Cambo SK 35mm lens adjustment

[Guy Mancuso]

Okay I am coming up short of focus on the infinity mark on my SK 35mm been looking around to see how I can adjust the lens past the infinity mark and see nothing out there. Any help or guidance would be useful.

[etrump]

Guy, thomas made a great post on this when I was having trouble with my 72L but I cannot find it. You may have better luck than I did trying to search with cr8ppy hotel internet.

Basically what I do is:

1. Tether
2. Set the lens wide open
3. Loosen the three screws on the focus ring.
4. Force infinity to be front focus by holding the back ring and turning the front (or vise versa)
5. Start taking tethered shots viewed at 100% in C1
6. Move the focus towards infinity until the furthest items pop into focus.
7. Tweak until you are sure you have it as sharp as possible but don't move any further back than you have to cuz it messes up the hyper focal scale worse than it already is. Once I get it as sharp as I can I move it back forward so I am right on the edge of infinity.
8. Move the focus dial to line up infinity then tighten the screws
9. Test to make sure something didn't slip and if something isn't right start over.

It's pretty easy, takes about 30 minute on the first lens and 10 minutes on subsequent lens. I do it on all my glass after anything changes or I upgrade the back.

Whatever you do, don't mess with the rear standard adjustment screws unless you are comfortable calibrating the whole camera. I ended up sending my back to cambo to ease my mind that I hadn't hosed it by turning a few of those screw in screw monsters. While you're at it; if your back slips in the adapter plate at all you can remove the bottom hook and remove a couple of the shims until it sits tight. Rene' at cambo told me the tolerances for some of the backs were changed at one point (P65 i think) but have since been changed back.

I have a spot on the sidewalk in front of my office that allows me to see a mcdonalds sign and some cell towers I know are more than 2 miles from where I am. You don't need that much space but it helps when there are a lot of different objects to check sharpness.

Thomas, if you read this I would appreciate any corrections.

[Guy Mancuso]

Thanks Ed was thinking of looking for that also. I remember someone giving exact directions on this and also calibrating the plate on the body but reluctant to do that.

[thomas]

here's the initial post:
http://forum.getdpi.com/forum/showpo...postcount=4572

[jlm]

i also bumped this cambo tips and tricks on lula

http://www.luminous-landscape.com/fo...topic=49977.20

[Guy Mancuso]

You guys rock. Thanks will get working on this immediately

[Guy Mancuso]

WOW major improvement on my 35mm lens. It turns out i had to back off infinity. No wonder i was getting some great and some okay sharpness sometimes i don't always go to infinity. I say 2mm backed off from existing infinity mark. It is sharp as a tack wide open now. Moving on to others. I think my issue came about when I went from RS and its plate to AE model and new plate which Bob adjusted for me to be tighter on the mount and I never tested this AE setup. Freaking awesome

Now I will test the 60 and 90 to be sure they are okay. I am tethered BTW which helps a lot so does focus mask as i can see it as well.

[Guy Mancuso]

60 and 90mm are dead on the money wide open. Just my 35mm was out there in La La land. Thanks

[danlindberg]

I had my SK 35 recalibrated by Schneider in Germany. WOW the difference! Stellar!

[Guy Mancuso]

It was actually pretty easy . One trick I figured out was don't take the screws out all the way but the front ring could still move. This way as soon as you get it you can at least set one screw to lock it down until you lock the rest down without moving. First time I did not do it this way and it moved and had to go back and do it again. Lesson learned

[Guy Mancuso]

So I had a forum member here for a one on one workshop for 3 days come into town and I adjusted his XL 35mm lens which is brand new and same situation. Infinity mark past infinity focus. So adjusted his as well. Major difference

[etrump]

Originally Posted by Guy Mancuso

WOW major improvement on my 35mm lens. It turns out i had to back off infinity. No wonder i was getting some great and some okay sharpness sometimes i don't always go to infinity. I say 2mm backed off from existing infinity mark. It is sharp as a tack wide open now. Moving on to others. I think my issue came about when I went from RS and its plate to AE model and new plate which Bob adjusted for me to be tighter on the mount and I never tested this AE setup. Freaking awesome

Now I will test the 60 and 90 to be sure they are okay. I am tethered BTW which helps a lot so does focus mask as i can see it as well.

I had the same issue with my hr32 and 72l. When you get it calibrated, the difference is pretty amazing. I rarely have focus problems now but for a while it was pretty frustrating.

[jlm]

got me motivated. found the 43 and 70 were at infinity focus a bit before the stop (about 1/8" -3/16"on the barrell) implying the back needed to be a bit farther away.

with the cambo, you can move the back by removing the four screws at each corner and screwing in the bushings a bit. took three attempts, sneaking up on it, altogether about 90 degrees rotation per bushing (see the cambo tips link)

then put on the 120 and found it was not moving quite far enough to reach focus at inf, so used the info in the first link to adjust the inf stop on the lens.

did this tethered, IQ 160, image size 100%; hardest part was finding the perfect target. distant tree limbs against the sky were not so good, same for a distant antenna. ended up using a fire escape against a not-so contrasty background.

[Guy Mancuso]

I think that is the theme John these lenses are a bit short of the stop mark at infinity. Personally I want to hit the stop mark knowing it is dead on infinity and not beyond. Now my 60mm is deadly at the stop the 90mm I am going to try again with a subject further out. I'm getting pretty nit picky on this one.

[cng]

I've noticed that infinity on my SK35, 43 and 150 are all off by a consistent amount. Haven't conclusively tested my SK60 yet, but I am guessing the same result.

Regardless of lens, infinity is consistently EXACTLY MIDWAY between the infinity mark and the next marked distance on the focusing ring. Any more or less and the image starts to go soft.

Given my observations and everyone else's experiences with this, it seems to be done on purpose by Schneider. This margin of error is much too large to be explained by the need to account for thermal expansion/contraction.

No complaints about the lenses, just wondering if anyone has found the same as me and/or any ideas as to why Schneider is doing this?

[Guy Mancuso]

It's a great question and I agree the expansion/contraction amount of play should be much less than what I found. Funny thing is my new 60XL seems to be dead on the money. I adjusted my 35 and 90 now

[Guy Mancuso]

We are in Death Valley right now and we have just about every lens made in Cambo mount from the folks at Capture Integration so like to see how this plays out this week as we will be working with them all with our attendees. Lots of infinity around here. LOL

[jlm]

how is that moon?

[cng]

Thanks Guy. The thing that gets me is the consistency with which each of my lenses is "off": actual infinity on three Cambo/SK lenses being exactly midway between infinity and the next marked distance, and all three lenses are of different focal lengths ranging from short to long – that's pretty weird. And they were all bought at different times, so not part of a single order/shipment – even weirder.

I'm not the biggest lens tester in the world and my lenses all seem OK performance-wise, but Live View on my IQ confirms what I am seeing with regards to focusing. I'll be interested to hear any explanations/theories.

[Guy Mancuso]

Originally Posted by jlm

how is that moon?

Waiting for YOU. Lol

Heading out to scout more now