Six years ago while pondering the effect of contre-jour lighting through using older optics, I made a spontaneous (and relatively cheap) purchase of a 40-year-old Pentacon 135mm f/2.8 lens. The quality and feel of bokeh (out of focus areas) and circular highlights are largely dictated by the lens's number of aperture blades. For most, this is no more than 9 which means that if you stop down just one stop from, say f/2.8 to f/4, your highlights will no longer be circular but rather (in the case of a 9 bladed aperture) an enneagon! My Pentacon has 15.
And, then there's the aesthetics of the image. Are you wanting to produce an ultra-sharp photograph with maximum resolution and contrast or something a little more expressive? There is certainly a place for both but, personally, I find that once you've produced a handful of side-on images of dragonflies or butterflies with the entire subject in focus against a muted backdrop it all becomes a bit repetitive and soulless. Same technique, different subject, and as stunning as these images are they do tend to leave me a little cold for very often they convey little of the mood in which the subject was photographed or of personal expression.
Using older lenses such as the Pentacon requires a little more care than your average modern-day optic. It's manual focus, lacks auto-diaphragm linkage with your camera body (the aperture is at the front of the lens), and requires an M42 (screw-mount)-Nikon adaptor. As a result, it won't focus to infinity (which is OK because I'm using it for close-ups) and if I want to stop down for increased depth of field I have to focus, first, with the lens wide open (this gives me the brightest image to work with) and then stop down. Again, it's rarely an issue since I mostly shoot at maximum aperture, anyway, for my shallow depth of field images.
Old lenses lack the high contrast, anti-reflection coatings of modern optics thereby producing some really interesting effects as the sunlight strikes the glass.
I love its dreamy, painterly bokeh and ethereal glow it gives to my mages.
Although it doesn't reside permanently in my camera bag, if my intention is to head out looking for close-up subjects I'll bring it along, just in case.
So, if you ever find yourself in a creative funk and are unsure of what to photograph and how, consider purchasing an old lens like this Pentacon. It might just get your creative juices flowing again!
