Regarding the gear that we use, my previous blog post was about concentration. You only need a few lenses and they all don’t have to be extreme in terms of focal length to make you happy: 35, 50, 90. Isn’t that all you need?
After that, I decided that I should once go for the other extreme. What about taking an extreme lens for a short photo walk in town. Only this one lens and nothing else, and see if it is any use. My most extreme and debatable lens is a Tamron 500mm f/8 55BB Adaptall mirror lens. I bought it years ago because I … well I kind of like mirror lenses. I also have a small mirror telescope to watch the Moon and planets. The concept of these super-compact “folding” optics is just, in a weird way, appealing to me. Don’t ask. :)
I never got any really good results from the Tamron. Well I hear you say, mirror lenses are crap. The truth is however different. The lens is actually pretty sharp and it is even very contrasty! But all that kind-of-surpising performance comes with several catches that I will list below, and that explain why we all normally never get good results with this type of lenses.
The pictorial results of my 500 mm photo walk
The pictures in portrait format shown above are actually composites, each took 3 single frames (landscape oriented) that were then stitched in post processing. Apart from that, the level of post processing was really super low. Normally I tweak settings like contrast, saturation, vignetting etc. much more in Lightroom than I did here. In other words: These are basically “out of cam” pictures. Yes the Tamron 500mm mirror lens is that contrasty! Yes it does not vignette a lot even right into the corners!
1. Mirror lenses are day-blind
I read that once in a review about spotting scopes (the kind that birders and hikers use). Due to the folded design, all mirror lenses are prone to false light entering the sensor (or eye, in a scope). Even if you use the hood which is mandatory. However, at night things are different. There is, so to speak, just much less false light out there that could harm the picture’s contrast.
So this would be the explanation why my night shots came out that contrasty and punchy, and if I would take pics with this lens during daylight, they’d probably be much more dull. I will try to check daylight performance of the Tamron 55BB out as well and probably re-post …
2. Focusing a mirror lens is a nightmare
After my outing this night, I firmly believe this is the reason why people think that mirrors are crap for photography. I had the lens on a tripod for my night shots. My subjects were not moving at all. My camera had a built-in stabilisation that also helps calm down the viewfinder image. I could use maximum magnification on the screen for precise focusing. And yet, my pictures did not all come out perfectly well. Why? Read further:
3. The focus throw is super-short
In other words: Just touch the damned thing and focus is all over the place. Rotating the lens barrel a single millimeter makes a huge difference. Huge. They had to provide the full range from infinity to 1.7 metres (!) and that’s why it is so overly sensitive. Even on a tripod, touching the focus ring will also cause shake in the magnified image, so you have to wait 1-2 seconds to see if your new adjustment did any good.
4. The depth-of-field is unbelievably shallow
Even between 200 metres and infinity there’s a huge difference in focus. Regarding depth-of-field, this lens rather acts like a 500mm f/6.3 or so – the front lens diameter is about 80mm, a true f/8 lens would have only 62.5mm. The reason that Tamron marks this lens as an f/8 is, of course, the big central obstruction (the black circle that houses the secondary mirror) that takes away light. Note that there also might be some mirror lenses that are a true f/8 by lens diameter and then are actually even slower than that due to the central obstruction.
Anyway, you can’t stop any mirror lens down. It is a fixed aperture lens. So no added depth-of-field even if you would sometimes want it.
5. Use a camera with stabilisation and electronic shutter
Don’t argue with anyone about this one. Just do it. :) Even on a tripod, the stabiliser takes away most, if not all, of the ever-so-slight vibrations that might otherwise ruin your shots. Same goes for mirrors and shutter vibrations. Just avoid them. Put your mirror lens on a tripod and use mirror lock-up and live view mode, or a mirrorless camera. The Sony A7 II only supports electronic front-curtain shutter but that’s okay already.
6. Check if infinity focus works
This might apply mainly for mirrorless camera owners. Most mirror and super telephoto lenses can focus way past infinity to make sure you never run into trouble reaching infinity even with all those T2 adaptors and rings that are often involved. The Tamron 55BB however has a hard infinity stop … it does not seem to focus past infinity.
It is an Tamron Adaptall lens. Mine came with an Olympus OM Adaptall ring. And my Olympus OM adaptor for Sony is not the best – I have trouble reaching infinity focus with most of my Olympus glass and this adapter. This Tamron 5oomm mirror lens is no expection to that. I could not get focus past approx. 300 metres subject distance. This means there were no super-distant shots of the Cologne Cathedral or the city skyline across the vast Rhine gonna happen this night.
Here are two shots that show what kind of sharpness I could get out of my shots on the A7 II. Please note that not all my shots came out that well because I really struggled to get focus perfectly right for every shot. As I said, merely touching the focus ring already throws it out-of-focus, at times …
I won’t say it matches an apochromatic Canon L lens but it surely isn’t that shabby, and would be absolutely sufficient for high-quality gallery prints, if needed. Also sharpness does not fall off too much at the edges or corners of the frame. All in all, I did not expect this kind of performance. And again, there was almost no contrast boost in post production; this is basically “out of cam”.
So – bottom line – I took a weirdo lens out for a walk and came back impressed. That’s one of the joys of trying old legacy glass. And it was fun using such an extreme focal length with no other choice in the bag. :)