Calibrating 7Artisans / TTArtisan Lenses on a Film Body

[pk851667]

Hey all,

I've played around with these lenses before and I suppose I've had good luck with them in terms of calibration.

I just bought a 50mm 1.4 from new but this one seems to be a fair bit off. I've tried to calibrate it by switching back and forth from my mirrorless to M5 to get it calibrated but I still unsure if it's correct.

Does anyone have any better ways to do this on film body other than wasting a ton of film?

 

[Rayt]

Do you have a piece of ground glass you can use on the film plane?

 

[pk851667]

I have a 35mm focusing screen from an F1 or something lying around. I was thinking of using that, but I don't know whether or not those are magnified at all.

Otherwise, I've tried the frosted tap method, but I couldn't see anything and deemed it pointless.

Don't even know where I can get a peace of ground glass at that size.

 

[hipsterdufus]

You can also tape a piece of Scotch tape along the film plane and then use a loupe for magnification. But I think you're probably sending it off to a tech for calibration, especially with super-thin DOF. Minute differences will be hard to detect with my ghetto method.

 

[Ko.Fe.]

I had my J3 calibrated for M back then I had no digital M. It is spot on @f1.5. Close and infinity.

You could use anything which has frosted surface on one side. CD covers, plastic boxes.
Main thing is to have in on film channel flat.

Calibration is done at minimal distance or one meter.
Wait for dark. Have focusing target as black cross on white.
Camera on tripod, focus target is lit by spot light. Everywhere else should be dark.
Use anything available to magnify the view. Lope, camera with macro lens, phone camera.

Try to use infinity method. Might works as well.

http://elekm.net/zeiss-ikon/repair/collimate/

 

[mpaniagua]

I used an old focusing screen from a broken Pentax. I my Bessa T because it was easier than my other 2 M mounts (M5 and M6). I tried with a piece of wax paper but didnt work. Used a luminous lens, probably an F2 or Canon 1.8, not sure. Mount on a tripod focusing an static object (I think it was a lamp). First focused with camera rangefinder and then check that image on focusing screen was right. Otherwise, unmount lens, adjust and try again . Didnt waste a single frame of film and my lens is ok now.

 

[kram]

Tracing paper or grease proof paper works OK.

 

[pk851667]

Update for everyone - I used a focusing screen from an SLR and it worked perfectly. Thanks for the help.

Now is there any way to adjust the infinity hard stop? The lens still focuses past infinity at the hard stop.

 

[Phil_F_NM]

Use a piece of film with fine crosshatch XXXXXX marks across it.
Tape that to the film plane and ensure it is flat using something like a piece of translucent plexi or glass.
Mount the lens.
Set the aperture to its widest setting.
Set the lens to infinity.
Mount the camera to a tripod or level and steady on a table.
Shine a light at the back of the RF camera to ensure the film is illuminated from behind.
Get the SLR of your choice with a relatively fast and long focal length lens mounted.
This SLR lens should be a known good sample that focuses accurately at infinity.
Set the SLR lens wide open and to infinity.
Move the SLR lens as close as possible to the RF lens to be calibrated, ensuring the two lenses are aligned on the same axis.
Look in the SLR to check the focus of the film in the RF. You should be able to see great detail in the XXXXXs you drew on the film.
If the film is not in focus, adjust the RF lens and recheck.
Wash, rinse, repeat, until it's right.
Looking at a groundglass on the film rails may not take into account the thickness of the film if the GG is too large and it's simply not as accurate as the above method.
(I give credit to Sam AKA Crazy Fedya here on the forum for this great method.)

Phil Forrest

 

[pk851667]

Hey Phil,

I'm having a tough time imagining this.

The question I'm asking is how do you physically adjust this on the lens? This lens already accurately focuses to infinity on my rangefinder. Therefore, calibration isn't needed. I just need to move the hard stop over a few degrees as the hard stop is past infinity.

 

[pk851667]

These lenses don’t come calibrated. It’s a corner they cut to keep costs down and a means to tune it perfectly to your own camera.

Still this doesn’t help me much on shifting the infinity hard stop.

 

[Godfrey]

These lenses don’t come calibrated. It’s a corner they cut to keep costs down and a means to tune it perfectly to your own camera.

Still this doesn’t help me much on shifting the infinity hard stop.

To adjust the infinity hard stop would usually involve adding material to the focusing helicoid in order to engage the stop limit in the mount at the correct point, or shifting the distance scale on the focusing helicoid. Not knowing the lens's construction, I don't know how you'd do this.

My quick'n'dirty approach would be to simply mark the correct infinity registration. Then you focus with the rangefinder, look at the offset between the marked infinity stop and the proper infinity position, and move the focusing helicoid that amount. It should be a constant throughout the focusing range.

G

 

[Sarcophilus Harrisii]

These lenses don’t come calibrated. It’s a corner they cut to keep costs down and a means to tune it perfectly to your own camera.

Still this doesn’t help me much on shifting the infinity hard stop.

Okay. Sounds like you're getting your moneys worth, then.

 

[pk851667]

To adjust the infinity hard stop would usually involve adding material to the focusing helicoid in order to engage the stop limit in the mount at the correct point, or shifting the distance scale on the focusing helicoid. Not knowing the lens's construction, I don't know how you'd do this.

My quick'n'dirty approach would be to simply mark the correct infinity registration. Then you focus with the rangefinder, look at the offset between the marked infinity stop and the proper infinity position, and move the focusing helicoid that amount. It should be a constant throughout the focusing range.

G

Thanks for this.

Would that simply entail undoing the screws on it and shifting it over while loose?

 

[Ko.Fe.]

These lenses don’t come calibrated. It’s a corner they cut to keep costs down and a means to tune it perfectly to your own camera.

Still this doesn’t help me much on shifting the infinity hard stop.

Usually lens focusing helicoid and focus scale ring are kind of interconnected. I mean, they are made to align in one combination of multi-entry helicoid two or three tubes and external focus scale ring.