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05-02-2022, 07:36 AM   #1
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Join Date: May 2022
Location: Basildon, Essex
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Hi all,
Name's Manny, from Essex County, UK.
Started with a Canon 80D & Tamron G2 for wildlife and bird photos.
Then got a 6D Mk2 & Canon 50mm f1.4 second hand.
Discovered the intriguing world of Takumars after talking to colleagues who work with radioactive equipment.
Got a Super-Takumar 50mm f1.4 (S/N: 4111346) stored in a 6mm lead-lined Peli case.
Then found a beautiful SMC 135mm f2.5 (S/N: 7562128) and last week found a Takumar 200mm f3.5 (S/N 767712)
I did read somewhere that a DSLR viewfinder might not always show the same focus as the lens, any tips? (Currently using the lcd screen & focus zoom)
Cheers.

05-02-2022, 09:17 AM   #2
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Welcome Manny

Those "radioactive lenses" don't pose the hazard some assign to them. Most all the radiation is stopped by common materials including the lens casing itself, and any distance between you and the lens does the rest. I wouldn't sleep on a pillow of them, but otherwise wouldn't give it much thought. Besides, after you get a collection of them, you'll be spending more for lead lined cases than for the lenses, not to mention all that extra weight you'd have to lug around.

DSLR viewfinders can be out of whack in terms of proper spacing of the focus screen from the lens mount or a misalignment thereof, and then they don't show the same thing as the sensor sees. If your camera has "liveview" or the like, you can easily check your viewfinder by using a fast lens at maximum aperture and comparing the "liveview" image to what you're seeing through the viewfinder (for a manual critically focused image or test chart). They should match, but in any case, you can trust the "liveview" to be correct since this is what the sensor is actually seeing. If you don't have a "liveview" function, you can do something similar by shooting some shots and manually adjusting the focus until you have a target perfectly focused in the result, and then compare that to what you see through the VF (same shot of course). The latter is more time consuming and tedious but it will let you know if your VF is not performing well.

Anyway, welcome aboard the Pentax forum - many happy returns.

Last edited by Bob 256; 05-02-2022 at 09:24 AM.
05-02-2022, 09:25 AM   #3
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Welcome to the forums!
I'm not sure if the lead lined case is overkill or not for the small amount of radioactivity lenses can have. Only you can decide for yourself, but there are a lot of people who don't worry that much about it.
As for focusing through an optical viewfinder, it should be doable as long as the camera's focusing screen is well calibrated, and any error should be consistent, so feel free to use the viewfinder and see what kind of results you get. It will be harder at wide apertures like 1.4, since the DOF is so small.
I don't know much about Canon cameras, but if you're able to install a split prism or micro prism screen in your model, that helps a lot. Still, the lcd screen with focus zoom will be the best way to get very accurate focus.
05-02-2022, 02:33 PM   #4
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Welcome to the forums from the Highlands of Scotland.

05-02-2022, 09:28 PM   #5
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Hello Manny, welcome from Australia.
05-02-2022, 10:19 PM   #6
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Welcome from New Zealand Manny!
aotearoa
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