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JML 35mm f/1.4 with electronic shutter
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PostPosted: Tue May 07, 2019 4:03 pm    Post subject: JML 35mm f/1.4 with electronic shutter Reply with quote
I was so curious when I saw it. BINed in EBAY. When it arrived, I realized it has electronic controlled shutter/aperture. If anyone here has adapted similar lens, can I ask some help here for the following questions?

1. Is it easy to disassemble the lens to disengage the electronic shutter?
2. As it is a C mount lens, how much will it cover the full frame? I guess it will have an image circle.
3. I plan to have a C-M42 adapter, M42 to Nex focusing helicoid. What kind of helicoid should I use? There are usually three main ones for different focusing range.

The lens looks like this:

https://www.ebay.com/itm/RT-JML-OPTICAL-35MM-F-1-4-611-/401738784077

Thanks a lot for any information.


PostPosted: Wed May 08, 2019 7:36 am    Post subject: Re: JML 35mm f/1.4 with electronic shutter Reply with quote
vivaldibow wrote:
I was so curious when I saw it. BINed in EBAY. When it arrived, I realized it has electronic controlled shutter/aperture. If anyone here has adapted similar lens, can I ask some help here for the following questions?

1. Is it easy to disassemble the lens to disengage the electronic shutter?
2. As it is a C mount lens, how much will it cover the full frame? I guess it will have an image circle.
3. I plan to have a C-M42 adapter, M42 to Nex focusing helicoid. What kind of helicoid should I use? There are usually three main ones for different focusing range.

The lens looks like this:

https://www.ebay.com/itm/RT-JML-OPTICAL-35MM-F-1-4-611-/401738784077

Thanks a lot for any information.

1. Don't know – probably non-trivial.
2. C-Mount lenses are designed with image circles much smaller than full frame.
3. Sorry, that won't work.

There are adapters from C-Mount to Sony E-Mount, but these need to recess the lens 0.5mm inside the camera's throat to allow focusing to infinity. This doesn't allow any room for a helicoid or extra adapters, and also means that some lenses with flush rear mounts may not fit. There's lots more information on all of this here:

https://www.instructables.com/id/C-Mount-Lenses-for-mirrorless-micro-43-and-APS-C/

Hope this helps.


PostPosted: Wed May 08, 2019 4:34 pm    Post subject: Reply with quote
Thanks. I am aware of the C to Nex adapter but I need something to focus. Most likely I will give up on this one due to the small effective image area on the full frame.


PostPosted: Thu May 09, 2019 1:19 am    Post subject: Reply with quote
vivaldibow wrote:
Thanks. I am aware of the C to Nex adapter but I need something to focus. Most likely I will give up on this one due to the small effective image area on the full frame.

It's hard to say for certain what size the image circle will be, The Fujian 35/1.7 has a bigger image circle than the C mount format, it's image circle covers APS-C.

The first thing I'd do is free-lens the lens to see how big it's image circle is.

You may be able to remove the mount and possibly more to gain some register distance, there is a ring near the cable that has screws, is this part of the mount? (A spacer ring?) or does it hold the rear elements? Is it to access the aperture system?
Lots of questions....
This lens may be interesting to M4/3 shooters(assuming it doesn't cover APS-C) if you can get some room for a helicoid.

You could also contact https://www.jmloptical.com/ to find out what the specs are, I would talk to them before doing anything.


PostPosted: Thu May 09, 2019 12:55 pm    Post subject: Re: JML 35mm f/1.4 with electronic shutter Reply with quote
vivaldibow wrote:
1. Is it easy to disassemble the lens to disengage the electronic shutter?

I haven't used this specific lens, but most similar C mount lenses have just a remotely controlled aperture, no shutter. I have dismantled a few of those and often there is a small motor turning a cog to open/close the aperture. That cog or a lever attached to it may also be used to open/close it manually, probably not in a very convenient way though.

vivaldibow wrote:
2. As it is a C mount lens, how much will it cover the full frame? I guess it will have an image circle.

I have not encountered any C mount lens of 35mm focal length that covers full frame. The C mount physically blocks the image even if the lens may project a larger one. Even with the C mount removed, I think 70mm was the shortest focal length that just about covered full frame, or maybe 100mm.

vivaldibow wrote:
3. I plan to have a C-M42 adapter, M42 to Nex focusing helicoid. What kind of helicoid should I use? There are usually three main ones for different focusing range.

