Lens: Schneider 28 mm f/4 Componon enlarging lens
Vintage: Current.
Lens Mount: M39.
Needed Adapters: 43-52 mm step up ring, 52 mm reversing ring.
Preferred Mounting: Reversed.
Filter Thread: 43 mm.
Street Price: $35-$100 in good used condition. Prices vary a lot online, shop around.
Controls: This lens only has two controls - aperture preset and aperture setting. The preset ring allows you to set the final position of the aperture as seen in the green window. The aperture setting slider allows you to adjust the aperture smoothly between wide-open (for focusing) and the chosen preset (for taking the picture). The slider has an additional setting, if you move it a notch further, that allows the aperture close the aperture smoothly without the normal preset notches.
Aperture: 5 blades.
Basic Function: Requires a bellows to set focus and magnification
Extension | Magnification | Working Distance |
adapters | 1.90 | 37 mm |
25 mm | 2.78 | 33 mm |
5 cm | 3.37 | 29 mm |
9 cm | 4.72 | 27 mm |
13 cm | 6.21 | 25 mm |
19 cm | 8.14 | 24 mm |
Est. Focal Length: 29.2 mm |
Appearance:


Resolution vs. Aperture:
This lens has its sharpest aperture at f/4.7 and its most resolving aperture at f/4, both very good for the focal length, as most non-specialty lenses tend to have a sharpest aperture around f/5.6.
Corner Sharpness vs. Aperture:
This lens' corner sharpness is a little lacking at the sharpest aperture of f/4.7, although this testing was done at a magnification of about 3:1. That means that it will tend to improve at higher magnification and worsen somewhat at lower magnifications.
At high magnification, you should be able to use f/4.7 with good corner sharpness. If you plan on using this lens at lower magnification of 3:1 or less, f/5.6 or f/6.7 will give probably give you better results. You will give up a little resolution and sharpness by closing the aperture a notch or two.
The peripheral fuzziness is not particularly obvious during imaging at 3:1 and above.
Note: I would say that any number under 30% is good and under 10% will only be faintly visible on an image.
Sharpness and Resolution vs. Magnification:
This lens has very good sharpness and resolution in the center of the frame - as good as or a little better than most bellows lenses in the 25-38 mm focal length range.
The only issues is that the field flatness isn't as good as most bellows lenses, although that difference is mainly at lower magnification and the difference is minimal at high magnification, as the decreasing field of view tends to significantly improve the corner sharpness.
Performance: Sharpness vs. Magnification:
I have 4 lines that represent levels of performance from outstanding (top) to fair (bottom). This shows where this lens fits into the hierarchy that I have created.
The Schneider 28mm shows sharpness the varies from outstanding at 2:1 to good at the top end of its range, about 8:1.
Performance: Resolution vs. Magnification:
I have 4 lines that represent levels of performance from outstanding (top) to fair (bottom). This shows where this lens fits into the hierarchy that I have created.
The Schneider 28mm shows resolution that varies from a strong very good at 2:1 to fair at the top end. The top end lag in resolution is related to the slightly high f/4.7 aperture.
Resolving Power vs. Magnification:
This graph represents the smallest details that are able to be resolved by this lens at various magnificaitons. If the number doesn't get smaller as the magnification rises, there is little benefit to going up in magnificaiton with this lens. This situation is also called empty magnification.
Very good resolution, although improvements fade a bit above 6:1. That could be improved by shooting at f/4.
Chromatic Aberration: This lens show minimal color fringing in the center (typically < 0.10) and mild in the periphery (0.70 - 1.1 pixel). Anything below 1.0 pixel is good.
Image Contrast: Image contrast is very good, but not quite as high as a high-quality bellows lens.
Flare: This lens shows no significant flare during testing.
Distortion: This lens shows no significant distortion during testing.
Image Samples:
About 3.5:1 magnification, f/4.7, focus stack of 34 images, resized:

Pixel level crop from the image above:
Good pixel level detail for the magnification, among the best out there that I've seen.
About 6.2:1 magnification, f/4.7, stack of 29 images, resized:

Pixel level crop from the image above:
Good resolution for the magnification although a good microscope objective can do better. Seeing quite a bit of fuzziness on this image because of the inevitable increase in diffraction as magnification rises.
Conclusion:
This was the first Schneider Componon enlarging lens that I purchased. I own quite a few now and they are all strong performers (the tops for enlarging lenses as far as I am concerned). This lens has the resolution and sharpness of a good bellows lens, with minimal chromatic aberration and good image contrast. The only weak spot with this lens is that the corner sharpness at low magnification isn't quite as good as a bellows lens. That corner sharpness does improve with closing the aperture a notch or two or with rising magnification, and in the end isn't really much of a problem.
They are commonly available on eBay or at used camera stores relatively inexpensively. I highly recommend this lens as an alternative to a more expensive bellows lens.