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Fun page comparing 17 classic 25mm C mount lenses
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Home Manual Focus Lenses  Cine lenses
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PostPosted: Sat Feb 22, 2020 5:09 am    Post subject: Fun page comparing 17 classic 25mm C mount lenses Reply with quote
Hi folks,
After taking stock, I realized I have 17 C mount cine lenses all around 25mm, so I decided to do a gallery comparing their rendering. Have a look here if interested

https://toby-marshall.com/galleries/bokeh-tales/a-comparison-of-the-bokeh-and-rendering-of-17-25mm-c-mount-16mm-cine-lenses/

Toby

[corrected Link Nov 2020]


PostPosted: Sat Feb 22, 2020 9:51 am    Post subject: Reply with quote
Like 1 Like 1 Like 1

Thanks, great ressource this is Toby!!


PostPosted: Sat Feb 22, 2020 12:09 pm    Post subject: Re: Fun page comparing 17 classic 25mm C mount lenses Reply with quote
kymarto wrote:
Hi folks,
After taking stock, I realized I have 17 C mount cine lenses all around 25mm, so I decided to do a gallery comparing their rendering. Have a look here if interested

https://toby-marshall.com/galleries/a-comparison-of-the-bokeh-and-rendering-of-18-25mm-c-mount-16mm-cine-lenses/

Toby


Like 1 Like 1


PostPosted: Sat Feb 22, 2020 2:33 pm    Post subject: Reply with quote
Absolutely interesting, but the remarks on Kerns RX lens should take into account that their distance to the film plane is different from the ordinary ones, so the ordinary c-mount adapters will give the wrong focus. The extra correction in their design to compensate for the paillard reflex prism should in principle make them better suited to the thick sensor-glass of the MFT cameras.

p.


PostPosted: Sat Feb 22, 2020 6:36 pm    Post subject: Reply with quote
paulhofseth wrote:
Absolutely interesting, but the remarks on Kerns RX lens should take into account that their distance to the film plane is different from the ordinary ones, so the ordinary c-mount adapters will give the wrong focus. The extra correction in their design to compensate for the paillard reflex prism should in principle make them better suited to the thick sensor-glass of the MFT cameras.

p.


Thanks for that! I will include that information; however this gentleman seems to differ with you on the point of backfocus. He says:


"Back Focus
The first thing to clarify is that the back-focus distance setting of RX and non-RX lenses is the same. In other words, both are designed to form an image 17.52mm behind the mount flange, which is the C-mount standard. You cannot simply "re-collimate" or "adjust the back-focus" of an RX lens to make it non-RX or vice versa.

Some confusion exists because the prism in a reflex Bolex acts to extend the light rays further back, so the "physical" distance between the mount and the film plane in a reflex H16 is actually 20.76mm, but the simple fact is that any C-mount lens fitted to a reflex Bolex will have its back focus distance extended back to this point."

Or did I misunderstand your point about getting wrong focus with normal C mount adapters? Mine, anyway,, allows focus past infinity with all my lenses, which is probably a deliberate choice by the manufacturer - acknowledging that people will be focusing via the sensor rather than distance scale - to make sure that people can achieve infinity focus. Certainly better to lose a bit of close focus rather than not being able to focus at infinity.


http://cinetinker.blogspot.com/2014/12/rx-vs-non-rx-lenses.html


PostPosted: Sat Feb 22, 2020 8:47 pm    Post subject: Reply with quote
sorry I was wrong about back focus difference, but maintain that thicker sensor glass might be favourable.

Paillards own presentation of their c-mount lenses for 16mm RX states 17,52mm on page 11 of their brochure me 111/668mm and ME116/26 ad RX9 clearly states a film plane to lens seat distance of o,690 inches. "like the C mount", but underlines like the 16mm brochure does, that they can only be mounted on the RX models, but that lenses longer than 50mm can be freely interchanged.

p.


PostPosted: Sun Feb 23, 2020 11:39 pm    Post subject: Reply with quote
@kymarto I get to a page with 404 page not found. Is the gallery taken down?


PostPosted: Thu Nov 12, 2020 8:50 am    Post subject: Reply with quote
blotafton wrote:
@kymarto I get to a page with 404 page not found. Is the gallery taken d
down?


Sorry I didn't see this. Here is the working link

https://toby-marshall.com/galleries/bokeh-tales/a-comparison-of-the-bokeh-and-rendering-of-17-25mm-c-mount-16mm-cine-lenses/
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