The subject of this post is a fixed telephoto lens available quite cheaply in M42 mount - the Optomax 300mm f/5.6.
I acquired this lens as part of a bundle with a Pentax S1a SLR body and paid a total of £5.50 + £5.00 P&P for the Pentax body, this lens and a Hanimex 80 - 200 mm zoom. At first, I thought this lens had a large fungal growth in the centre of the front element, but when I wiped the lens with a lens cloth that wiped off, so I'm not sure if it was fungus or just dirt. The one slight issue I have was that the lens mount had obviously been unscrewed from the body of the lens at some point because it was loose, and a screw was missing, but it didn't take much effort to re-tighten the remaining screws and that seems to hold enough to use the lens.
Optomax 300mm f/5.6 telephoto images
The lens is of the simplest possible construction. It has a preset aperture which adjusts from f/5.6 to f/32 with an almost circular aperture hole. I don't know exactly how many blades are involved in the aperture, but it must be something like 12 or 13.
The focusing is smooth but has a poor close focus of only about 4 1/2 feet. The lens itself is long and quite light, of full metal construction and came supplied in a cheapish black lens case. The actual lens elements seem to be coated, although I don't know if that is a single coating or a multiple coating. Although I paid only about £10 for the whole bundle, I've seen examples of this lens on eBay for between £15 and £30 (it's an odd fact, but often it's cheaper to buy a lens with a camera than by itself).
Optomax 300mm Sample Pictures
So the real test is how does the lens perform. Well, below is a small gallery of shots I took one lunchtime as I walked around the countryside local to my house. These are not spectacularly good images - they are simply to show the technical quality of the pictures which the lens can achieve. All these images were taken at either f/5.6 or f/8 on a pretty dull day with a shutter speed of 1/500 or so and shot in shutter priority mode on my NEX 6. This allows the camera to set the ISO for the correct exposure, which ranged from about 400 to 1600.
All in all I think this lens is a reasonable performer. It certainly seems to be better than the only other Optimax lens I own which is a 200 mm f/3.5. It seems to have better contrast than that lens, and better definition and 'punch'.
There was a small amount of chromatic aberrations - particularly when shooting into the sun, but these were easily fixed in Lightroom by choosing a profile of a similar lens (I used a Pentax 300 mm lens) and applying the corrections. The pictures were post processed using my usual post-processing techniques.
