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#12
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In article rq-jvgu.arg,
wrote: On Fri, 4 Mar 2005 wrote: You have to realize that a 2x will use up a lot of light. You need to halve the exposure time, for the same image stability, and you need 2 stops more to get the same exposure. One stop. Nope - two stops. A 1.4x costs you one stop. |
#14
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..::SuperBLUE::. wrote:
How does pixel density influence the resolution at super telephoto? For example: Is it better to buy a: 1. Nikon 8800 with a teleconverter 2.Olympus e300 2x crop factor 3.Canon 350d 1.5 or 1.6 crop factor 4.Panasonic FZ20 with a 2.8/420mm x teleconverter? 5.7mpix consumer camera disassembled and lens replaced with a 35mm slr lens Lens options: 1.Opteka/Exakta/Samiyang/Vivitar/whatever 650-1300mm f/8-f16 lens (1300mm f/8 EFL Olympus) (teleconverter???) 250 Eur 2.100-400 f/5.6 with 1.4x teleconverter 500 Eur 3.80-200 f/2.8 Tamron or Tokina with a 3x Kenko teleconverter 600 Eur + 250 Eur 4.600 mm f/8 mirror 5.50-500mm f/6.3 Sigma with 2x and 1.4x teleconverters 6. A diy project of makeing the lens myself from components (found a front lens 17cm diameter) 7. A telescope with an adapter 6 inch 1200 f/8 refractor 500 Eur + adapter My goal is to get an image similar to the one from 20x50 binoculars or better. 50mm lens is normal 1x, then 1000mm is 20x normal??? Auto focus speed or manual focus feasibility are also important. Canon 300D might be affordable to you. For AF, you need f/5.6 or better. Affordable good lenses include 400/5.6, 300/4, and 200/2.8. All 3 has the same physical lens openning of about 70mm. So with tele converters, they can be effectively the same as 400/5.6, (300/4 + 1.4x or 200/2.8 + 2x), to keep AF. With the 1.6x cropping of 300D, it is equivalent to 640/5.6. If 43mm is 1x (the diagonal of the 36x24 frame), 640mm is about 15x, close to your 20x binocular. If you want more reach than the 15x, you can stack on more TC, 400/5.6 + 1.4x, 300/4 + 2x, or 200/2.8 + 3x (2x + 1.4x). The result will be smaller than f/5.6 so you would lose AF on 300D. You can block some lens electric contacts to fool the camera about TC to retain AF, or use some 3rd party TC that does not transfer those contacts. If MF is OK for you, then 600/8 mirror is OK. |
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