Lens Test - Fujinon NW 150mm f5.6 vs Sironar-S

[Ken Lee]

Focus shift is very easy to observe, particularly if the subject is brightly illuminated and at moderate to close distance: Focus wide open, then stop down. After changing the aperture, check if the the target is still in focus. Some lenses exhibit it, others don't.

For a clear demonstration of where I blundered in this regard, click here for a test of several ~210mm lenses. All lenses were carefully focused wide open - on the fine print of the vitamin bottle - then stopped down to f/11 for exposure. The first photo in the series was made with an old Heliar and the focus shift is plain as day.

You can see the same focus shift in this test of three 150mm lenses. Again, the old Heliar shifts focus when stopped down... oops

[jbmia]

Gotcha. I'm going to re-shoot the Fuji and post an update taking that into account. Thanks for the example.

[Drew Wiley]

Most likely neither the lens is NOT the culprit, nor alleged focus shift, unless there is an odd case of mismatched cells. There are plenty of other variables that need to be pegged for an objective test.

[Kevin Crisp]

Focus shift on a modern plasmat? I have never experienced this with any Schneider, Rodenstock, Fuji or Nikkor LF lens. On my protars when used as single elements? Sure.

[jbmia]

Getting ready to re-shoot the Fuji shot Drew. If you list the variables that should be pegged, I'll make my best attempt to account for them. The two variables that I want to re-confirm. 1) Was the Fuji shot in fact taken at F22 2) Was the Fuji shot properly focused. Let me know if there's anything else I'm missing.

[Ken Lee]

Let me know if there's anything else I'm missing.

To evaluate sharpness, a 20 second exposure is best avoided due to potential for vibration while waiting out the time.

With apologies for the over-statement: if I told you that this test of a 610mm APO Nikkor was made with a 10 minute exposure, wouldn't you be skeptical about the results ? (For the record I used the highest shutter speed available on the Sinar Copal Shutter, 1/60 second.)

Try 1/60 or higher if you can: the higher the better. Change location if required.

[jbmia]

Agreed Ken. But that wasn't an issue with the other lens though and they were both shot under the same conditions. I'm going to reshoot the Fuji now in hopes it was something like that and it is brighter at the moment. Either way I do intend to shoot both lenses with a different subject in conditions where I can take a much shorter exposure. I'll post an update.

[Sal Santamaura]

To evaluate sharpness, a 20 second exposure is best avoided due to potential for vibration while waiting out the time...

Agreed Ken. But that wasn't an issue with the other lens though and they were both shot under the same conditions...

In my opinion, given a lack of wind, a stable camera (which yours appears to be) and the fact that your Apo Sironar S result is quite sharp, the 20-second exposure better avoided vibration than one at 1/60 second would have. Any perturbation from the shutter's operation constitutes a much smaller portion of total exposure than it would at the shorter exposure time. Also, your Fujinon result exhibits simple unsharpness, not artifacts of motion blur. By the way, some of the sharpest enlargements I've ever made were from HP5 Plus negatives exposed using the 80mm lens on a Mamiya 7II.

It will be interesting to see what your Fujinon re-test shows. Right now I'm betting that lens is sub-par for some reason. The difference between your initial result from it and the Apo Sironar S is much greater than could reasonably be expected were both samples performing up to at least "nominal" standards for their types.

I predict that, if you test a greater distance, the Apo Sironar S result will be slightly less good, since it's corrected for 1:10. Also, the Fujinon will be just about as bad, since it's probably defective, perhaps as a result of mismatched cells.

[Bob Salomon]

"I predict that, if you test a greater distance, the Apo Sironar S result will be slightly less good, since it's corrected for 1:10. Also, the Fujinon will be just about as bad, since it's probably defective, perhaps as a result of mismatched cells."

Nope. The S will hold its performance at f22 from 1:5 to infinity.

[Sal Santamaura]

...I predict that, if you test a greater distance, the Apo Sironar S result will be slightly less good, since it's corrected for 1:10...

...Nope. The S will hold its performance at f22 from 1:5 to infinity.

Please note that there's a whole lot of room for wiggling in these quotes.

"Slightly" less good doesn't mean anything close to the difference between the OP's Apo Sironar S and Fujinon results. It means that, under extreme magnification, one would likely be able to see a slight difference.

"Hold its performance" doesn't mean there's no difference in an Apo Sironar S' performance between 1:5 and infinity. It means that, given the 1:10 design optimization, performance is up to Rodenstock's standards throughout the specified usable range of magnifications.

Absolutes don't work in this discussion. Even after Rodenstock's production test/acceptance regime, the most appropriate descriptors are relative ones.