[Lowell Goudge]

Hey Lowell, how do you find your C90 spotting scope compared to your other lenses? Is it plagued with the usual mirror lens woes? I had a Vivitar 500mm for a short time and it was a real pain to focus because I could barely see the viewfinder and my split microprism aid kept going dark haha. Light fall off and corner softness was really really bad...to the point where I totally forgot about the doughnut highlights.

I find it a little lacking in contrast, but when on a stable tripod, (about a 10 pound vivitar professional with Monfretto ball head, suspending the remainder of my camera gear under it for extra weight) it is usually quite good.

I found that with a lens of this length, there are two issues, specifically with respect to older film cameras,

first, as you point out, the split image and micro-prisms around them go dark. Until I got my PZ-1, I used the mirror lens with a KX which I found second hand, and likes specifically for long lenses, The KX came with different focusing screens (I think at time of purchase) and mine was all ground glass, with no focusing aids, and therefore the middle of the screen did not go dark.

Second, the longer lenses on old bodies did not cover the entire viewfinder (top would go dark) due to physical size limitation on the mirror. I did not notice this with either PZ-1 or digital bodies.

I also used this with a right angle finder, which has since been modified to work with my DSLRs (again details on another posting)

See the image below cropped out of a 35mm slide to illustrate what it can do. I have posted this image before

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Last edited by Lowell Goudge; 07-19-2010 at 05:55 PM.

[daacon]

Dave, I would only use a TC with either a telephoto prime or F2.8 zoom.

I have the instruction sheet for the Tamron 1.4x and 2x TCs and I can confirm it says that autofocus will work only with F4 or faster and that lenses should be at least 50mm in focal length. I've had autofocus work, sort of, at F5.6-6.7 but only under very bright light.

You can try out one of my TC's on your 50-500 if you want. I just acquired an old Takumar 400mm prime and I'll bet that it will give better images with a TC than the 50-500 at the long end.

If I can make another suggestion. It will make a world of difference if you get a really good tripod and ballhead (Arca Swiss, Markins, Kirk, RRS, Acratech). Or, better yet, a good tripod + gimbal mount. At the very least get a monopod if you don't have one.

Let me know by PM if you want to try a TC out.
-George

That is a generous offer George and I appreciate it. I may take you up on it. I have no immediate need (let me rephrase that time haha) in the next couple of weeks - I have a couple business trips with no free time and then some 'personal' holidays where again my free time may be spent at the various watering holes (Vegas baby!) - I like you comment on a good tripod and will start looking around. I have a mid-range Velbon (I think I paid about $60 - $70) and looking to upgrade. Thanks again.

[barondla]

Think the photos MO posted with converter was the Pentax 500 F4.5. A very large prime lens. This lens is about 7lbs. Remember the antenna shots well. They were good.
Have found many times instead of using a converter to just use "digital zoom" in the computer to crop what you want. As long as it isn't over done, say matching a 1.5x converter, it is less loss than the teleconverter! Your K10D makes this more doable with 10MP. Try it.
Big lenses take time to learn. Even good ones get traded off because people don't learn to use them properly. Get the most stable tripod you can. Test it by mounting lens/camera and tapping it while looking thru it. Tripod that takes the least amount of time to "settle down" is the best. If tripod takes more than 2-3 seconds it is hopeless. Practice by shooting a brick wall. If you can't get a sharp shot of a motionless wall, it will never happen in the wild. Hope this helps
thanks
No lens is ever long enough
barondla