Question about c-mount lenses (and a hello)

[LyleBright]

Hello to all. I just found this site and am grateful that it exists.

I have some questions and admit that I am rather ignorant in these matters.

I have various cameras, all film cameras, and just one digital 4/3 format Olympus PEN. I got it to be able to attach the old c-mount lenses. I have a Meopta 20mm and a Cooke Kinic 25mm (which is really a lovely little lens for all the interesting bokeh).

I am soon to receive a Cooke 50mm Ivotal and a Dallmeyer 1.5 Anastigmat ...

But my question has to do with the 100mm Cooke lenses, and especially the very fast 2.0, which I understand is very desirable and very expensive.

When I search I come up with lenses adapted to '35mm cine' but I reckon this is not the same as c-mount? Or is it?

Is that what the 'c' in c-mount means?

Does anyone have a photograph of a Cooke 100mm 2.0 lens suited for use with an adapter for the micro 4/3rds format? If I could see one I think I could better understand.

Why is this lens to expensive in comparison to the 25mm and the 50mm? Just because it is rare and fast?

I understand that people are using the 25mm and 50mm Cooke and Dallmeyer lenses on the Black Magic video cameras, but for what are people using the 100mm?

It seems a long and specialized lens. Or, is it used by film makers? (Some of the results of a search pull up VERY expensive film camera lenses).

Please help me to gain some understanding here!

Sincere regards,

Lyle

[luisalegria]

I know little of cine uses, but two minor answers -

"c" is probably "cine", but that is hardly conclusive. "c-mount" means a specific, very common 25mm thread mount which was typical of 16mm cine cameras at one time, but it certainly wasn't universal, there were lots of 16mm camera systems that used entirely different mount systems. And "c" was not usual on 35mm (I would think this would vignette on many lenses).

There are a couple of dozen 16mm and 35mm cine lens mounts, and lenses were very often professionally converted from one to another to suit the clients needs.

Many vintage lenses, certainly any Cooke or Taylor, Hobson branded ones, have a collectors value beyond their utility value. Its not always or usually the case that these lenses are valued for their unique qualities. Rarity or celebrity count as much or more.

[calvin83]

Which 'Cooke 100mm 2.0' are you referring to?

[LyleBright]

That’s what I am unclear about. It was mentioned to me by a friend. I assume it to be a 100mm Cooke 2.0 lens with the 25mm mount that requires the cmount adaptor.

More information I do not have.

Again, this is unfamiliar territory for me.

I have seen numerous 4” c-mount f 4.0 lenses on eBay but no 2.0 4” lenses.

I assume 4” to equate to 100mm. That is, if a 1” lens is 25”. But I am in the dark about all of this.

As Claudius said ‘Give me light!’

[DConvert]

There are at least three variants of the c-mount, all using the same thread 1"-32tpi thread at different registrations.

Std C-mount is used for both Cine & TV systems with a number of different sensor sizes. registration about 17.5mm
CS-mount has 5mm less registration & is only used in small format TV systems
then there's Bolex H8RX with registration of 15.3mm (between the other two) only AFAIK used for cine film.

Sellers of CS-lenses have often described them as c-mount, but these are nearly always short focal length lenses.

[paulhofseth]

As the standard Cmount has a shorter flange to film plane distance, "back focus", the adapter needs to fit inside the M4\3 mount. This limits the use of very big aperture lenses if the rearmost part of their mounts does not fit inside the recessed bits of the adapter.

As with all photography, long lenses were occasionally needed for filming, so lenses even longer than 100mm do exist. !6mm film lenses were designed for a smaller image circle than required for m4\3, but the longer focal lengths will usually avoid serious vignetting.

p.

[LyleBright]

Thanks much for the help.

[visualopsins]

Welcome LyleBright

[kds315*]

There are larger format Cooke f2 100mm (4") lenses, it doesn't have to be c-mount.
I had one here: http://www.macrolenses.de/ml_detail_sl.php?ObjektiveNr=368
which was as Cooke Optics confirmed an early Speed Panchro



And I used it on a mft camera....until I got an offer from Asia I could not resist

[spleenone]

[DConvert]