SALT II results... (Part 1,2,3,4 Bokeh, Breathing & Flare and Part 5: Impressions)

[Martin Stevens]

Setting the backfocus on a lens needs to be done at an optical facility or a camera house with a lens collimator.

I understand that this might be the BEST way to do it, but I assume that it is not the only way.

[Martin Stevens]

Martin, use the widest, fatest lens you have and set the sensor plane on a tripod at a marked distance from a focus chart. Use the 1:1 mode and either the focus or outline modes to help you determine if the image is sharp at the marked distance (6 feet is a good staring place). If your three widest lenses tape out correct you're probably good. If you have a zoom you'll notice that the focus will not hold through the range if the backfocus is out. Unless of course it's a still lens and then it just may not be parfocal.

THANKS EVIN

[Jacek Zakowicz]

It's important to mention that you have to be absolutely sure that your lens marks are correct. otherwise you are setting incorrect base line for your system and all bets are off...

[Evin Grant]

I will say that yes, you need to use a lens you know is calibrated correctly to check the body backfocus and I would not use still lenses for this. The Optitek Optimator is also very useful if you change mounts often. It is certainly possible to do yourself but only if you have the knowledge and understanding of the limitations. Since I have my lenses checked out every 6 months or so I feel confident using them to check the camera. However the Titanium PL mount of the Epic is very solid and I have yet to even need to adjust mine.

[Phil Holland]

Heh heh. Thanks for adjusting my backfocus with the Optitek Optimator Evin. Appreciate it!

[Mitch Gross]

I understand that this might be the BEST way to do it, but I assume that it is not the only way.

No, it's the only way. Certainly one can work his or her way to a somewhat correct backfocus on the camera using a properly set lens. But there is no way to collimate a lens itself without the correct tools. A collimator costs many tens of thousands of dollars and the precision shims used to set the mount are measured in microns.

[Joshua Brown]

No, it's the only way. Certainly one can work his or her way to a somewhat correct backfocus on the camera using a properly set lens. But there is no way to collimate a lens itself without the correct tools. A collimator costs many tens of thousands of dollars and the precision shims used to set the mount are measured in microns.

What he said. But really it's a rather precise process filled with lots of trial and error based off years of experience for professionals. I've got a lot of respect for anyone who can correctly set back focus for their own lenses.

[Tom Hamilton]

Really like my Duclos Cine-mods ZFs and his 11-16mm here!

Have just acquired a Nikon 14-24, give it a go, you won't be sorry.

[Evin Grant]

I'm sot saying it's a good idea, but myself and many a 1st AC has had to make a "Field adjustment" to a lens that just wasn't holding focus. Certain lenses like older Cooke zooms are easier than others, I woukdn't crackopen a Master prime or Leica Summilux-c which I hear can only be calibrated with a laser (can anyone confirm this?).

[Martin Stevens]

No, it's the only way. Certainly one can work his or her way to a somewhat correct backfocus on the camera using a properly set lens. But there is no way to collimate a lens itself without the correct tools. A collimator costs many tens of thousands of dollars and the precision shims used to set the mount are measured in microns.

Okay, but then what is the Red Focus product from Red for?
It does not cost many tens of thousands of dollars.

Perhaps collimating a lens is different than collimating a camera sensor/or moving the camera sensor.....if that makes any sense.

What I was really trying to ask earlier was if your backfocus if off a bit can you still get sharp imagery
with your lens even though the lens distance marking will not match the real world distance?

Or in other words, if your lens had NO markings on it, could you still get a sharp image even if the
backfocus was off a bit?