BetterPhoto Q&A
Category: Traditional Film Photography

Tracy A. Emerson		what to buy I'M USING A CANON ELAN 7E AND WANT TO BE ABLE TO REACH OUT MORE . I HAVE A 70-300 SIGMA LENS AND WAS WONDERING TO BUY AN OPTEKA HD 2X CONVERTER OR JUST BUY AN OPTEKA HD 500MM FIXED F8 LENS. I KNOW I COULD REACH FUTHER WITH THE 2X WITH MY SIGMA 70-300MM...WHICH WOULD PRODUCE BETTER PICTURES........ THANK YOU..TRACY To love this question, log in above August 24, 2005

Jon Close		I don't know the Opteka brand, but generally... If the 2x teleconverter fits between the lens and camera, you can probably use it, but be aware that it will decrease the zoom's effective aperture. The f/4-5.6 lens will be effectively f/8-11. You do not need to make exposure adjustment, but the viewfinder will be darker, making autofocus unreliable and manual focus difficult. Inexpensive 2x teleconverters aren't especially sharp, either. Better are the 7-element designs like Kenko Pro-300 or Tamron SP. If it is a 2x teleconverter that screws onto the front of a lens, these are usually designed for digital point and shoots and their much smaller lenses. Even though it may have matching 58mm threads for mounting, it'll likely vignet (dark corners). Re the 500mm f/8 (fixed) lens, this is probably a mirror lens. Also known as reflex and catadioptric. These can be very sharp, but quality of a particular sample varies widely. There are some disadvantages of a mirror lens: (a) out of focus highlights appear as doughnut shapes instead of blurred disks. This can lead to very distracting backgrounds - or a fun "arty" effect depending on your point of view. (b) the aperture is fixed a f/8. Exposure is adusted by changing the shutter speed only. On most cameras the lens can only be used in Manual and Aperture-priority modes. (c) manual focus only, and f/8 gives a dim viewfinder. (d) mirror lenses are best at longer focus distances (~12ft and farther) and progressively less sharp when focussed closer. That said, a mirror lens is very inexpensive and can give decent results. I have one and like it. To get better results one needs to spend quite a bit more for a lens like the Sigma 50-500 EX or Canon 400 f/5.6L. To love this comment, log in above August 25, 2005

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