Advice from Optitek ProLock owners needed while Jacek is on holiday

[Petri Teittinen]

Please drop me a PM if you have a Optitek Prolock Nikon mount and you're familiar with it. Thank you.

 

[Petri Teittinen]

Problem solved! Thank you everyone who helped!

 

[Petri Teittinen]

Could ProLock owners please take a look at their camera and let me know how much of a gap (see image below) there is between the camera body and the backfocus ring when you've set the backfocus with a Nikon lens?

 

[Peter Matthes]

Petri,

I do not own a Nikon mount for my Red One, and I do not have the Optimator.

However, I have been reading your posts. You seem to be finding that you really have to turn the living hell out of your backfocus ring just to bring your Nikon lenses into proper focal alignment. Is the gap on your camera making you feel something is not right?

 

[Petri Teittinen]

You seem to be finding that you really have to turn the living hell out of your backfocus ring just to bring your Nikon lenses into proper focal alignment. Is the gap on your camera making you feel something is not right?

Thank you for posting Peter, much appreciated!

Yeah, I'm having some problems with backfocus. I tried setting it with a pretty good Nikon 24-70 zoom lens, and I'm running out of backfocus adjustment room. I focused the long end of the zoom first using lens focus, then tried to set wide end with camera's backfocus ring.

It's not far off - though obviously unfocused - and to get it really focused I would need to turn the backfocus ring a bit more counter-clockwise (standing behind the camera), i.e. closing the gap between the camera body and the backfocus ring, and bringing the lens closer to the sensor.

But the backfocus ring is already at the end of its run and the lens is as close to the sensor as I can get it.

If I turn the BF ring clockwise, moving the lens away from the sensor and opening a tiny gap between the BF ring and camera body, the image on my LCD goes even more unfocused immediately.

I really don't know what to do about this.

cheers,
.: petri

 

[chuck colburn]

This may be stupid of me to ask, but is the footage scale on the lens set to appx. the distance that the camera is from what ever your target is? Such as outdoors at infinity or the footage from a target inside.

 

[Peter Matthes]

IMHO ... you don't want to be using a zoom lens to set your backfocus. Use a prime lens.

P.S. You have inadvertently let everyone know that you own "Con Air" and "Face Off" on DVD. :001_smile:

 

[Nick Gardner]

P.S. You have inadvertently let everyone know that you own "Con Air" and "Face Off" on DVD.

Yeah, that kind of humiliation is hard to come back from.

 

[Petri Teittinen]

This may be stupid of me to ask, but is the footage scale on the lens set to appx. the distance that the camera is from what ever your target is? Such as outdoors at infinity or the footage from a target inside.

Hi Chuck, thanks for posting. It's not stupid at all, considering that I'm pretty much a complete beginner and very likely to do stupid things

The only way I can get the distances to ~match is to tighten the backfocus ring as far as it goes. I haven't tried infinity outdoors yet, but I plan to try that this weekend.

 

[Petri Teittinen]

IMHO ... you don't want to be using a zoom lens to set your backfocus. Use a prime lens.

Hmm. There seems to be two schools of thought when it comes to that. I will try a prime lens (again) this weekend.

P.S. You have inadvertently let everyone know that you own "Con Air" and "Face Off" on DVD. :001_smile:

Oh, the shame, the shame! What can I say... except that they're both Blu-rays and I got them for free for review purposes. I won't say no to free s***, you know!

 

[Petri Teittinen]

Yeah, that kind of humiliation is hard to come back from.

I'd better not go into what else I have in my Blu-ray shelf...

 

[chuck colburn]

Petri,

I take that your len(s) work ok on a still camera body. Since you are using a zoom lens set your camera about five feet from what ever your target is. If you don't have a resolution target download a siemens star target from wikipiedia or where ever and hang it on the wall. Now set your lens on telephoto and the footage scale at whatever the measured distance is from the target to the film (sensor) plane. Try getting the focus adjuster to give your an infocus image. If you can do this now zoom to the wide end of the zoom and repeat the focus adjustment. Now zoome to the tele end again and check the focus. If you need to readjust it a bit do that and zoom back to the wide end again and check focus there. If this does not work then something is either wrong with your lens or the focus adjuster on the camera body.

http://www.google.com/imgres?imgurl...mage_result&resnum=1&ct=image&ved=0CAkQ9QEwAA

 

[Petri Teittinen]

I take that your len(s) work ok on a still camera body.

Absolutely. No problems at all on my D3.

Since you are using a zoom lens set your camera about five feet from what ever your target is... (snip) If this does not work then something is either wrong with your lens or the focus adjuster on the camera body.

That sounds very close to what I tried, actually. Like I mentioned, the backfocus ring runs out of adjustment room when trying to focus wide end. As the lens is fine, I guess there's something wrong with camera backfocus adjuster.

Now that you mentioned this, I remember I loosened the two screws on the BF adjuster so much at one point that the ring felt really loose. Could it have jumped a few grooves then, making it run out of adjustment room sooner than it should?

 

[Nick Gardner]

It should be pointed out that still lenses are not great at holding focus throughout their zoom range, so trying to set backfocus with a still zoom in this manner may be chasing ones tail.

Nick

 

[Petri Teittinen]

That's a good point, Nick. Thank you. I think I'll give up on trying to use a zoom lens for this. Back when I tried to set bf for the first time, I used a very cheap 50mm Nikon prime and got some rather negative feedback (totally deserved, I'm sure) for that in another thread. Unfortunately my best prime is a 105mm one... although that could come handy when setting backfocus outdoors at infinity, right?

 

[Peter Matthes]

It should be pointed out that still lenses are not great at holding focus throughout their zoom range, so trying to set backfocus with a still zoom in this manner may be chasing ones tail.

Nick

That was my point exactly. Nick is spot on. Still zoom lenses often have trouble holding their focus throughout the zoom range. They are principally manufactured to find a frame ... focus ... and take the picture.

Try setting the backfocus with a trusted prime lens.

BTW ... Petri ... Just pulling your leg about your Nick Cage collection. :001_tt2:

 

[Petri Teittinen]

That was my point exactly. Nick is spot on. Still zoom lenses often have trouble holding their focus throughout the zoom range. They are principally manufactured to find a frame ... focus ... and take the picture. Try setting the backfocus with a trusted prime lens.

Will do. I think the 105mm one cost something like $2000 back in 2008. I'll lug the camera outside tomorrow and try to set BF at infinity. There's a nice garden shed approx. 150 feet away across the road, that'll do nicely I believe. But what if the BF ring runs out of adjustment room again?

BTW ... Petri ... Just pulling your leg about your Nick Cage collection. :001_tt2:

D'oh! I didn't realize he was in both movies until now. At least I don't own Ghost Rider...

 

[chuck colburn]

Absolutely. No problems at all on my D3.


That sounds very close to what I tried, actually. Like I mentioned, the backfocus ring runs out of adjustment room when trying to focus wide end. As the lens is fine, I guess there's something wrong with camera backfocus adjuster.

Now that you mentioned this, I remember I loosened the two screws on the BF adjuster so much at one point that the ring felt really loose. Could it have jumped a few grooves then, making it run out of adjustment room sooner than it should?

Hi Petri,

I assume that the thread in the focus adjuster is of a fine pitch and a single start so it is not likley that the male and female pieces seperated from each other no matter how loose the lockdown screws got. Perhaps Brent or the optical/mechanical tech. at RED could answer that question. That 105mm should be good for backfocus adjutment to to it's realetive shallow depth of field. A brick wall around 100' away should do it.

One other thing, does the Nikon mount come with shims that mount behind it on the focus adjuster? If so are they in there?

 

[Jacek Zakowicz]

Prolock setup

Prolock setup

No shims Chuck-the mount thickness compensates the BF difference precisely. Sometimes small adjustment is needed but nowhere near what we are seeing. I suspect that Petri could have disengaged the threads and needs to bring it back. If someone in Sweden near him could get him a wide angle PL lens so he can just put the original PL on, focus and swap mounts for PL that I think would be the easiest. Otherwise you need a "hero" Nikon lens.
Here is the video that shows the installation.:gnorsi:
http://www.youtube.com/watch?v=AeEOnklv7Z8

 

[chuck colburn]

No shims Chuck-the mount thickness compensates the BF difference precisely. Sometimes small adjustment is needed but nowhere near what we are seeing. I suspect that Petri could have disengaged the threads and needs to bring it back. If someone in Sweden near him could get him a wide angle PL lens so he can just put the original PL on, focus and swap mounts for PL that I think would be the easiest. Otherwise you need a "hero" Nikon lens.
Here is the video that shows the installation.:gnorsi:
http://www.youtube.com/watch?v=AeEOnklv7Z8

Yeah a wide angle would be good due to it's inherent shall depth of "FIELD" not to be confused with depth of focus.