Lens: Leitz Summar 24 mm f/4.5 bellows lens
Vintage: 1950's-60's?
Lens Mount: RMS.
Needed Adapters: I use an RMS to T-mount adapter and a T-mount to Nikon adapter. Both are easily found on eBay.
Preferred Mounting: Normal, reversing not an easy option.
Filter Thread: None.
Street Price: $300-$600 in good used condition. Prices vary a lot online, shop around.
Controls: Aperture setting. The aperture settings are a little cryptic with settings of 2, 6, and 12. Based on measuring the entrance pupil, the 2 setting appears to be f/4.5. The 6 and 12 settings appear be more related to exposure or aperture area. Based on that, I think that 6 is about f/8 and 12 is about f/11. Halfway between 2 and six (I call 4) is about f/6.3.
Aperture: 10 blades.
Basic Function: Requires a bellows to set focus and magnification.
Aperture# | f/number |
2 | f/4.5 |
~4 | f/6.3 |
6 | f/8 |
12 | f/11 |
Extension | Magnification | Working Distance |
adapters | 1.53 | 32 mm |
25 mm | 2.71 | 26 mm |
5 cm | 3.43 | 24 mm |
9 cm | 5.02 | 22 mm |
13 cm | 6.69 | 20 mm |
19 cm | 9.18 | 18.5 mm |
Est. Focal Length: 24.4 mm |
Appearance:


Resolution vs. Aperture:
This lens is at its sharpest and most resolution at f/4.5, wide open. The aperture is a little on the smallish side (large number) for the focal length.
Corner Fuzziness vs. Aperture:
The peripheral fuzziness varies from good at f/4.5 to outstanding when closed down to f/8 and f/11.
Lateral CA vs. Aperture:
This lens shows minimal lateral CA at all aperture settings.
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 Summar 24 shows very good to outstanding sharpness when used at the lowest magnification (less than 5 cm extension). On the bellows, it shows good to fair sharpness.
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 Summar 24 shows good to very good resolution when used at the lowest magnification (less than 5 cm extension). On the bellows, resolution varies from good at the lowest settings, to poor at the highest settings. The resolution is somewhat impaired by the smallish aperture (only f/4.5).
Corner Fuzziness vs. Magnification:
The corner fuzziness id typically in the good to very good range across the magnification range, although it does get into the visible range when mounted directly to the camera.
Resolving Power vs. Magnification:
This graph represents the smallest details that are able to be resolved by this lens at various magnifications. If the number doesn't get smaller as the magnification rises, there is little benefit to going up in magnification with this lens. This situation is also called empty magnification.
The resolving power of this lens loses steam above a magnification of 5:1. This is likely related to the largest aperture of f/4.5.
Chromatic Aberration:
This lens show minimal color fringing in the center (about 0.18 - 0.43 pixel) and minimal on the periphery (0.009 - 0.022%).
There is mild axial CA on out-of focus details (see image below) as shown by a slight magenta fringe on the right and a slight green fringe on the left of the image.
Longitudinal CA:

Image Contrast: Image contrast is just OK, probably related to the age of this lens.
Flare: This lens shows no significant flare during testing.
Distortion: This lens shows no significant distortion during testing.
Image Samples:
About 3.4:1 magnification, f/4.5, focus stack of 33 images, resized:

Pixel level crop from the image above:
There is very good pixel level detail, no problems. The contrast is a little impaired compared to more modern bellows lenses.
About 6.7:1 magnification, f/4.5, stack of 31 images, resized:

Pixel level crop from the image above:
There is good pixel level detail although it is getting a little fuzzy.
Conclusion:
The Leitz Summar 24 mm bellows lens is a pretty good lens when you just look at the images you get out of it. When looked at objectively, it doesn't perform as well as its modern counterparts in many areas, predominantly related to its relatively small aperture of about f/4.5. I would prefer f/2.8 in this focal length range. because of this, the resolution and sharpness suffers at higher magnifications. The contrast is also a little impaired, probably related to a lack of modern lens coatings. This lens does have good lateral CA and longitudinal CA control. There is no focal flare visible, although contrast does improve with good shielding of reflected light the corner sharpness is pretty good at all but the lowest magnifications.
The price is a little high in that these are collectible. More modern used bellows lens can be purchased for a similar amount with a little shopping around. If given a choice I would stick with more modern bellows lens offerings - Leica 25/2, Minolta 25/2.5, Canon 20/3.5, Olympus 20/2 - or go to a 28 mm enlarging lens.