First Light: Samyang 800mm catadioptic lens

[baggywrinkle]

At last a clear night to give the Samyang Catadioptic 800mm lens a test.

This lens was bought in Singapore along with T rings to mount it to a Canon and a micro 4/3rds camera.

I tried this on a Panasonic GF2 Micro 4/3rds digital camera mounted on a tripod and up on the upstairs balcony of my house in Shanghai. My Canon 650 and 400D are on their way to the UK.

Though the sky was clear the viewing was not good, the Moon was over the houses opposite mine, lots of light pollution, so bad even in a relatively dark area of our estate not even the brightest stars were properly visible.

As the lens is totally manual for focus and no electrical connection to the camera, focus and timing has to be set manually, there is no apeture control, you are fixed at f8. Another fact to bear in mind as this is not a digital lens and my GF2 is a micro 4/3rd then the true focal lenght needs to be mulitiplied by at least 1.5, to it was working at 1200mm in my estimation.

It is a well made lens, solid and not over heavy and decent resistance in the focus ring.

Even with live view and tthe ability to zoom in on the view this is not an easy lens to focus. It did need trial and error to wait for the wobble to die away on the tripod. More practise needed!

I tried a number of exposures and settled on 1/200th at ISO800, the image has minimum processing. I also set a 10 sec delay to allow any tripod wobble to die away. There is no mirror on the GF2 so no mirror lock was used.

Zooming in on the image reveals that the fine focus needs working on, but no 'donut' was obscuring the Moon. I had heard that some of these catadioptic lenses sometimes suffer from a darkening at the centre of the image.

I tried at various exposures down to 1/25th. On the Moon at this phase the over exposure starts to set in at around 1/40th on this lens.

Overall I am happy, the lens works but it needs more work playing with it and putting it on a better tripod and once in the UK piggybacking on an EQ mount. It is not particularly fast at f8 but with digital cameras the exposure casn be compensated for.

As an indication of the 'zoom' power of the lens 3 other photo's are attached. One shows an overall shot from my hotel in Alamaty (did not get a chance to use the lens there)using the GF2 with a 35mm lens. The second and third show the sign on the top of a building in the middle distance and two tower blocks to the left in the far distance using the 800mm lens.

Some heat haze and heat wobble is showing on the latter two.

[baggywrinkle]

I have now had a couple more clear nights and more of a chance for a good play with the lens and camera.

I am really please with this lens and I think that one of the limiting factors for focusing could be the camera I am using it on.

I made a very simple mod using insulating tape and a small right angle bracket to give me a bit more control on the focuse rather than twisting the focal ring alone. This worked but getting a sharp focus is still a bit of trial and error.

The Lumix GF2 I am using is a micro 4/3rds camera with live view only. It is not like a DSLR so you cannot really 'look' at what you are focusing on. The live view screen is 3'' so small. You can expand the view 2x or 4x but the dot size on the screen is in my opinion the problem. Even trying to obtain a sharp focus and looking close up at the screen the dots limit just how sharp you can make it plus peering myopicaly at the screen with my glasses off.

Am I barking up the wrong tree.

The only way I can prove this means waiting until I am in the UK and can use my Canon DSLR's.