OLPF modification & Effective Flange to Focal distance question.

[Rob Skates]

After the Interchangeable OLPF System modification, is there a change in the number of pieces of glass (filters, clear or otherwise) or the thickness of the glass and or filters in front of the sensor? We have noticed focus issues in post modified cameras. The flange to focal distance was correct prior to the modification with tack sharp focus. After the modification the flange to focal distance was correct yet there were focus issues that were consistent with several lenses. The lenses were all tested on an optical projector to eliminate the lenses as the issue. We noticed the focus issue with two interchangeable OLPF modified cameras. The focus was off with both cameras by the same degree. It could be a coincidental anomaly. We suspect a change to the thickness of the OLPF or the addition of protective glass in front of the sensor etc. This would create a change in the Effective flange to focal distance in the same manner that behind the gate filters did on film cameras. Has anyone else experienced this with their OLPF modified cameras.

 

[Robert Ruffo New]

Cannot be fixed via backfocus adjustment?

Is focal distance uneven across the frame?

 

[Phil Holland]

After the Interchangeable OLPF System modification, is there a change in the number of pieces of glass (filters, clear or otherwise) or the thickness of the glass and or filters in front of the sensor? We have noticed focus issues in post modified cameras. The flange to focal distance was correct prior to the modification with tack sharp focus. After the modification the flange to focal distance was correct yet there were focus issues that were consistent with several lenses. The lenses were all tested on an optical projector to eliminate the lenses as the issue. We noticed the focus issue with two interchangeable OLPF modified cameras. The focus was off with both cameras by the same degree. It could be a coincidental anomaly. We suspect a change to the thickness of the OLPF or the addition of protective glass in front of the sensor etc. This would create a change in the Effective flange to focal distance in the same manner that behind the gate filters did on film cameras. Has anyone else experienced this with their OLPF modified cameras.

It's sound like it's possible during the upgrade and QC your back focus might have been adjusted on the camera itself.

Remove the cap and adjust the back focus accordingly.

I haven't had any issues in this regard, but I regularly check my back focus.

 

[John Marchant]

I expect your back focus just got moved... It's adjustable after all

The OLPF hasn't changed thickness for sure.

 

[Rob Skates]

The focus issue with both cameras was quickly solved with a back focus (depth) adjustment using a DENZ FDC multi depth checker. However both cameras are now set to a depth that is different than prior to the modification. Not a problem, issue or concern. We are just wondering what caused the change. The focus issue was consistent with both cameras, as was the amount of depth change needed to remedy the issue. Our best guess is there was a change to the thickness or number of filters etc in front of the sensor resulting in a change to the effective flange to focal distance. No doubt the Red service tech set the depth as part of the upgrade. If however the new OLPF is of a different thickness that the original one, or additional glass is added, the depth would have to be set differently to compensate.