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Taking lens for Anamorphic Shop Focus Module (FM Lens)


Kerrick Martin
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Hey everybody. Haven't been on here in a while since I can't remember my old login credentials (People may remember me as Danson Delta-40). At any, I have a favor to ask.

I need a specific taking lens that fits a whole bunch of criteria. Here's the rundown:

 

  • The FM Module creates a vertical "hazing" with certain lenses. I need a lens that does not do this.
  • 50mm-85mm
  • f1.8
  • Can fit on my canon 7D with EF adapter.
  • Have LOW barrel distortion
  • Adapter CAN'T have its own lens for allowing infinity focus.

I have gone through three lenses thus far, and none have fit my criteria

Nifty Fifty is too light and plasticy, plus for me it created that vertical haloing.

Zeiss 50mm zebra m42 was good, but its barrel distortion is too high, and although sharp all the way open at f1.8, the flaring would bounce light around and I could actually see a green cast of the iris blades if it wasn't completely open.

Canon 50mm F1.4 FD would be great, but no matter what adapter I use, it cant do infinite focus with FM module, is waaaaaay too soft because of that, and its the SSC version (Super Spectral Coating) so not so flarey goodness.

 

Anyone know lenses that fits these conditions? Bonus if it's under 200 :D

 

EDIT: heres a screen from a video I took with the FM module and the canon 50mm F1.4 FD SSC lens.50mm FD.jpg

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You'll have to restric even more, as many many lenses fit your criterias :D
http://allphotolenses.com/lenses/c_342063/p_1.html

I can recommend the M42 Fujinon 50/1.8 if you don't want any flares. You can go the obvious route of using an Helios-44 if you like flares. Anything in between should be good too (Super Takumars, Mamiyas, Yashikas, Zeiss', you name it !)
If you want reduced vertical "hazing", I guess a lens with a smaller front element and closer to the variable diopter of the FM is required, but I do not have experience with that)

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Forget shooting anything wider than f4 on any taking lens and expect to get no glow/smear/hazing highlight aberrations on the FM - or most of the other vari-diopter solutions out there. It is all due the single element design of these diopters - it is simply the optical limits of single element design/ coatings and the glass index used.

Olympus OM's are quite good for FM use - 85/100 mm are especially sharp when stopped down, but these lenses  (and many others) will cut into the oval bokeh when stopped down, due to the non-circular aperture shape that the iris blades. A better solution to this is to search older preset lens types - those that have 13-16 blades, which maintain a nice spherical aperture from f4 upwards.

If you want a list of lenses to try, there are many posts on this forum about such things.

(or just search 'preset lens' on ebay). 

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34 minutes ago, Hans Punk said:

It is all due the single element design of these diopters

I'm pretty sure that you need at least two elements to make a variable diopter ;) (The FM and Rectilux can be sharp at wider apertures than f/4 btw -> have a look at @Tito Ferradans's test http://www.tferradans.com/blog/?p=9238 of the FM module) 

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2 hours ago, Justin Bacle said:

I'm pretty sure that you need at least two elements to make a variable diopter ;) (The FM and Rectilux can be sharp at wider apertures than f/4 btw -> have a look at @Tito Ferradans's test http://www.tferradans.com/blog/?p=9238 of the FM module) 

I'm talking about the limitations of a non-cemented doublet (achromatic) diopter (vs the single element as with these vari-diopter designs) - the single element optics of these vari-diopters is a major cause of aberrations of image at wide apertures.

Having owned a FM and Core DNA, I can confirm that f4 is the stop where both focus solutions start to resolve the cleanest image on high contrast edges...especially when pushed on full frame. Sharpness 'performance' depends on your eyesight I guess.

BTW - Tito's FM that he did the test with used to be mine...so I know that lens particularly well :)

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SMC Takumar 50mm f1.4 with the filter ring and beauty ring removed.


This is full frame, so throwing out the crazy distortions, you're left with a nice sharp middle. That's where all the resolution is anyway.

Usable albeit dreamy at f1.4, it really starts to shine at f2 and below.

Under $200:
http://www.ebay.com/itm/Excellent-Pentax-SMC-Takumar-50mm-f1-4-Lens-M42-Screw-Mount-With-Hood-filter-/322273530314

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Quote

Forget shooting anything wider than f4 on any taking lens and expect to get no glow/smear/hazing highlight aberrations on the FM - or most of the other vari-diopter solutions out there. It is all due the single element design of these diopters - it is simply the optical limits of single element design/ coatings and the glass index used.

 

Its not about the max aperature. its about stopping down. higher aperture lenses tend to be sharper  at comparable F-stops to other, less light sensitive lenses. Also, besides the aforementioned issues, my zeiss 50mm was suitably sharp for me all the way open at f1.8 with no vertical hazing.

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4 hours ago, Hans Punk said:

I'm talking about the limitations of a non-cemented doublet (achromatic) diopter (vs the single element as with these vari-diopter designs) - the single element optics of these vari-diopters is a major cause of aberrations of image at wide apertures.

Having owned a FM and Core DNA, I can confirm that f4 is the stop where both focus solutions start to resolve the cleanest image on high contrast edges...especially when pushed on full frame. Sharpness 'performance' depends on your eyesight I guess.

