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Comparing Samyang 500mm mirror lens with old 20" Bausch and Lomb

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About this observation
Observer
Peter Anderson
Time of observation
01/12/2019 - 00:00
Object
Night view of street
Observing location
Brisbane Australia
Equipment
Samyand 500mm F6.3 mirror lens, Bausch & Lomb 20" F5.6 telephoto
Exposure
Several seconds
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In the early 70'S I obtained 20" and 40" focus telephoto lenses mounted on old Graflex wooden camera boxes from the Brisbane 'Courier Mail'. The newspaper had moved to 35mm format and was disposing of all their old 'plate' cameras. I had the lenses mounted in 4" aluminium tubes with 35mm camera adaptors. Okay, it is a sacrilege to use a 'plate camera' for the very small 35mm format, but that was the way things were going. The 40" F8 Ross lens (I think this was the brand), from around the 1920's did not really produce suitable images for astrophotography and I passed it on to my friend at the Brisbane Planetarium for the same low price where he used it for some special effects.

When I had bought the 20" lens, I was told it was very good - great for photos of boating on the bay.  It is a Bausch and Lomb telephoto anastigmat 20" focal length F5.6 to F45. Over the years I have taken a number of images with it...until digital came along in the early 2000's and I was obliged to change my camera equipment from Minolta to Canon.

I recently decided to test it against a Samyang cheapie 500mm F6.3 mirror lens, having now mounted a Canon adaptor on it. I used a Canon 70D with the ASP-C sized sensor for both images - This small size is a further insult to a large plate lens. The tests, (at 5.6 full aperture for the B&L and F6.3 for the Samyang,) image an area of roadway cresting a hill 1.9km distant and show that the old lens performs very well, but the lens system is subject to flaring. 

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