Although there is a huge variation in lens designs and capabilities, the fundamental mechanism of the modern lens is generally about the same. However, one distinctly different type of lens is the mirror lens, and this neat set of videos takes a look at them and how they perform in practice.
Coming to you from Christopher Frost, this excellent set of videos takes a look at mirror lenses and how they work in practice. The idea of mirror lenses is to reach super-telephoto focal lengths without the size and weight of a traditional lens design. This is done by using a set of mirrors to reflect the light rays entering the lens, taking them on a longer path before they reach the sensor without actually increasing the physical length of the lens. While this is a clever idea, traditionally, two things have held mirror lenses back. First, because of the circular mirror in the middle of the lens, bokeh balls turn into donuts, which can be pretty distracting. Second, mirror lenses tend to have very slow apertures, normally around f/8 or so. Still, they tend to be a very affordable way to get to ultra-long focal lengths. You can see two more reviews of mirrorless lenses from Frost below:
Have you ever used a mirror lens? Did you like it?
I used a Tampon 500mm f8 mirror lens extensively on a film SLR. In the day it was competent, light and pleasant to use. It had small filters that fit behind the lens on a small screw mount for both color correction and ND included. When digital became a thing, the image quality couldn't hold up beyond 10MP, and it got retired.
Ahh.....? a Tampon lens?? What kind of shots are you taking???and at 500mm????...that's a big Tampon!!!!
Wait till you see the Tampon 600! You won't believe how big that Tampon is.
I wouldn’t recommend that lens. Attaching the filters can get a bit awkward.
hahahaha this is the kind of things that should appear more often.
I never knew mirror lenses existed until I found one at a thrift store, but I could tell what it was right away from seeing telescopes that use the same design. I was so infatuated, I bought it not even knowing what mount it was for - turned out to be a Canon FD lens branded as Seikanon on the barrel, but interestingly the metal lens cap says Sikanon. Typo? I read online that Seikanon was the house brand of a West-coast camera shop (I forget the name) that has since gone out of business. It came with a nice leather case with a UV and two ND filters hidden inside, all rear-mount. I was shooting m43 at the time so with an adapter, this being a 500mm lens, the crop factor pushed it to 1000mm and I found it pretty unwieldy. Kinda fun to mess around with though!
I have one of the sharpest 500mm made and just didn't like it. Without anything to hold on to it just jumps everywhere. That was on my Olympus so that's 1000mm. Might try it on my R6 now that I'm thinking about it. On a tripod it's fine but I don't lug around tripods soooo...
I had a Nikon 500/8. That focal length requires a tripod. The aperture is just too slow for wildlife. It was useful for city skylines and mountains. The adapter for using the lens as a telescope was fun to use. Overall, I think the 1000mm can be more useful. But resolution is limited optically, and being a fixed f/8, f/11, makes them unsuitable for use today.
I have a small collection of mirror lenses. They are interesting for sure. My Tokina 300mm f/5.6 for Micro Four Thirds isn't much larger than some normal lenses.
The good news about mirror/cat lenses: you don't get chromatic abberations with mirrors. That was a big problem in the past with long lenses, so they used to be more competitive with refractive lenses. But modern designs deal with that issue. The bad news: the circular center hole also flattens out the normal peaks of an Airy Disc, causing lower contrast and sharpness than you'd get with a good refractive design.
I have a couple of the Nikon 500mm f8 and 1000mm f11 reflex lenses. They are huge and slow and built like tanks. No plastic. On an APC body, they are equivalent to 750mm and 1500mm. Throw a doubler or two on the 1500mm and your looking at 3000mm or 6000mm. Good enough to read the brand of a security camera or a license plate from a half mile or more, easy. Need a good tripod, and a bright day, but if you take the time, you can get some great pics. They were never very popular with film, it seems, but the higher speeds of digital seem to have given them a second life. I'm not a professional by any means, but I enjoy pulling them out now and then. Great conversation pieces, for sure. People see them and do a double take.