BTW - Tito's FM that he did the test with used to be mine...so I know that lens particularly well :)

Awhile back I spent many weeks designing variable diopter systems, including simple 2-element designs using singlets, 4-element designs with achromatic doublets, and a few complex 5 and 6 element designs.  What I discovered was that the limiting aberration in every case was spherical aberration at close focus.  Surprisingly, using more complex designs has very little impact on that spherical aberration, and they have numerous drawbacks including excess cost, and larger size and weight.  It turns out that a simple 2-element variable diopter, such as the ones used in all of the Iscoramas is not such a bad solution at all.  They give fantastic results for distant objects, and only gradually reveal weakness as you focus close.  As an aside, the only thing that I found to reliably eliminate close focus spherical was to allow the elements to get very weak, but this is completely impractical because the elements get huge and the front element motion becomes BIG.

BTW, it doesn't make much sense to talk about f/#'s when evaluating single focus units because absolute pupil size is what really matters.  For example, you might get a terrible result when attaching the unit to a 200mm prime at f/4 because the pupil diameter is 50mm, and yet get a really nice result with a 24mm f/1.4 because the pupil diameter is only 17mm.

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@Brian Caldwell That makes perfect sense.

I've had very good results by 'choking' many of my taking lenses by inserting a fixed spherical aperture disc (relative to f4-5.6 to that lens' aperture size). This enables a non-cut oval bokeh, whilst effectively stopping the lens down. f/4 on 2x anamorphic is already a darn shallow depth of field to pull focus with for anything other than trees and sleeping cats.

The aberrations I've noticed on the FM and Core DNA at wide apertures seem to be more apparent to the edges of the image - highlight 'smear' seems to be more pronounced on the off centre area of the optic - where the curvature of the front element begins. Adding a +0.4 doublet Tokina often seems to help clean up these edge artefacts at wide apertures....albeit at the loss of enabling infinity focus. There also seems to be another artefact that I'm not entirely sure about - that there seems to be optic face to optic face reflection that can create highlight 'blobs' when the elements are separated by distance during focus. The FM (and apparently rangefinder) seem to have this 'blob' artefact which makes me think it might be a coating issue (internal face reflection?)....Pure guess mind you.

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2 hours ago, Kerrick Martin said:

 

Its not about the max aperature. its about stopping down. higher aperture lenses tend to be sharper  at comparable F-stops to other, less light sensitive lenses. Also, besides the aforementioned issues, my zeiss 50mm was suitably sharp for me all the way open at f1.8 with no vertical hazing.

I should have mentioned more that I was referring to Full frame performance of these focus solutions...which will always reveal the worse edge artefacts at wider apertures. You will most likely find a suitable taking lens for your APSC camera by experimenting (unfortunately like every single FM owner had to do). The FM seemed to be optimised for smaller than s35 sensor, so Brian's mention of pupil size makes good sense to also consider experimenting with lenses that have a smaller pupil diameter.  

 

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1 hour ago, Hans Punk said:

I should have mentioned more that I was referring to Full frame performance of these focus solutions...which will always reveal the worse edge artefacts at wider apertures. You will most likely find a suitable taking lens for your APSC camera by experimenting (unfortunately like every single FM owner had to do). The FM seemed to be optimised for smaller than s35 sensor, so Brian's mention of pupil size makes good sense to also consider experimenting with lenses that have a smaller pupil diameter.  

 

So much to learn. I did not know about this pupil thingy but I had my beliefs that the wider the front element the more the vertical hazing.

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12 hours ago, Hans Punk said:

I'm talking about the limitations of a non-cemented doublet (achromatic) diopter (vs the single element as with these vari-diopter designs) - the single element optics of these vari-diopters is a major cause of aberrations of image at wide apertures.

Having owned a FM and Core DNA, I can confirm that f4 is the stop where both focus solutions start to resolve the cleanest image on high contrast edges...especially when pushed on full frame. Sharpness 'performance' depends on your eyesight I guess.

BTW - Tito's FM that he did the test with used to be mine...so I know that lens particularly well :)

Great, thank you for these usefull pieces of information :)

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21 hours ago, Hans Punk said:

@Brian Caldwell That makes perfect sense.

I've had very good results by 'choking' many of my taking lenses by inserting a fixed spherical aperture disc (relative to f4-5.6 to that lens' aperture size). This enables a non-cut oval bokeh, whilst effectively stopping the lens down. f/4 on 2x anamorphic is already a darn shallow depth of field to pull focus with for anything other than trees and sleeping cats.

The aberrations I've noticed on the FM and Core DNA at wide apertures seem to be more apparent to the edges of the image - highlight 'smear' seems to be more pronounced on the off centre area of the optic - where the curvature of the front element begins. Adding a +0.4 doublet Tokina often seems to help clean up these edge artefacts at wide apertures....albeit at the loss of enabling infinity focus. There also seems to be another artefact that I'm not entirely sure about - that there seems to be optic face to optic face reflection that can create highlight 'blobs' when the elements are separated by distance during focus. The FM (and apparently rangefinder) seem to have this 'blob' artefact which makes me think it might be a coating issue (internal face reflection?)....Pure guess mind you.

Hi Hans:

Using a good diopter will definitely improve the closeup image performance of a single-focus attachment, since it allows the attachment itself to be used closer to its "zero aberration" infinity setting.  I'm not entirely sure what you are describing about the highlight blob ghosting effect.  Most single focus attachments use a plano-concave moving front element followed by a convex-plano stationary element.  The concave surface of the front element is normally very close in radius to the convex surface of the stationary element, and this could set up a pair of reflections that might cause the effect you are seeing.  Its also possible that a reflection from the sensor followed by a reflection from either or both of the plano surfaces can cause noticeable ghosting, although in this case I would expect sharply focused mirror-image type ghosts.  Regardless of the root cause of the ghosting, its appearance can be reduced, but not completely eliminated, by using better AR coatings.

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