As mentioned before, that won't work, at least not when you want infinity focus. But maybe you don't need an extra helicoid for focussing, my guess is the lens does have one, it just isn't marked as such. Try turning the rear ring on the lens.


PostPosted: Fri May 17, 2019 5:53 pm    Post subject: Reply with quote
I would shy away from this. First, you will probably have an image circle no larger than 20mm or so. Second, without a focusing mechanism, you are dead in the water. Fitting any kind of helicoid is going to bring you into macro territory at minimum focusing distance, and the third strike is lack of manual diaphragm control. NB--I just noticed that you are planning to use C mount to M42 to NEX. Impossible. You would need C mount to NEX, which is already recessed ~1mm into the body.


PostPosted: Fri May 17, 2019 8:28 pm    Post subject: Reply with quote
kymarto wrote:
I would shy away from this. First, you will probably have an image circle no larger than 20mm or so. Second, without a focusing mechanism, you are dead in the water. Fitting any kind of helicoid is going to bring you into macro territory at minimum focusing distance, and the third strike is lack of manual diaphragm control. NB--I just noticed that you are planning to use C mount to M42 to NEX. Impossible. You would need C mount to NEX, which is already recessed ~1mm into the body.


Thanks everyone. I already returned the lens with the loss. My C to M42 is on its way anyways. Will need to find an longer focal length C mount lens.


PostPosted: Sat May 18, 2019 12:02 pm    Post subject: Reply with quote
vivaldibow wrote:
kymarto wrote:
I would shy away from this. First, you will probably have an image circle no larger than 20mm or so. Second, without a focusing mechanism, you are dead in the water. Fitting any kind of helicoid is going to bring you into macro territory at minimum focusing distance, and the third strike is lack of manual diaphragm control. NB--I just noticed that you are planning to use C mount to M42 to NEX. Impossible. You would need C mount to NEX, which is already recessed ~1mm into the body.


Thanks everyone. I already returned the lens with the loss. My C to M42 is on its way anyways. Will need to find an longer focal length C mount lens.


Are you using a full frame camera? No C mount lens I know of fills that sensor, the mount itself causes vignetting.


PostPosted: Sat May 18, 2019 10:18 pm    Post subject: Reply with quote
vivaldibow wrote:
kymarto wrote:
I would shy away from this. First, you will probably have an image circle no larger than 20mm or so. Second, without a focusing mechanism, you are dead in the water. Fitting any kind of helicoid is going to bring you into macro territory at minimum focusing distance, and the third strike is lack of manual diaphragm control. NB--I just noticed that you are planning to use C mount to M42 to NEX. Impossible. You would need C mount to NEX, which is already recessed ~1mm into the body.


Thanks everyone. I already returned the lens with the loss. My C to M42 is on its way anyways. Will need to find an longer focal length C mount lens.


I have a number of long focal length lenses in C mount. In every case the mount causes vignetting at longer focal distances even on APS-C sensors. I have removed the C mount in most cases and re-adapted them, but you cannot do that with all longer focal length lenses, especially faster ones, which tend to have small image circles in order to achieve the lower f stop.


PostPosted: Sat May 18, 2019 11:28 pm    Post subject: Reply with quote
kymarto wrote:
vivaldibow wrote:
kymarto wrote:
I would shy away from this. First, you will probably have an image circle no larger than 20mm or so. Second, without a focusing mechanism, you are dead in the water. Fitting any kind of helicoid is going to bring you into macro territory at minimum focusing distance, and the third strike is lack of manual diaphragm control. NB--I just noticed that you are planning to use C mount to M42 to NEX. Impossible. You would need C mount to NEX, which is already recessed ~1mm into the body.


Thanks everyone. I already returned the lens with the loss. My C to M42 is on its way anyways. Will need to find an longer focal length C mount lens.


I have a number of long focal length lenses in C mount. In every case the mount causes vignetting at longer focal distances even on APS-C sensors. I have removed the C mount in most cases and re-adapted them, but you cannot do that with all longer focal length lenses, especially faster ones, which tend to have small image circles in order to achieve the lower f stop.


Thanks. I've seen photos taken with c mount lenses with long photo length without vignetting. I guess those pictures were probably cropped.
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