Couple of odd lens issues.......

andy_fozzy

andy_fozzy

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I bought a mint Sigma 50mm F2.8 macro from a smashing chap on here.
A cracker of a lens, but the strange thing is, when the lens is at infinity focus, I can set the aperture at 2.8.
As soon as I focus close to something, the aperture changes! It stops itself down.
If I'm at 1:1 the widest aperture I can set is F4

Not a problem, as macro and F2.8 just doesn't mix as we know! If I'm shooting at 1:1 I'm going to be a minimum of F8

:thinking:

The next one is my Nikon 300mm F4 AF-D
Just received a Kenko 1.4 TC today, again from somebody here, and I though I was supposed to lose an F stop?
But I can still shoot at F4 :eek:

Anyone able to shed some light :thinking:
 
Don't worry Andy, I read somewhere that Nikon take into account the effected change of aperture that increasing magnification causes. Don't ask anymore or your brain will hurt and just go with it ;)
 
Ajophotog said:
Don't worry Andy, I read somewhere that Nikon take into account the effected change of aperture that increasing magnification causes. Don't ask anymore or your brain will hurt and just go with it ;)
Click to expand...

Bloody hell, that's already making my brain hurt :D

Okey dokey, thanks for that bud :thumbs:
 
andy_fozzy said:
The next one is my Nikon 300mm F4 AF-D
Just received a Kenko 1.4 TC today, again from somebody here, and I though I was supposed to lose an F stop?
But I can still shoot at F4 :eek:

Anyone able to shed some light :thinking:
Click to expand...

Because a non reporting 1.4 :shrug::shrug: just guessing
 
with regard to the Kenko, you do lose an f-stop, it's just with that tc it doesn't register on the camera the way it does with one of Nikon's own tcs. With the Nikon teleconverters the actual aperture and focal length will register in the exif, whereas with the Kenko it will still show (iirc) those set on the lens without the 1.4x factor.
 
You can buy a kenko that does report the right aperture. I must have same as you, as I used a tc with the lens and it didn't change the recorded focal length or aperture. I would have sold it with the lens had I known you wanted one!
 
The f/number is only correct at infinity focus and when you get down to 1:1 it is reduced by two stops, ie f/2.8 is effectively f/5.6 in exposure terms, regardless of what the camera thinks. It's an inverse square law effect, and Nikon generally reports this (though what happens with third party lenses may be another matter) whereas Canon leaves it unchanged. It makes no odds though, it's only a number and the exposure is the same, and both are equally 'incorrect' in different ways.

Same with the telecon, as said above. 1.4x raises the f/number by one stop and sometimes that's reported, sometimes not. I have a Kenko 1.4x and on some of my lenses the f/number is corrected and on others it isn't.
 
TCR4x4 said:
You can buy a kenko that does report the right aperture. I must have same as you, as I used a tc with the lens and it didn't change the recorded focal length or aperture. I would have sold it with the lens had I known you wanted one!
Click to expand...

Oh knackers!
I didn't realize you had one going. DOH :bang:
 
HoppyUK said:
The f/number is only correct at infinity focus and when you get down to 1:1 it is reduced by two stops, ie f/2.8 is effectively f/5.6 in exposure terms, regardless of what the camera thinks. It's an inverse square law effect, and Nikon generally reports this (though what happens with third party lenses may be another matter) whereas Canon leaves it unchanged. It makes no odds though, it's only a number and the exposure is the same, and both are equally 'incorrect' in different ways.

Same with the telecon, as said above. 1.4x raises the f/number by one stop and sometimes that's reported, sometimes not. I have a Kenko 1.4x and on some of my lenses the f/number is corrected and on others it isn't.
Click to expand...

Thanks Richard (and everyone else).
It all kind of makes sense!
 
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