Enlarger Lens Comparison

Thank you for the explanation.

Qualitatively, when the USAF test target is in best focus to show the highest resolution (I guess mainly shorter-wavelength blue + green light?) it looks like there is more red in the image with the Olympus 50mm f/2 than with the Micro-Nikkor 55mm f2:

Olympus 50mm at f/2 (0.5x):




Micro-Nikko 55mm at f/2.8 (0.5x):




Perhaps it's best to compare the Olympus 50mm at f/2.8 rather than f2, although the image is a bit fuzzier:

Olympus 50mm at f/2.8 (0.5x):




These are the usual images for this thread, magnified by a 10x microscope objective. I don't know how meaningful the amount of red color is in these images. You can move the focus and see blue rather than red, but the resolution is lower then.

There's no color filter in this shot. Some of the blue color (and lack of contrast) might be from light leaking in from the blue windows desktop background of the nearby monitors. In this setup, there's quite a bit of daylight between the top of the bellows (where the camera was removed from) and the bottom of the microscope objective.

Here's what it looks like without the microscope objective:



This photo is only a 500% crop (rather than 1000%) so it shows 4x the area of the earlier photos. It's also unclear if the focus point is the same, since you can't focus as well with the huge pixels in the sensor.

Hard to compare with them being a different size.

The big difference in setup may simply be that I'm using a 10x objective vs your 5x. I never used any micrometers or electronic calipers to set things up, so I don't think there's anything overly precise about my setup.

Does your setup allow you to focus using 10x magnified live view on the computer monitor? (10x live view was better than 5x for these tests.)

Here is the beast( my resolution testing set up) with the Oly 80mm attached:





It consists of two Minolta III tilt shift bellows each mounted on focusing rails ( one Minolta another Generic( but the same type). The focusing rails are then positioned on a 200mm (300mm would be much better) double sided Swiss Arca standard rail.

The assembled double bellows rig is then mounted to the copy stand via a Chinese made panoramic arca clamp which is attached to the stack shot focusing rail. The rotating clamp allows me to adjust for level( just in one direction). I can mount the testing rig side ways using some further Swiss Arca rails and a second rotating clamp. That mounting style allows me to adjust for level in both X and Y directions. But it adds too much weight and vibration into the system (when I attach this double bellows set up).

I know from previous testing the amount of bellows extension I need for each objective, so I use the Calipers to adjust the extension on each bellows. ( my most important tool is a note book in which I record those details)

I use the micrometer to adjust the position of the upper bellows so that the microscope objective front element is positioned where the camera sensor would be on the bottom bellows. The set square just ensures the two bellows are lined up so there is a straight image line from the lens being tested through to the camera sensor. I have been using the oly OMD-EM10II for the testing of the last few objectives. Its smaller and lighter than the Sony A7rII and it has smaller pixels so its resolution is slightly better than the A7rII ( but noise is a really annoying issue)

Using the Olympus or the Sony I don't use tethering for the resolution testing. The reason being that, even though the Sony can tether, the 5X or 12.5X manual focus assist combined with the higher screen resolution on the camera makes focusing much easier with the camera than on the computer screen. The Olympus can't tether and it has 14X magnification for manual focus assist.

The weakest points of the rig:
1. The microscope objective it is a cheap generic 5X( but its heaps better than the 10X example I have)

2. The two focusing rails for each bellows. They don't have fine enough adjustment and as I discovered yesterday at least one of them has a tendency to creep when left alone for a while.

3. Weight: the copy stand I have can easily cope with the weight of the rig, but at the magnifications being used the added vibration really is a huge issue. The Sony when used is set to EFCS and I have taken to using the Oly in fully silent mode with full noise reduction( it needs it in this situation). Triggering of either camera is via the stack shot shutter control.

As you can see I mount the resolution slide on an old macro stand( after removing the grey subject glass from that stand). The resolution target is chrome on glass so I need to raise it above the white background to avoid shadows which would make the test image confusing

I finally got around to testing my Mamiya sekor C 80mm macro lens. Its not an enlarger lens. Originally I had purchased it for use as a tilt shift macro lens... but It never really impressed. I have always planned on replacing it with he 120mm macro but never got around to it. I thought I would test the lens to see if it is as bad as I thought and it is. It suffers from CA, and only resolves to Group 6 element 3( 80.6 cycles per mm) which is less than what the sensor is able to resolve.

Dust in the photos is on the targets

That kind of sums up all my experience with the lens. Where other objectives take just the slightest nudge to come into (and out of) focus. This lens drifts into a region of "focus" and slowly drifts out of that same region. There is just no clear point of sharpness. My example is the earliest version and it is possible I have a lemon. I understand the "n" version is supposed to be better but from my reading every one states the 120mm is the lens to get. From my experience ( if it is typical) the 80mm is not a lens to get.