extender focusing issues

[appletart]

I have a canon 450d, with a sigma 18-250 lens, and my friend has lent me some extenders. Yet when i put them on, the do not focus at all. i also have a tamron wide angle lens, and a canon 1.4 lens, and having same problem with all of them.


any ideas?

 

[dentedshed]

What brand of extender? Got a pic or link to them?

 

[appletart]

it says triplus extension tube if that helps?

 

[chris321]

When you say 'extenders', are you talking about teleconverters or extension tubes?

Edit: we posted at the same time, I see it's extension tubes you're talking about. Do they have contacts running through them? Do any of the focus points light up when you try and focus? And do the lenses actually try to focus and can't, or do they do nothing at all?

 

[appletart]

are contacts the gold bits? if so, yes

 

[iced_jacob]

They may have contacts to send exif info to the camera but no focus mechanism...if that's the case you are stuck with MF unfortunately :/

 

[appletart]

i cant get it sharp with MF either though

 

[iced_jacob]

then you need a set of AF extension tubes..I got the Kenko ones for £80 on ebay and they AF works great

 

[Dogfish_magnet]

i cant get it sharp with MF either though

depending on the lens you use them with you may need to be pretty close to get focus- set manual focus and turn the focusing ring to min distance, then put the lens about 5cm from the subject and move the camera back slowly to get focus

 

[appletart]

no good with moon shots then?

 

[Dogfish_magnet]

no good with moon shots then?

No......there used to reduce the minimum focus distance of a lens

Have a read of this

 

[iced_jacob]

No......there used to reduce the minimum focus distance of a lens

...and as a result the lens loses ability to focus to infinity

 

[chris321]

no good with moon shots then?

Definitely not! For that you want to look at 'teleconverters', they have additional lenses in them that magnify the image created by the lens, but be warned as they'll magnify any imperfections and you'll lose light, and possibly the ability to autofocus. They're only really designed for high-end primes and a few zooms.

The extension tubes will allow you to focus to within a few mm (depending on what lens you have on), very good for macro stuff, less good for the moon though

 

[seriousrikk]

i cant get it sharp with MF either though

Try using live view?

 

[Canon Bob]

......less good for the moon though

Unless you happen to be there

 

[Snapsh0t]

no good with moon shots then?

Depends who's doing the mooning.....