# Tele Converters



## Mattieuk (Oct 26, 2005)

I was in my local Jessop’s yesterday looking at lenses, zoom lenses in particular. The guy in the shop was showing me some Sigma lenses (400mm) which were great but costing £600 plus. He mentioned that another option is to use a 2x teleconverter on a 200mm to give you that 400mm reach, but in doing so you would loose a few f/stops. This is where I glazed over as I couldn’t understand what he was on about. 

So my questions are: Is it worth considering a tele converter in place of a new lens and what does loosing a few f/stops mean?

Cheers all


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## -ROM- (Feb 23, 2007)

f/stop is the amount of light a lens lets through i.e. the aperture. So if you have a lens at 200mm with a f/stop of 5.6 if you put a 2 x teleconverter on it you will double the distance so get 400mm (actually closer to 600 as your camera will ahve a 1.5 x crop factor) but you will halve the light getting to through the lens, so f11.

Basically this will render the lens useless in low light situations. So if you were shooting planes on a bright day it would serve you well however if it was a dark day then your images would be either quite dark or you'd have to up the ISO al ot and they'd become very noisy.

Also they will degrade the sharpness slightly and also be more vulnerable to chromatic aberation (the purple lines around areas of high contrast)


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## freon warrior (May 31, 2006)

I have a Nikon 55-200mm 1.4-5.6 on my D40x so would a tele converter would work well with this lens?


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## -ROM- (Feb 23, 2007)

errr i don't think there is a 1.4-5.6, IIRC that lens is 3.5-5.6 in which case the above applies, it would be ok for shooting on a bright day but if you go shooting planes at an air show and it is overcast then due to the high f number and the need for quick shutter speeds it wouldn't be much good.


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## chris_calcite (Jun 16, 2008)

Mattieuk said:


> So my questions are: Is it worth considering a tele converter in place of a new lens and what does loosing a few f/stops mean?


Last question first (as simply as possible). As well as increasing the magnification of a given lens, a teleconverter reduces the amount of light reaching the film/sensor by roughly the same factor. This means that, for example, your camera will need to select a slower shutter speed for any given aperture than it would have to if there was no teleconverter attached. With some of the cheaper DSLRs you may end up with a very dim viewfinder and the camera may even have trouble auto focusing.

On top of that, unless the teleconverter is a very expensive one designed to work with a particular lens (usually called a matched multiplier), it will also optically degrade the performance of your lens. In other words, your pictures will be less contrasty and have lower resolution than the lens usually provides when used alone.

All of the above *may* be acceptable to you depending on the type of pictures you want to shoot, but in short you get what you pay for.

Can you tell I am not a fan  If you really need a long lens there is no substitute for the real thing. Yes, I know they are bloody dear 

C.


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## freon warrior (May 31, 2006)

rmorgan84 said:


> errr i don't think there is a 1.4-5.6, IIRC that lens is 3.5-5.6 in which case the above applies, it would be ok for shooting on a bright day but if you go shooting planes at an air show and it is overcast then due to the high f number and the need for quick shutter speeds it wouldn't be much good.


Thanks rmorgan, here is the lens, am I reading the info wrong?
Clickable


Thanks

Paul


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## IGADIZ (May 21, 2006)

Also for the Canon guys.
Auto focus will function with lenses which minimum aperture equals f/5.6, any lens with a minimum aperture above that will be manual only (except for the EOS 1 series with is F/8). So if you have a 100-400mm zoom which aperture is 5.6 @ 400mm and use it with a 1.4X or a 2X convertor, the lens will switch to manual focus only. There is a hack that you can use, but I've tried this and focusing is painfully slow, basically useless.


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## IGADIZ (May 21, 2006)

freon warrior said:


> Thanks rmorgan, here is the lens, am I reading the info wrong?
> Clickable
> 
> 
> ...


Hi warrior.
Your lens has a minimum aperture of 5.6 @ 200mm. Chances are the auto focus will be rendered useless by using a 2X converter, also 2x convertors, can't be used with some lenses check the user manual of the lens and convertor to make sure it is compatible.


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## freon warrior (May 31, 2006)

Ah! Got it thanks:thumb:


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## Mattieuk (Oct 26, 2005)

freon warrior said:


> I have a Nikon 55-200mm 1.4-5.6 on my D40x so would a tele converter would work well with this lens?


