Dec 27, 2017 1:05 pm    Post subject: Reply with quote

Thanks Dick - great point on the shiny-ness of canisters as well as rubber.

A step down (or up depending from what side one is looking) is my plan - the question is - to what diameter?

I.e. which diameter would be safe to step up to and add a hood without vignetting?

There should be a formulate to calculate?
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dickb



Joined: 05 Jul 2010
Posts: 129

PostPosted: Wed Dec 27, 2017 1:31 pm    Post subject: Reply with quote

Ideally, a lens hood cuts out all the light you don't need for your image. So if you have a virtual 44*36mm sensor and you image at 1:1 magnification, ideally you would have a rectangular lens hood flaring out to 44*36mm, touching the subject. In practice, the lens hood is normally shorter and round. In this case, the maximum diameter for a round hood would be 57mm. As you use a shorter hood, you can get away with an increasingly narrow diameter.
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Joco



Joined: 28 Dec 2016
Posts: 29
Location: Amsterdam

PostPosted: Thu Dec 28, 2017 2:31 am    Post subject: Reply with quote

Hi DickB - thanks that's really great advise. So straightforward I almost feel silly I haven't thought of it myself.

So I need to test what image circle this lens has at a magnification I expect will be the maximum (1:2 I think), determine lens to object distance (circa 110 mm) and then all all variables are known to calculate.
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Joco



Joined: 28 Dec 2016
Posts: 29
Location: Amsterdam

PostPosted: Sat Jan 13, 2018 7:35 am    Post subject: Reply with quote

Parts finally came in - they are a bit specific so it takes longer.

Per dickb's advise (much appreciated!) I chose a 30,5 to 40,5 step up ring, 40,5 pol filter and 40,5 lens hood, all Heliopan.

The parts are connected to the lens using a rubber chair leg cover which I happened to have. Of which I cut a small piece. It fits around 30mm snugly.

I did not have time to test yet and the weather is not great, so waiting for that.

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Joco



Joined: 28 Dec 2016
Posts: 29
Location: Amsterdam

PostPosted: Mon Jan 15, 2018 11:09 am    Post subject: Reply with quote

And here's a shot with the new setup. Very detailled.

Pano of 3 stacks (should have stacked a bit deeper)

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