hello

[mikeC]

I would just like to say hello, just found this forum while trying to find the answer to a question using the all knowing Jeeves.

I hope i dont bore people to much with all my newbie questions :)

ok.

I have just got myself a nikon d50 to join the ranks of DSLR users anda couple of lens.

What i was looking to find out is, how much do these 2x telephoto convertors that are available on ebay and the like, reduce the quality of pictures.

I understand that you have to focus manually with them on, but if one changed a 300mm max range into a 600mm or a 900mm then Having to manually focus is an aceptable compromise, but how much is the quality drop.

I also read somewhere that they drop you aperature by a couple of stops, so would I be right at thinking a 4.0-5.6 70-300mm lens would become something like an 8.0 aperature with a convertor on?

thanks in advance

[coldrain]

A 2x tele convertor crops the center of the lens. If you for intance have a Nikon 70-300 f4.5-5.6 G or ED, lenses that have not a very high resolution at 300mm already, the 2x tele convertor will show that unsharpness 2x enhanced.
In short: with lenses that you already reach the limits with with your D50 resolution wise, the 2x tele will cut the sharpness in half again.

The reason you will lose AF is because the TC will crop the center... so only the light that was originally in the center will be spread over the sensor. This is why they say you lose 2 f-stops in light.
The camera needs around f5.6 to focus reliably. This does depend on the light conditions and subject contrast, of course. If you add two f-stops to f5.6 you get f11, not f8.
With f11 worth of light it gets VERY difficult for your AF sensors to detect when best focus is reached.

So, yes, you can use them. If you have one of the above mentioned Nikon 70-300's do not expect all that great results. And also get a tripod, with those lengths and such little light, the shutter speeds will need some help.

[mikeC]

A 2x tele convertor crops the center of the lens. If you for intance have a Nikon 70-300 f4.5-5.6 G or ED, lenses that have not a very high resolution at 300mm already, the 2x tele convertor will show that unsharpness 2x enhanced.
In short: with lenses that you already reach the limits with with your D50 resolution wise, the 2x tele will cut the sharpness in half again.

The reason you will lose AF is because the TC will crop the center... so only the light that was originally in the center will be spread over the sensor. This is why they say you lose 2 f-stops in light.
The camera needs around f5.6 to focus reliably. This does depend on the light conditions and subject contrast, of course. If you add two f-stops to f5.6 you get f11, not f8.
With f11 worth of light it gets VERY difficult for your AF sensors to detect when best focus is reached.

So, yes, you can use them. If you have one of the above mentioned Nikon 70-300's do not expect all that great results. And also get a tripod, with those lengths and such little light, the shutter speeds will need some help.

Thank you for the information, but just to clarify?

my camera has aperature 5.6 and then has 6.3 and 7.1 then 8, then 9 and 10 before 11

so are these 1/3rd stops? and the extender adds 2 full F stops? 5.6 / 8 / 11 ?

[coldrain]

Yes, you have got it. f1 f1.4 f2 f2.8 f4 f5.6 f8 f11 f 16 f22 f32