Teleconverter?

Lets say you have an 50mm-200mm lens and you hook up a 2x teleconverter. What would the new lens specs be???

100-400

100-400 - but two stops slower.

mike22490 said:

Lets say you have an 50mm-200mm lens and you hook up a 2x
teleconverter. What would the new lens specs be???

Click to expand...

100-400mm. and 2 fstops slower. and this says nothing about the image quality. there is going to be a dropoff. how much? who knows? could be a lot or could be a little, or anything in between. this would depend on the quality of the original lens and the quality of the teleconverter.

Isent 100-400 the same zoom as 50-200? 4x optical?? So whats the diffrence..... P.S your talking to a nooob.

be it 50-200 or 100-400that is still a 4X zoom. but the 100-400version made with the lens and 2x verter will be 2stops slower at wideopen and any other dialed in fstop. if you your 50-200 is a f2.8 then the 100-400 with 2X converter is a f5.6. this will work, but you are getting into the area in which autofocusing may or maynot still be working. with a small enough fstop a lens looses the ability to autofocus.

this does not mean that the camera dials in a f11.0 and you loose autofocusing. no, since the autofocusing is always done at wideopen fstop. check your camera manual to see where autofocusing stops on your camera.

i have the pentax *istD and the sigma bigma 50-500 lens. with the 1.4 converter it still auto focuses, but once i switch to the 2.0verter then i loose autofocusing; the wideopen fstop is just too small too allow the auto focuser to work.

If its still only a 4x zoom, does the converter make a difference? I dont get all that mm stuff!!!!! I only know optical stufff!!!! LOL

it is still a 4X zoom. but instead of the 4x starting from 50mm then going up 4X; it starts at 100mm and goes up 4X from there.

all lenses are still referenced to the 35mm film size. in 35mm film a 50mm lens was considered the "NORMAL" lens. this meant that the view through a 50mm lens on a 35mm film camera looked like the same view as when you took the camera away from your eye and just looked at the subject with your eye only.

therefore, 50mm in 35mm film is considered 1X. that is it looks the same as your eye sees it. if you go to a 100mm lens in 35mm film the subject now appears in the viewfinder as twice lifesize or 100mm/50mm=2X.

please note that the above is for 35mm film cameras not digital dslr where you have a crop factor.

Thanks sooo much!!!!! Finally im starten to understand!!!! 1 more question now!!! You say 50mm is standard with 35mm film. What is the standard on a 1/2.5 sensor?

mike22490 said:

Thanks sooo much!!!!! Finally im starten to understand!!!! 1 more
question now!!! You say 50mm is standard with 35mm film. What is the
standard on a 1/2.5 sensor?

Click to expand...

Hard to say what's standard, but according to this site a 1/2.5 sensor is actually 5.76 X 4.29 mm. Very small. The sensor diagonal, which is what "normal" lenses are supposed to equal, is 7.2mm. So 7.2mm is my answer.

--
Leonard Migliore

mike22490 said:

Thanks sooo much!!!!! Finally im starten to understand!!!! 1 more
question now!!! You say 50mm is standard with 35mm film. What is the
standard on a 1/2.5 sensor?

Click to expand...

A 1/2.5" sensor is the type of very small sensor commonly used on small compact cameras. A 50-200 zoom (with or without a teleconverter) is a DSLR lens. It's not quite clear where you are coming from...

To try and express some of the (correct) comments above very simply: a 50-200 zoom could be regarded as behaving like a telescope or pair of binoculars with a 1x - 4x magnification range. The teleconverter would just double the magnification and turn this into a 2x - 8x magnification range (still a factor of four between the extremes), but at the cost of cutting out a lot of the light so the image through the telescope would appear darker.

(NB to experienced readers: I know this is a simplistic analogy... but it might help).

Best wishes
--
Mike

if you look at the lens specs of your digicam it may say 5mm to 10mm or whatever, but it will also give the 35mm equiv.

Just subscribing to the topic . . .

--
J. D.
Colorful Colorado



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