Tamron 23FM25SP

glasslover · Expire: 2013-10-19

Hi!

The Tamron 23FM25SP is one of my favorite adapted lenses for m43 cameras. It is a 25mm f1.4 C-mount lens, intended to be used for machine vision and security, on cameras with 2/3" sensors. It's small, sharp, quick, light, focuses closely, has great definition, pretty good bokeh, and handles very well. The aperture is stepless, like many lenses intended for video. Like many lenses intended for industrial use, both the focus and aperture rings have locking knobs on them to allow use in a high-vibration environment such as a factory.

m43 has about a 2x crop factor, so the angle of view with a 25mm lens like this one is about the same as the angle of view of a 50mm lens would be on a full-frame camera. C-mount requires short registration distance, so it can only be made to focus to infinity on mirrorless cameras like m43 (i.e. not SLRs or DSLRs).

There are only two problems with it for my use:
1. It vignettes pretty heavily, even on a m43 sensor, so it wouldn't be usable on an APS-C sensor like the Sony NEX use; and
2. It's so tiny that no one takes it seriously.

It's only been mentioned by proper model name here on mflenses once before, and that only in passing, at this location.

This is what the lens itself looks like:

Here's a reference to it, including technical details and a link to a datasheet: http://www.sourcesecurity.com/technical-details/cctv/image-capture/lenses/tamron-23fm25sp.html

Here are a few test pictures I took with the lens. All were taken with an Olympus OM-D E-M5 m43 camera. No post-processing other than resizing for this website, and no cropping, the better to show the vignetting:

f1.4

f2

f4

~f8?

~f16?

And here's a shot of an (admittedly small) person, taken with the same lens: