S&K 43XL Arca-Swiss Rm3d/i Focus Chart - PDF

[JRBERNSTEIN]

I decided to create a PDF for my phone of the little focus chart that came with the R-mounted 43XL, and thought I'd share.

As I was transcribing the numbers, I noticed there were actually a couple mistakes on the original card, so I've fixed those too.

Let me know if you find any issues, or would like to see any changes.

Enjoy!
J R

 

[Frederic]

Thanks for sharing this. I've made a .txt version for the Rod 40 HR too, will post it here too when back home.

You say you noticed and fixed errors, does that mean you know the formula used ?

 

[gazwas]

You say you noticed and fixed errors, does that mean you know the formula used ?

+1

How do you know there are errors - have you tested?

Only problem is each camera/lens combo will have a slightly different chart because of the focus offset adjustment/calibration.

 

[RodK]

The focus cards were recently replaced as more information was gleaned from Rodenstock and Schneider. They should be now quite accurate especially from 20 times the focal length for standard to wides angles to 25 times for longer lenses. Inside of these distances a user should do testing to determine the correction as the lenses change 'character', and this is a problem. The precision of the R cameras has shown this error even though it was always present. At these distances, a ground glass can be helpful at determining the correct setting for your lens/back combination.
By the way, I have just received most of the latest focus cards and can send them out to anyone who emails me.
Hope this helps.
Rod

 

[Frederic]

Here's the one I got with the Rodenstock HR40, I assume it's the recent version.

 

[JRBERNSTEIN]

Regarding the errors on the original chart: No, sadly I don't have the formula that's being used, but that said, the errors were quite obvious. For one, my chart has 4.6m and 4.8m as the SAME focus mark, 6.1. That can't be correct. Second, 2.4m is listed as 17.7, but 2.2 is 12.8 and 2.6 is 10.8! Also, clearly incorrect.

So what I did was to graph out all the values, remove the offending points (which I could see a couple more minor ones with everything all graphed out), and smooth the curve. Once I had a smooth curve, I read the missing points. Pretty simple really.

 

[JRBERNSTEIN]

+1

How do you know there are errors - have you tested?

Only problem is each camera/lens combo will have a slightly different chart because of the focus offset adjustment/calibration.

Yes, you're right, each camera/lens combo *should* have their own chart with the offset factored in. And you can do that yourself if you want to bother.

This chart has a 0-offset. So just factor your offset in. Mine is +1.6, so I just add 1.6 to any number I'm reading. For my own camera, I'll just make my own custom chart with the 1.6 offset added in, but I didn't want to post a chart on-line that wasn't calibrated to 0 for everyone else.