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08-03-2007, 06:19 PM   #1
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2x tele good?

So today i took my camera to the woods for the first time since i got it. Started doing some wildlife pix and realized that my zoom jus wasnt zoomy enough. Its a 28-200 so with magnification from the camera....its 42-300. Just not long enough. So would it help if i got a teleconverter and that would make it 600? Is it recommended. I just dont have the money for a big expensive lens and the less lenses i have to carry around the better.

Also, I just purchased a set of close up filters. With these on, will it add to the distance the lens reaches and by how much? Thanks

08-03-2007, 06:56 PM   #2
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#1 RE: 2x Teleconvertor.

Save your $$. :P Unless you get a really expensive teleconvertor (i.e. OEM Pentax, Vivitar 2X Macro) don't bother. The degradations in image quality and light loss are not worth it.

#2 RE: Close Up Filters.

The close up filters don't really change your lens reach. A close up filter allows closer focusing and thats it. Its essentially a magnifying glass.
08-03-2007, 06:57 PM   #3
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The close up filters will reduce the distance your lens reaches - in fact they will prevent it from focusing to infinity at all. They will allow you to focus on much closer objects though. Keep in mind that unless they are very expensive achromatic closeup lenses, they will degrade image quality. I found that anything more than +4 diopters with my Tiffen filters was unacceptable, and the +4 alone was "meh". Extension tubes are the best for image quality, but nearly all of them will eliminate autofocus (nearly every macro photographer uses manual focus anyway), and many will eliminate auto aperture which means you will have to go full manual for exposure on your camera (many macro photogs go full manual exposure also.) Extension tubes that do not allow auto aperture (basically anything less than $100 a set unless you get lucky on fleabay) will also fail with any of the DA lenses that don't have an aperture ring - they will stop down to their smallest aperture size.

Keep in mind that a 2x TC will double your lense's f number. i.e. a lens that is f/5.6 at 200mm will become a 400mm f/11.2 lens. Also, as far as TCs go, "garbage in, garbage out". If your image quality at 200 is not very good, the TC might not actually help that much. Many people go with 1.4x TCs as a compromise - they are smaller, don't increase your aperture so severely, and work better with marginal lenses. (Which most cheap lenses and nearly all "superzooms" are.)

I just got a 1.4x Tamron TC yesterday. I haven't had a chance to really try it, but so far it seems to perform well with my Tamron 70-300. I haven't tried seeing if it can autofocus in daylight yet. Officially most cameras will experience severely degraded autofocus performance if the f number is greater than 5.6 by very much, and an f/5.6 lens with a 1.4x TC will become an f/8 lens. Some people have had decent AF performance with the Tamron and f/5.6 lenses despite this. A 2x TC combined with an f/5.6 lens is pretty much guaranteed AF failure, you will have to focus manually.
08-04-2007, 06:01 AM   #4
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It's never long enough

Hi,
Please excuse me if my assumption that you are fairly new to photography as I am is wrong. When shooting wildlife regardless of what you have is never long enough, sharp enough, or fast enough. I'd be willing to bet that is even true of the guy that has a 500mm fix focal high priced lens.

So here are some compromises that make sense to me and if I'm wrong somebody should jump in and say so. A 28-200 lens will most likely be soft at the 200mm end. If you used a fixed focal 135mm lens and cropped it to the FOV you get out of your lens at 200mm, the 135 image will be sharper. You could get a SMC M 200mm f4 screw mount for less than $100, crop the living daylights out of it and have a sharper image than most 400mm zoom lenses. Since it is a prime you might be able to even use a 2x teleconverter with it. Just my 2 cents.

Regards,
ken

08-04-2007, 06:40 AM   #5
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QuoteOriginally posted by Entropy Quote
Keep in mind that a 2x TC will double your lense's f number.
I thought they added 2 stops, which is not as bad as doubling it - thus it adds 2.8 to it (f5.6 becomes f8.4).
08-04-2007, 07:39 AM   #6
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QuoteOriginally posted by bonovox Quote
I thought they added 2 stops, which is not as bad as doubling it - thus it adds 2.8 to it (f5.6 becomes f8.4).
Nup, doubles both focal length and f-stop.
08-04-2007, 07:46 AM   #7
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2 stops is not the same as 2 f/numbers. I had the same misconception for a while.

1 stop is half the light, and this is proportional to 1/(f number) squared.

i.e. an f/1.4 lens lets through twice as much light as an f/2 lens. (The f number is the focal length to diameter ratio by the way - that's why it doubles with a 2x TC as you've doubled the focal length without increasing lens diameter.)

Similarly, an f/5.6 lens lets through twice as much light as an f/8 lens, thus f/5.6 is actually one stop from f/8.

Also note one current limitation of teleconverters on the K10D and K100D - They do not change the focal length reported by the lens to the camera, so the SR system will not work as well as it could when a TC is used because it thinks you have a 300mm lens when you really have a 420mm lens (for a 1.4x) or a 600mm lens (for a 2x). SR will still improve things as the camera thinks the lens is too short and will undercorrect instead of overcorrect, but it won't be acting at peak performance. (Edit: If you're using the TC with a manual lens this won't be a problem though.)
08-04-2007, 08:15 AM   #8
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Whatever lesn you have you need a hide for wildlife. Your result will improve drasticly if you spent your Tc mony on a hide.

Ill shoot litle birds in my garden at a distance of about 2 meters/yards with my F*300/4.5.

Guido

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