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Lens: Leica Photar 25mm f/2 bellows lens

Vintage: Current.

Lens Mount: RMS.

Needed Adapters: This lens is fairly easy to adapt via a standard RMS adapter. I use an RMS to t-mount adapter and a t-mount to nikon F adapter.

Preferred Mounting: Normal, not reversed.

Filter Thread: None.

Street Price: $500-$900 in good new/used condition. Prices vary a lot online, shop around.

Controls: Aperture setting.

Aperture: 6 blades.

Basic Function: Requires a bellows to set focus and magnification

Extension Magnification Working Distance
adapters 2.31 25 mm
25 mm 3.32 22 mm
5 cm 3.99 19 mm
9 cm 5.49 17 mm
13 cm 7.02 15 mm
19 cm 9.34 14 mm
Est. Focal Length: 26.1 mm

Appearance:

leica photar 25 top view leica photar 25 side view

aperture graphResolution vs. Aperture:

The sharpest and most resolving aperture is about f/3.3 (half way between f/2.8 and f/4). Since there are no aperture detents, you will need to eyeball the aperture setting.

corner sharpness graphCorner Sharpness vs. Aperture:

The corner sharpness is OK above an aperture of f/3.3. If you want really sharp corners at lower magnification, you may choose to use f/4. You will give up a little resolution in the process, but the sharpness is nearly equal to f/3.3.

I was a little disappointed by the less than stellar corner sharpness of this lens.

(Testing done at 4:1 magnification. Numbers at each aperture setting will tend to improve as the magnification is decreased).

resolution graphSharpness and Resolution vs. Magnification:

This lens shows extremely good sharpness and resolution across its usable magnification range of 2.3x - 9.4x. As bellows lenses go, I haven't found one that outperforms this lens in center sharpness and resolution across this magnification range. It is one of only 2 lenses that I have tested so far that have a MTF50 above 1000 lw/ph above a magnification of 3:1.

Corner sharpness is a little below average for bellows lenses. It is not so hot at lower magnifications and pretty good at higher magnifications.

performance:sharpness graphPerformance: 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 Photar 25mm has sharpness performance varying from outstanding at the low-end of magnification to very good at the high-end.

performance:resolution graphPerformance: 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 Photar 25mm shows resolution performance that varies from outstanding at low magnification to good/fair at the high-end.

resolving power graphResolving 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, no problems.

Chromatic Aberration: This lens show minimal color fringing in the center (about 0.05 - 0.40 pixel) and moderate/severe on the periphery (1.30 - 3.80 pixels). Anything below 1.0 pixel is good.

Image Contrast: Image contrast is very good, typical for high-quality bellows lenses.

Flare: This lens shows no significant flare during testing.

Distortion: This lens shows no significant distortion during testing.

Image Samples:

About 3.3:1 magnification, f/3.3, focus stack of 42 images, resized:

sample image

crop imagePixel level crop from the image above:

There is very good pixel level detail, no problems.

About 7:1 magnification, f/3.3, stack of 25 images, resized:

sample image

crop imagePixel level crop from the image above:

There is very good pixel level detail, no problems.

Conclusion:

This is an expensive bellows lens and at least for central sharpness and resolution, performs as you would expect a lens of this caliber - top of the heap. It performs at its best at an aperture of about f/3.3 - half way between f/2.8 and f/4.

The main downfall of this lens is its corner sharpness, varying from not-so-hot at lower magnification to good at higher magnification. Even though the corner sharpness isn't the greatest, it isn't particularly noticeable on images. If you have problems with it, it is easy to bump the aperture up a notch to f/4 and it will get noticeably better.

Chromatic aberration is also so-so on the periphery, but that goes along with the suboptimal corner sharpness. Again, this is not particularly visible on normal images.

It has a usable magnification range from a little over 2:1 to about 9:1 on my bellows - a good range for coin close-ups. The working distance is limited, but typical for the focal length.

It's main competitors that can produce similar sharpness and resolution numbers are the Canon 20/3.5 bellows and Olympus 20/2 bellows. Note that these two lenses are shorter focal length and will tend to have even less working distance than this lens. They are also limited to a higher magnification range due to their shorter focal length. The only way to improve upon these numbers is to go to a microscope objective, and even then you will not improve by much unless you go to a Nikon Plan APO 4x.