Infinity focus with SLR Magic lens?

Hi everyone,

I bought a lens on eBay that looks identical to the SLR Magic 35mm f/1.7 lens. It came with a C-mount to NEX adapter.

I can't focus to infinity and was wondering if I got a bad adapter (too thick).

What is everyone's experience with infinity focus on the SLR Magic (or any C-mount lens for that matter)?

--Xavier

Anyone?

xbourque said:

Hi everyone,

I bought a lens on eBay that looks identical to the SLR Magic 35mm f/1.7 lens. It came with a C-mount to NEX adapter.

I can't focus to infinity and was wondering if I got a bad adapter (too thick).

Click to expand...

There are two C-mount standards, one (CS) being 5mm shorter register than the other. (see http://en.wikipedia.org/wiki/C_mount for details). It sounds like your adapter is CS rather than C.

xbourque said:

What is everyone's experience with infinity focus on the SLR Magic (or any C-mount lens for that matter)?

Click to expand...

My Fujian TV lens focuses way past infinity on a C adapter, so far past infinity that I assumed it was really a CS lens. I bought a cheap CS-C adapter (it's just a 5mm extension tube) to try and found it would then only focus to a few feet away, much like yours. So in the end I removed the CS adapter and used a couple of washers to get better close focus with the standard C adapter. I have no idea why the lens doesn't seem to match the index of either C or CS, falling somewhere between the two, but that's the inscrutable Chinese for you.

Anyway, bottom line is you almost certainly have a CS adapter when you should have been supplied with a C adapter. It's possible the seller doesn't even know the difference.

PS: The SLR Magic has an integrated custom-made mount that replaces the C mount, it doesn't use an adapter at all so the same considerations don't apply.

--
John Bean [GMT]

Couldn't edit my post :-(

What I meant to say was I thought my adapter was CS rather than C, and that the lens was standard C.

The "bottom line" comment is therefore exactly back to front: I should have said you probably need a CS (5mm thinner ) adapter rather than C to allow infinity focus.

Sorry about that, I posted before I had my first coffee of the day.

--
John Bean [GMT]

Thanks for the info. A quick eBay search reveals no hits for a CS-mount to NEX adapter.

A heads up for future buyers, even though the photo on the auction page I bought from showed a "Fujia GDS-35" (note: not Fujian) I received a WSL-35 with no brand markings anywhere.

I got what appears like 2 C to CS adapters in the box... so now I'm really confused. That would imply the lens is "C" and that the adapters are there for the lens to be mounted on CS cameras.

Anyways, thanks for the feedback. I just wanted to know if anybody got these cheap CCTV lenses to focus at (or past) infinity before I sunk more money down that hole.

Otherwise that lens is great fun to shoot with, and the fact that it's light, tiny and cheap is awesome too. ;-)

-Xavier

I have regular DSLR magic with the mount gor NEX, no problem with infinity focusing...

https://picasaweb.google.com/novakrogic/Barcelona?authkey=Gv1sRgCJ3br5un4-XlTw#slideshow/5535760756756768914

--
http://www.supernovak.com
http://www.flickr.com/photos/rogic

FED-S (my father's) > Canon AE1 (my brother's) > Minolta Maxxum 3xi (my first precious) > Minolta Dynax 400si (hello Canada) > Minolta Dimage 7i (darling) > Konica Minolta 5D (first DSLR) > Sony Alpha A100 (killer baby) > Sony Alpha A700 (serious tool) > Canon 5DMkII (weird computer with average lenses) > Back to A700 (reassured about the greatness) + A900 (depth of colours and pixels)

Playing a little bit more with my lens, I was able to unscrew and remove the mount on the lens. I was able to focus way past infinity just by holding the lens against the C-Mount to NEX adapter.

I'm tempted to ditch the mount and just glue the lens to the C-mount/NEX adapter.

-X

(In case anyone is wondering, I didn't get the SLR Magic kit because they don't deliver to Canada)

that's weird, they shipped to me (in Vancouver), no prob
--
http://www.supernovak.com
http://www.flickr.com/photos/rogic

FED-S (my father's) > Canon AE1 (my brother's) > Minolta Maxxum 3xi (my first precious) > Minolta Dynax 400si (hello Canada) > Minolta Dimage 7i (darling) > Konica Minolta 5D (first DSLR) > Sony Alpha A100 (killer baby) > Sony Alpha A700 (serious tool) > Canon 5DMkII (weird computer with average lenses) > Back to A700 (reassured about the greatness) + A900 (depth of colours and pixels)

xbourque said:

Thanks for the info. A quick eBay search reveals no hits for a CS-mount to NEX adapter.

Click to expand...

I think my initial (wrong!) reply caused confusion; you probably already have a CS adapter - that's why it wont focus to infinity. With a normal C adapter it focuses past infinity. Ebay sellers don't seem to know the difference.

xbourque said:

I got what appears like 2 C to CS adapters in the box... so now I'm really confused. That would imply the lens is "C" and that the adapters are there for the lens to be mounted on CS cameras.

Click to expand...

No, that's the wrong way around. The adapter is to allow a CS lens to mount on a C camera, you can't mount a CS lens on a C camera and get infinity focus. Don't know why you got two though; are they different lengths?

--
John Bean [GMT]

xbourque said:

I'm tempted to ditch the mount and just glue the lens to the C-mount/NEX adapter.

Click to expand...

Sounds reasonable, if you don't need close focusing. If you experiment with a few spacers - maybe one of the CS adapters filed down? - you can probably make it focus perfectly.

--
John Bean [GMT]

they do ship to Canada! I recommended my friend to buy one off them and he managed to buy one with CAD. I think you need to contact them about shipping to certain countries.

xbourque said:

Playing a little bit more with my lens, I was able to unscrew and remove the mount on the lens. I was able to focus way past infinity just by holding the lens against the C-Mount to NEX adapter.

I'm tempted to ditch the mount and just glue the lens to the C-mount/NEX adapter.

-X

(In case anyone is wondering, I didn't get the SLR Magic kit because they don't deliver to Canada)

Click to expand...