The GetDPI Photography Forum

Great to see you here. Join our insightful photographic forum today and start tapping into a huge wealth of photographic knowledge. Completing our simple registration process will allow you to gain access to exclusive content, add your own topics and posts, share your work and connect with other members through your own private inbox! And don’t forget to say hi!

Converting electronic shutter lens to copal 0 mechanical?

Will Deleon

Member
Hi all,

I just acquired a couple Rosenstock digital lenses that are mounted on rollie electronic shutter. I was wondering if I can just remount / screw the lens elements to a copal 0 mechanical shutter?

Thank you in advance.
 

anyone

Well-known member
Hi Will,
most likely you can, but you may not get the best optical performance as the spacing between the lens cells may differ slightly. I did it with a Sironar Digital 90mm lens (although from a Schneider Electronic Shutter) and had to send it to Rodenstock for optimal shimming. The difference before/ after shimming is noticeable. Also the aperture scales of your shutters are most likely off. Rodenstock also can correct this.
 

Will Deleon

Member
Hi Will,
most likely you can, but you may not get the best optical performance as the spacing between the lens cells may differ slightly. I did it with a Sironar Digital 90mm lens (although from a Schneider Electronic Shutter) and had to send it to Rodenstock for optimal shimming. The difference before/ after shimming is noticeable. Also the aperture scales of your shutters are most likely off. Rodenstock also can correct this.

Do you remember what the fee was to do this? Wondering if it's just better for me to find the correct version of the lenses I want.

thanks!
 

Boinger

Member
I have done this exact thing I had a Schneider 150mm digitar on a roller shutter I took it off and swapped it with a copal from a rodenstock 90mm. It's pretty easy to do and minimal fuss.

Yes there can be a difference in optical shimming but you can always experiment with various amounts of shims to see what is optimal not very hard. Most have 1 2 or 3 shims. An easy technique to see if it will benefit you is unscrew the front element from the copal slightly so it will move outward this can simulate shimming and you can see if there is any change or benefit for you.

The aperture scales I ordered from skgrimes that works on large format lenses for $118 and I got the correct scaling. Changing the scales is just 2 screws.

Very easy and I would do it again if I needed too.

Honestly if you can't find copals you can put it on a aperture only mount.
 

Will Deleon

Member
I have done this exact thing I had a Schneider 150mm digitar on a roller shutter I took it off and swapped it with a copal from a rodenstock 90mm. It's pretty easy to do and minimal fuss.

Yes there can be a difference in optical shimming but you can always experiment with various amounts of shims to see what is optimal not very hard. Most have 1 2 or 3 shims. An easy technique to see if it will benefit you is unscrew the front element from the copal slightly so it will move outward this can simulate shimming and you can see if there is any change or benefit for you.

The aperture scales I ordered from skgrimes that works on large format lenses for $118 and I got the correct scaling. Changing the scales is just 2 screws.

Very easy and I would do it again if I needed too.

Honestly if you can't find copals you can put it on a aperture only mount.
Thanks for the reply. So it's not as complicated as I thought. Are the shims easy to source? I would love to just do aperture mount, but I use strobe lighting 90% of the time and P1 E shutter still can't compete against a mechanical shutter. Thanks for all the info.

Will
 

Will Deleon

Member
I believe they are fairly easy to find.

Skgrimes would by far be the easiest place to get shims. And they would already be sized for copal 0 vs a custom shim company.

There are many places that sell shims specifically for optical uses.

I would also recommend a quality lens spanner tool.

Like this is the one i use:

Thanks for all the help. I'll reach out t them and grab more info. I also reached out to Rodenstock and see what the process is just in case.

-Will
 

buildbot

Active member
Slight distraction, but if one were to try to make this process of shimming lenses rigorous, what test chart is best to use for computing MTF that's somewhat affordable?
 

rdeloe

Well-known member
If somewhat affordable means "free", there's the 2010 version of the ISO 12233 test chart: https://www.graphics.cornell.edu/~westin/misc/res-chart.html

It's rather low res for modern digital cameras. That Cornell link has links to companies that sell more contemporary charts.

As an aside, Schneider and Rodenstock would have used a chart like the free one -- or an even less detailed one -- to do their shimming and calibration when many of the lenses we're talking about were new. Of course sensors are more demanding today than in the early 2000s, making this chart somewhat less useful.

I've been using a high quality printout of the 2010 chart for years now to evaluate lenses without a lot of test equipment beyond a sturdy tripod, careful levelling, and thorough examination. I'm sure Rodenstock would have a much more professional setup. Then again, I'm reminded of a story Roger Cicala from LensRentals told of the time he got a camera and lens back from one of the big companies (he wouldn't name it). He sent it in because he didn't think the lens was in good order. It came back with a note from the technician indicating that it had been tested on the company's test bench and pronounced "within spec". The joke was that the technician left the SD card in the camera, and it contained the images from the "test bench", i.e., the bookcase in the technician's office.
 

dchew

Well-known member
From what I understand, the software that calculates MTF simply needs a diagonal contrast step. I’ve never used the software. I prefer Jim Kasson’s recommended process of just printing any target and shooting it from a reasonable distance in 9 different spots across the image. Center, four corners and the four spots along the middle of each edge. Just swing the camera around to position the target for each image. You can see differences across the field with a relatively small target. I use a Siemens star sourced from Jim’s blog site.
Dave

Edit: I also have the chart Rob referenced. It helps if you are trying to quantify the difference.
 

rdeloe

Well-known member
If the goal simply is to evaluate whether or not a lens is better or worse with shimming, and how much, then visual inspect using charts like the 2010 ISO 12233 chart and Siemens stars can get the job done. I've used them for that very purpose when rehousing some lens cells. Test, evaluate, adjust -- rinse and repeat... The hardest part may be finding the necessary shims.
 

buildbot

Active member
Thanks for the info, that's exactly what I wanted to know - I've swapped a few cells into shutters and would love to test shimming them to see if more performance can be obtained.
 

Boinger

Member
De thread the front element of the lens to simulate shimming slightly. Easy to do and see if it benefits the image without sourcing shims.
 

Geoff

Well-known member
Have always wondered if the setup is so critical, how come there is no hard stop on the threading of the front and bak cells. Or how tight is the right tightness? Maybe the difference is less than ⅛ of a turn or so, but one wonders....
 

rdeloe

Well-known member
Have always wondered if the setup is so critical, how come there is no hard stop on the threading of the front and bak cells. Or how tight is the right tightness? Maybe the difference is less than ⅛ of a turn or so, but one wonders....
I think it matters more for some focal lenses and applications than others. For example, some of the Schneider-Kreuznach industrial version lenses I like to use have cells glued in at the factory, and special marks to show the best azimuth. Presumably they're being used wide open for very critical applications. My copies, in contrast had cells that I've taken out of the aperture mount many times and re-installed. I turn them finger tight, but that's it -- and forget about critical azimuths. For regular photography, I'm not seeing a difference, especially at f/11, but also wide open.

Long story short, before I sent a lens back to the manufacturer, I'd try it myself.
 
Top