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Old Sunday 8th December 2013, 20:03   #1
birderk
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Test: Big scopes vs big lens with the Kenko Lens2scope and Live View

I finally got around to doing a test I have been meaning to do for quite a while. A few years ago I got interested in photography and purchased a Canon 400 mm f/4 DO lens. It's a great camera lens and because of the DO technology its quite light--about 2 kg. Because I often take walks to get to birding locations, it is often not possible to carry both the lens and my Nikon 82 Fieldscope--so I always was wishing there was an easy way to turn the lens into a scope. About a year ago a friend alerted me to the Kenko Lens2Scope which turns lenses into a scope with a 10mm eyepiece. http://www.bhphotovideo.com/bnh/cont...=REG&A=details My 400mm lens becomes a 40x scope or with a 1.4x or 2x teleconverter a 56x and 80x scope. Unfortunately, this adaptor provides an extremely narrow field of view, has lower contrast than the Fieldscope and focusing with the canon focus ring is extremely critical--it's not going to provide an experience which birders will fall in love with. None the less, the resolution seemed to be quite good. I decided to test this against the my Nikon 82 Fieldscope. Of course, my Canon 7D has its own alternative for viewing which is using live view on the screen.

For the test I used the Nikon 82 Fieldscope with the 25-75X zoom. I have star tested this scope and the star tests seem good to my eye. I am not claiming it is an absolute cherry but I don't think the view is compromised in any way. I haven't star tested my 400mm lens with the adaptor. But I believe the Kenko adapter may introduce a small degree of astigmatism after doing this test. It probably would be possible to get a slightly better sample of the Kenko adapter.

For the test I placed a US $1 bill at a distance of approximately 9.75 away from the scopes. Lighting was artificial and kept a low level which I thought would approximate dusk birding conditions. I compared 4 methods of observing the target: the fieldscope, the canon 400mm DO with the Kenko Lens2scope with and without teleconverters, the canon 400mm DO with the Kenko Lens2scope with live view on the 7D with and without teleconverters, photos from the Canon 400mm DO and 7D with and without teleconverters.

Nikon Fieldscope:
I felt the resolution with the Fieldscope maxed out at about 60x perhaps due to the low conditions--zooming to 75x yielded no more detail. The "E Pluribus Unum" mark on the bill was clearly visible at all powers. Above that mark there is a curl and within that they are series of fine broken lines. These lines are in fact broken with the fieldscope I scope make out the lines at 60x but I could not make out the broken spaces between the lines. These lines appeared solid through the scope.

Canon 400 mm DO and Kenko Lens2Scope.
As with the Fieldscope the "E Pluribus Unum" mark on the bill was clearly visible at all powers (40x, 56x, and 80x) and the fine broken lines appeared as solid lines at 56x. I could not make out additional detail at 80x and it seems 56x was the max of the resolution. Interesting, I felt details were clearer in the fieldscope at 40x perhaps due to higher contrast. On the other hand, at 56x I felt the detailed appeared clearer in the 400 mm DO than at equivalent power in the fieldscope--perhaps due to the larger exit pupil. The 400 mm DO has a 100mm objective size vs 82 mm. In practice there was no difference in resolution between the two.

Canon 400 mm DO and 7D live view.
Using live view and zooming in 10x in live view with the 1.4x teleconverter on the lens I was clearly able to read "E Pluribus Unum" on the screen however I was not able to see the any lines on the curve. Using the 2x converter did not yield additional detail. Live view showed less detail than either the Fieldscope or my lens/kenko combination. I should add that using live allows me to activate image stabilization on the lens which does steady the image which might be nice in a breeze or handheld.

Canon 400 mm DO and 7D.
I took a serious of many photos with and without both teleconverters at various f-stops, shutter speeds, and ISO levels. In none could I read "E Pluribus Unum" after blowing it up. Obtaining good sharp shots was difficult to the low shutter speeds and high noise needed for the shots. It was a surprise to me that I could see more detail through live view on the screen than by taking photos and blowing up the image.


