Samyang 800mm Lens Review:
A Night & Day Companion
The Power of Controversy
The Samyang 800mm MC IF f/8 is a manual focus, fixed aperture mirror lens made in Korea. It is a well-built metal construction styled in black and white. Having no electronics, it reaches a weight of only 946 g. Its compact size makes it easily portable. It has a good grip and lies good in the hand. Every copy of it comes with a test certificate.
The Samyang implements a closed, dust-protected catadioptric design consisting of a large corrector plate in the front, a primary and a secondary mirror and an embedded 4-lens flattener. The optics feature Multi-coated (MC) coatings ensuring high light transmission. Both lens caps are made of plastic. Its universal T2 mount is adaptable to numerous interchangeable lens cameras.
There is an optional 2x teleconverter with T2 threads on both sides, providing extreme telephoto capabilities.
A metal lens hood is also available in the market (Samyang Lens Hood 800mm f8 Mirror SH-105S). It is screwed on the 105 mm filter thread. It has been blackened and fine-textured to prevent internal reflections. It also acts as protection against damage to the front lens element.
If you are a stargazer, many questions are immediately answered when you see it at the first time. It behaves like your beloved Schmidt-Cassegrain telescope.
If you are new to obstructed optics, please take your time to become more familiar with it. Mirror optics differ from refractors in many respects, especially in terms of properties and handling. How the images will finally come out, will mainly depend on your shooting techniques and your photo processing skills.
Personally, I like the color rendition and the bandwidth of the Samyang very much. The photos have a rather cold, neutral look. Chromatic aberrations (CA) are negligible. Its donut bokeh is vivid and vibrant but typical for catadioptric lenses. I find it creative and inspiring but it will definitively polarize your audience. They will either love it or hate it.
The Samyang lens is suitable for shooting distant, non-moving targets. Despite its softness, its telephoto capabilities are impressive and unique once portability comes at first place.
If even more reach is required, a teleconverter might be a choice. However, the usage of inexpensive teleconverters often implies a significant loss in terms of quality and light transmission (2+ EV stops).
It’s a Scope
Handle it in the same way you always do with your other telescopes. Put it on a parallactic motorized mount being accurately north aligned. You need a stable tripod. Try somehow to support your camera on the mount to avoid slipping, since it now holds the entire lens mass. Use a heated dew cap.
Finding your targets
Use a SLR red dot finder that is simply attached to the flash shoe of your camera, to find your targets easily at night. The viewfinder is only helpful for centering the target.
Focusing at night
You need to acclimatize the lens first; 30 minutes should be enough. Finally, focus it on a planet or a bright star using a Bahtinov Mask on the Live View display. The focusing scale on the Samyang is quite accurate, i.e. start with the infinity markings. Focusing is smooth with no backlash or mirror shift. However, the focus zone is very narrow. Be patient. The hot spot does exist.
Taking the picture
Point a bright Messier object and go with ISO2200 and 60s exposures first. After taking some pictures try to stack and process them as you usually do with your astronomy photos.
We are all perfectionists
Unfortunately, my exemplar shows triangle-shaped stars at winter temperatures below 5°C, which is an indication of tensed optics. Since the operating temperature range of my camera is 0...40°C, this issue is not a show-stopper for me. Under normal conditions (>10°C) the stars are beautifully round-shaped and the lens delivers a good image quality.
In general, all mechanics, lenses and mirrors inside a telescope asymmetrically shrink when the temperature decreases leading to unpleasant aberrations in my case. A solution would be to "relax" the optics, or to use mirror heaters, or to simply use it at normal temperatures as I do.
Let us be realistic, nobody should expect flat-field APO capabilities under all circumstances from a 183€ lens.
As every large lens, it needs to be acclimatized before usage. This step may take some minutes. Reaching thermal equilibrium is a prerequisite to achieve its maximum performance.
Contrast & Sharpness
To improve the contrast, the optional lens hood might be a little help. It reduces lens flares, halation, ghosting, and general degradation of the image caused by unwanted light sources. Unfortunately, the lens cap cannot be attached to the front lens, when the hood is mounted.
Stopping down the lens will further improve the sharpness. However, a self-made aperture tuner is required in this case.
Working on a Tripod
To get non-blurred pictures, you need:
a stable tripod,
a gimbal system,
activated mirror lock-up settings, and
a remote release.
Take your time on focusing and use the Live View at max. magnification. Turbulence in atmospheric layers significantly influences the image quality of large aperture lenses. You need to be patient to find the hot spot. Set the ISO as high as it reasonably gets and adjust the exposure time as proposed in the Live View.
You will probably want to forget your tripod at home when going out for photo shooting in a sunny day. Even you deal with a real 800 mm non-VR lens, there is a way out:
Set the exposure time to 1/2000 s or faster. Depending on the situation, you might want to set the ISO at very high levels though. ISO 4500 works fine for me in most cases. A low noise camera body is always a good investment. Shoot in RAW format.
Put your camera on something solid, i.e. on a beanbag, a window frame, a branch, or a rock. Alternatively, you can lean against a tree or a wall.
Hold the lens with both hands. Focus as good as you can. Do not invest more than 5 seconds on focusing.
Hold your camera tight. Now, hold your breath and take 3 photos of the subject.
Examine quickly how they came out. Adjust the ISO. Refocus as good as you can and take 3 photos again!
Repeat the above steps several times.
Evaluate your images on your home PC later. Keep only the best one and delete the rest.
Having remarkable telephoto capabilities, this portable lens is a reasonable addition to your camera bag. While drawbacks like low micro contrast and the missing AF/VR in a classic package are not a secret, they can be excused when faced with its incredible price tag.
At the end of the day, it all depends on you. In any case, you get something timeless for little money. Having owned several lenses to date, this Samyang is simply the most controversial one.
Other much more expensive lenses surely offer better results and a broader applicability. But even you can afford them, they are far heavier and thus less portable.
Finally, one question still remains open:
“How often would you use an 800 mm lens?”