On a recent walk around town I had to get closer to a subject than my lens would allow. Luckily it was a 35mm 2.8 with an M42 to Sony E adapter. So I unscrewed the lens and handheld it just in front of the adapter. Now I was my own variable extension tube with light leaks.
The image did not get super soft and there were no visible light leaks. I then started to play around a little and also tried to get some tilt-effect. This was one of the first tries:
With the super shallow depth of field you can see that the focus is not as straight as usual.
So with free lenses you can mimic tilt and shift lenses and therefore selectively focus your images (and other awesome things tilt-shift lenses can do).
In the last couple days I was thinking about ways to use almost any fully manual lens as a free-lens (yes I know - just hold it in front of the big hole in your camera). But my biggest fear was running around with an easily accessible sensor. Oh, how easy those mirrorless cameras get sensor dust...
There is a company down under which sells a great freelensing kit. Have a look at www.lensbender.net.
They also sell a so called Lenshield. It is basically a glass plate with a bayonet mount. Unfortunately, it is not very economical to order this part from Australia to Austria (those pesky little two letters difference).
So I combined some of my already owned gear to recreate something similar.
I have a reverse mount adapter for 49mm-filter-mount-lenses and coincidently I also have a 49mm UV-Filter. Just combine those two and you have a lens shield. Just keep in mind that your filter should also have a front thread (stackable filters), because you mount it reversed on the adapter.
Please excuse the image quality. I took this and the following with my iPhone because my a7 is currently being serviced.
For those of you who do not know what a reverse mount is: you screw it on the front of the lens instead of a filter. This gives you a lens you can mount on your camera either way. This is often used as a cheap way to get into macro photography. For best results you should use fully manual lenses.
With these parts in place, your sensor is shielded from the dangerous world outside of its camera body.
I tested it a little bit in very dim light, and the results are okay. As soon as you have a stronger ambient light source, the images get very soft and contain light leaks.
One way to overcome this is to use macro extension tubes. These work like a lens hood, but for your sensor. I tried this because on my first try out and about my adapter worked like a "sensor hood" - super convenient. If you use your normal adapter you won't be able to focus to infinity because the distance would be always bigger than the normal flange distance.
As soon as I have some spare time I'll post some test shots of this setup.
For those of you who are gifted crafters: you could also use a piece of tube/nylon/cloth to create a bellows of some sort for your free lens. Glue it to your shield-filter or the reverse adapter and make it detachable on the lens side. Maybe use a pipe clamp on that side.
For the real deal: use a lens mount adapter for your corresponding lens and cut it as short as possible, then glue the bellows system with the reverse adapter to that.
Now you have easily switchable lenses with a full movement bellows mount.
If you try it - let me know!