Conclusions:
1) Resolutions of the lens with Kenko scope is fairly scope--at least at the level of the Fieldscope. Since it is quite small and light I will definitely continue carrying it in my pocket on some long walks with my camera and lens as opposed dragging along the Fieldscope as well.
2) Live view could not meet the level of resolution that could be obtained visually through either.
3) Live view provided more resolution than simply taking a photo and zooming in. This was a big surprise for me! This might change in better light conditions which would allow faster shutter speeds and lower ISO.
4) The resolution through a bigger telephoto lens like the 500 or 600 mm f/4 must be really impressive. Reason enough for me to consider purchasing one of the super telephotos? If they were a little less expensive, definitely yes.
5) Surely it would be possible to engineer a better adapter with an excellent 8-24 mm zoom eyepiece? I would love to have such an adapter on my lens.

Brendan
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Old Sunday 8th December 2013, 21:58   #2
looksharp65
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Thanks birderk!

I bought one last April and reviewed it.
http://www.birdforum.net/showthread....99#post2814699

In August I received a Nikkor 300 mm and made the following conclusion:

Quote:
Originally Posted by looksharp65 View Post
The Lens2Scope is but a subpar solution compared to a good spotting scope. It provides a simple and lightweight way to have a spotter in your camera bag by using the telephoto lens you already have. (---) As for now, the Nikkor lens is most suitable for photography since the Lens2Scope cannot make full use of what the lens can deliver.
//L
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Old Tuesday 10th December 2013, 18:56   #3
wllmspd
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I have an arduino and am meaning I try to make an image stabilized monocular using an old canon 125-300mm zoom lens. Found some useful information about possible commands, it's not just a case of sending it 5v! Also I am not sure about how to connct to the pins on the lens without soldering?! Lens2scope performance is not as good as a dedicated scope, but hen it is a lot more portable.

Peter
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Old Thursday 12th December 2013, 13:17   #4
mayoayo
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Birdek.--Thanks for the comparison..always interesting to get first hand field results and no place like BF to find that...
-I wonder if you would be able to attach the prism assembly from the new Nikon Monarch to your 400mm lens...many ,(myself included) are pretty excited about thye possibility of using a hig quality erecting prism in an astro scope,going a step futher in quality of the current available options ,like 1 1/4 amicci prisms, etc..Kowa sells a Porro for their 500mm Prominar lens ,to use Kowa eyepieces ,but both ,the prism and the eyepieces are very expensive...If you can have an adapter made,or someone(nikon)comes with an adapter system that could work in photo lenses or astro scopes,this Monarch prism module,with the astronomy mount could provide birders like yourself the versatility and optical quality you are looking for,,,....
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Old Saturday 21st December 2013, 02:23   #5
birderk
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That is an interesting idea mayoayo. I hope there is some possibility of using the nikon modular system for that purpose but I somehow how doubt that would be designed by nikon.
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Old Saturday 21st December 2013, 15:06   #6
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Not Likely

Quote:
Originally Posted by birderk View Post
That is an interesting idea mayoayo. I hope there is some possibility of using the nikon modular system for that purpose but I somehow how doubt that would be designed by nikon.
Not likely..but you never know..the modular system has a dedicated adapter to attach the objective module to a Nikon SLR camera ,so they understand that observation and photography are shared interests for many users..maybe they can get the idea of reversing the concept allowing photographers that own long quality lenses and that otherwise would not put $ into observation equipment,to spend some money in a nikon piece of equipment and turn their lenses into high end scopes..I will buy the angled prism module as soon as I can afford it,and go from there..See what kind of instrument I end with!
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Old Saturday 21st December 2013, 18:22   #7
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The problem with long lenses is the telephoto group inside, which acts to lengthen the focal length while keeping the outer dimensions moderate.
Spotting scopes do the same by utilizing the erecting prism's long light path. While a telephoto lens naturally is able to deliver a sharp image, the prism unit must have a very short path.
The small dimensions may be challenging, but probably not impossible to produce while maintaining a good image quality.

//L
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