Although I don’t know any of the manufacturers specifications for this lens, or even the brand name of the lens, I can tell you that this lens is any excellent performer in the range of 1.6x to 2.5x. If you do happen to find one of these on the used market I can highly recommend it. In it’s range the performance of this lens is at a much higher level than a normal consumer market lens like an APO-Rodagon or APO-Componon. The performance of this lens is very similar to a scanner lens with high sharpness and resolution from edge to edge without any distortion or vignetting.
The lens I call scanner lens X small was purchased with another unknown and un-branded scanner lens on Ebay at the same time, from the same seller. The other lens I call scanner lens X is also an excellent performer, you can read a review of the other lens here on Closeuphotography.com: https://www.closeuphotography.com/scanner-lens-x/
Scanner Lens X small LENS SPECIFICATIONS
Lens type: scanner lens
Focal length: 68mm
Magnification Range: 1.6x - 2.5x.
Due to the limited speed of the lens you can see some sharpness loss due to diffraction starting at about 3x magnification.
Barrel Length: 40mm
Barrel diameter: 34mm OD
Working Distance: Very good.
Chromatic Correction: APO corrected
Resolution: Very good.
Sensor coverage: APS-C
Mounting Threads: None
Forward or Reverse Mount: This lens was used in reverse with the white dot towards the subject
Country of origin: unknown
To find the focal length I used this simple formula:
FL = Added Extension / ( New Magnification - Old Magnification )
FL = +28 / ( 1.62 - 1.21 )
FL = 68mm
To measure the speed of the lens used a macro lens and with focus peaking I made an image of the front lens pupil, than another of the rear pupil being careful not to change focus, finally I made the last image of a ruler for reference being careful not to change focus/extension between frames.
F-number = FL / Aperture
F-number = 68mm / 15mm
F = 4.5
2500 pixel Image at 2.4x Magnification
You have to see the image below at the full 2500 pixel size. Click on the image below to view a larger version in a Lightbox viewer, but this will only be the largest size image if your screen/window is large enough. The size of the image sent to your device is based on the screen size. To check the size of the image you are looking at, look up at the URL window at the top of the browser, the address should have 2500w at the end. If the image size is anything smaller you can easily change the number to 2500 manually and press enter to bring up the largest image.
To see an images in a new browser tab, right click, or two-finger press, and select Open in a New Tab or New Window from the menu. You can also right click, or two-finger press, and select Save Image As to save and view the image full size.
2.4x Test: Schneider-Kreuznach APO-Componon HM 45mm f4 macro LENS X VS. Scanner LEns X Small
These are the crop areas, center, edge and corner, for this test the APO-Compon was stopped down to f/4.5, since this is a sharper aperture for this lens and also so that it matches the scanner lenses aperture. Ideally all three areas should have similar sharpness and resolution without any chromatic aberrations.
Before you take a look at these images its important to click on an image so you can examine the the full-size 2500 x 1350 image, the best way to do this is to right click on a PC or two finger click on a Mac and select either download of open in a new window or tab. The image server sends a image size to match the browser window so check the image’s URL, it should have 2500w at the end of the address, if not you can manually type in 2500 over the other number and hit enter to bring up the larger file.
In the first comparison images it’s easy to see that both lenses have no problem producing a sharp and detailed image in the central area. Be sure to look at the micro lettering 1B, 6A, 7A. 5A to the right of the center at the top of the lens and compare both mages, both lenses do an excellent job reproducing these letters.
Sharpness is not the important factor when looking testing and lens, it’s important to compare chromatic aberrations. Look at the lettering 133E40230 HUNB on the left side of the crop area, just about the middle of the image. You can see the pink glow of chromatic aberrations around the lettering and numbers, and along most vertical slanted edges on the SK 45/4 APO lens image. The Scanner lens image shows about 90% less chromatic aberrations and a lot black blacks, where the SK lens has a pink glow around bright areas
High-end line scan lenses like like those from Rayfact, and film scanner lenses, like the Scanner Nikkor ED or Minolta Elite 5400 lens have consistent even image quality across the entire frame from edge to edge without any chromatic aberrations.
Looking at the same 1B, 6A, 7A, and 5A micro lettering in these edge crops the sharpness and resolution is similar to the center so no problems here but the left side of the images tells another story. The scanner lens X Small is consistent from the right to left side. The APO-Componon 45 shows softening on the left side of the crop compared to the right. The softness is not being caused by field curvature, its just caused by a poor design with a small image circle.
In the corners the problems with the Schneider lens are a worse, the APO-Componon 45/4 cannot produce sharp on a on APS-C sensor. You can stop down from f/4.5 to f/8 to improve the corner performance but this causes the overall sharpness in the image to drop off due to diffraction. The scanner lens X Small produces strong, sharp, contrasty corners that would be hard to distinguish from the center of the frame, an excellent job overall.
Camera: Sony α6300, model # ILCE-6300, also known as: A6300
Sensor size: 23.5 × 15.6 mm. APS-C. 28.21 mm diagonal. 3.92 micron sensor pitch
Flash: Godox TT350s wireless flash x 2 with one Godox X1s 2.4G wireless flash transmitter
Vertical stand: Nikon MM-11 with a Nikon focus block
A series of images was shot with each lens in 5 micron steps, and the sharpest image was chosen for center, edge, and corner Photoshop at 100% actual pixel view. All images were shot as a single RAW files and processed in PS CC with all noise reduction and lens correction turned off, all settings were zeroed out (true zero) and the same settings were used for all of the images. All of the images shown here are single files.
In the range of 1.6x - 2.5x, and if you can live without an iris, the the 68 X Small scanner lens is a highly recommended lens for the studio. The images out of this lens are sharper and more consistent across the frame with much better CA control than a consumer market lens like the Schneider APO-Componon 45/4.
The performance of the 45mm APO-Componon in this test is typical, I know since I own 4 of these 45/4 lenses and have tested even more than 4 samples over the years, and the characteristics of a sharp center and small image circle/soft corners is of all the APO-Componons and Componons, and most enlarger lenses like the famous 28/4 Componon. The test results here show that the Schneider APO-Componon 45/4 is not a lens that I could recommend and in my experience having owned four samples is not really an APO lens so your money is better spent elsewhere rather than on this lens.
More information on Scanner lenses
Review of the scanner lens X here on Closeuphotography.com: https://www.closeuphotography.com/scanner-lens-x/
More scanner lens tests: https://www.closeuphotography.com/scanner-lenses