I was told you need this one so as to ensure the A/F system works


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## IGADIZ (May 21, 2006)

Mattieuk said:


> I was told you need this one so as to ensure the A/F system works
> 
> http://www.amazon.co.uk/Nikon-Tc-20E-Af-S-Teleconverter-Ii/dp/B0000BVDZI/ref=pd_sbs_ce_2


Please read this post in full.
The manual can be found Here.

*Usable lenses*
Nikon AF-S Teleconverters are designed exclusively for use with AF-S and AF-I Nikkor lenses.
• *Following lenses cannot be used with the AF-S Teleconverters TC-14E II/TC-17E II/TC-20E II *(The rear
elements of the lens will touch and may damage the elements in the teleconverter.):
AF-S DX 12-24mm f/4G IF-ED 
AF-S 17-35mm f/2.8D IF-ED 
AF-S DX 18-55mm f/3.5-5.6G ED 
AF-S 24-85mm f/3.5-4.5G IF-ED
AF-S VR 24-120mm f/3.5-5.6G IF-ED
AF-S 28-70mm f/2.8D IF-ED
AF-S DX 17-55mm f/2.8G IF-ED
AF-S DX 55-200mm f/4-5.6G ED
AF-S DX 18-70mm f/3.5-4.5G IF-ED

• *Autofocus cannot be used with the AF-S Teleconverter TC-17E II and TC-20E II attached with the
following lenses:*
AF-S VR 200-400mm f/4G IF-ED 
AF-S 300mm f/4D IF-ED 
AF-S 500mm f/4D II IF-ED 
AF-S 500mm f/4D IF-ED 
AF-S 600mm f/4D II IF-ED
AF-I 500mm f/4D IF-ED
AF-S 600mm f/4D IF-ED
AF-I 600mm f/4D IF-ED

• Vibration Reduction function can be used with the VR (Vibratioin Reduction) lens used with the F6, F5,
F100, F80-series/N80-series*, F75-series/N75-series*, F65-series/N65-series*, D2-series, D1-series,
D100, D70-series or D50 camera body.
• When the AF-S Teleconverter TC-17E II attached with the AF-S 300mm f/2.8D IF-ED or AF-S 400mm
f/2.8D IF-ED is used with the F6, F5, F100, D2-series, D1-series, D100, D70-series or D50 camera body,
focal length of the shooting data is not displayed correctly (it is displayed correctly with the AF-S
300mm f/2.8D II IF-ED and AF-S 400mm f/2.8D II IF-ED).
* The Nikon N80-series, N75-series and N65-series are sold exclusively in the U.S.A.

Hope this helps.


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## -ROM- (Feb 23, 2007)

TBH i would leave the tele converters alone mate. They aren't up to much on a number of fronts. I would just bite the bullet and get the lens you need. I would rather spend £600 on a good 400mm lens than £300 on a crap TC, i know it is double the price but at least you're getting value for money and something that will serve the purpose you want without the compromises!


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## g3rey (May 3, 2008)

^^^ Can't agree more. See if you cannot hire/borrow a lens for a day and see how you get on.


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## Mattieuk (Oct 26, 2005)

rmorgan84 said:


> TBH i would leave the tele converters alone mate. They aren't up to much on a number of fronts. I would just bite the bullet and get the lens you need. I would rather spend £600 on a good 400mm lens than £300 on a crap TC, i know it is double the price but at least you're getting value for money and something that will serve the purpose you want without the compromises!


Your right mate:thumb: been doing some reading up while at work. I'll start saving my pennies


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## magic919 (Mar 11, 2007)

rmorgan84 said:


> f/stop is the amount of light a lens lets through i.e. the aperture. So if you have a lens at 200mm with a f/stop of 5.6 if you put a 2 x teleconverter on it you will double the distance so get 400mm *but you will halve the light getting to through the lens*, so f11.


I think 2 stops is a quarter of the light. f/8 would be half the light.


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## -ROM- (Feb 23, 2007)

magic919 said:


> I think 2 stops is a quarter of the light. f/8 would be half the light.


Yeah you're right mate, my mistake it's quarter of the light, but the rest of the info still stands, just me making a slip up in my wording!

Inverse square law has always been a bit tricky!


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