Teleconverters

[Chukie]

This might seem like a silly question to some but here go's how do teleconverter's work do they just alter the focal lengh of a lens ie if I used a 100mm lens it becomes a 200mm or isn't it that simple the reason I ask is like most I am on a tight budget so spending hundereds of pound's or even thousands on a new len's is not an option if I want to keep my manhood that is.But I would like to do more photo's of British wildlife and the only len's I have is a Canon 55-250 so stuggle at time's to get close enough
Thank's for any help in advance

[Lancashire Lad]

You are basically correct Chukie.

The only things you need to be aware of are: -

1 - A teleconverter will always make the final image somewhat less sharp than would be the case without it.

2 - A 2x Converter will normally lose 2 x f stops worth of light. For example if the maximum aperture of your lens is f4, then putting the converter on it will effectively only allow f8's worth of light to pass through. So you will get a slower shutter speed for each stated aperture.

3 - If your lens has autofocus, you will undoubtedly lose it when using a teleconverter. Only some of the manufacturers own converters will retain autofocus, and then (apart from a few exceptions) only when used on prime lenses with large maximum apertures.

These things conspire to make decent hand held shots nigh on impossible, so a tripod would be more or less essential.

That said, the results, in certain circumstances can be quite acceptable, and if it's the only means of getting any shot - why not go for it.

As you say it's an awful lot less expensive than the cost of a big prime lens.

Regards
Mike.

[rogpow]

Originally Posted by Chukie

This might seem like a silly question to some but here go's how do teleconverter's work do they just alter the focal lengh of a lens ie if I used a 100mm lens it becomes a 200mm or isn't it that simple the reason I ask is like most I am on a tight budget so spending hundereds of pound's or even thousands on a new len's is not an option if I want to keep my manhood that is.But I would like to do more photo's of British wildlife and the only len's I have is a Canon 55-250 so stuggle at time's to get close enough
Thank's for any help in advance

You're correct that they alter the focal length, but as you say it isn't that simple.
They also soak up a lot of light. Taking a 100mm f4 lens as an example, with a 1.4x converter the lens becomes in effect a 140mm f5.6 lens and with a 2x converter, a 200mm f8 lens. This in turn means you'll have to either shoot at slower shutter speeds or increase your iso to compensate.
The other downside is that even the best converters on the market will soften the image to some extent. The loss of quality will (usually) be greater with a zoom lens than a prime.
They're certainly a valid option if you need more magnification and can't afford a longer lens, as long as you're prepared for the downsides.

Cheers,
Rog

[Jim Ford]

Originally Posted by Lancashire Lad

1 - A teleconverter will always make the final image somewhat less sharp than would be the case without it.

The consensus for the Olympus 1.4 converter is that it has little or no discernible effect on image quality. My experience bears this out.

3 - If your lens has autofocus, you will undoubtedly lose it when using a teleconverter. Only some of the manufacturers own converters will retain autofocus, and then (apart from a few exceptions) only when used on prime lenses with large maximum apertures.

The Olympus 1.4 converter retains all functions across the range of prime and zoom lenses. It's also water and dust protected.

A plus is that a converter takes up little room in the bag.

The downside is, as mentioned, that you lose a stop of light. You also lose a big wad of cash with the Olympus one - it's over £300!

Jim

[dan-fisher]

Thanks for the question and the answers on this. I wanted to ask the very same question.

[Lancashire Lad]

Originally Posted by Jim Ford

The consensus for the Olympus 1.4 converter is that it has little or no discernible effect on image quality. My experience bears this out.

The Olympus 1.4 converter retains all functions across the range of prime and zoom lenses. It's also water and dust protected.

A plus is that a converter takes up little room in the bag.

The downside is, as mentioned, that you lose a stop of light. You also lose a big wad of cash with the Olympus one - it's over £300!

Jim

Chukie - You'll have to spend another few quid on a hammer and some glue as well, if you want to fit this onto your Canon 55-250.

Regards
Mike.

[Jon]

55 - 250mm I am guessing somewhere around f5.6??
If you add a converter it would have to be an independent make, i.e. not a canon - good news it will be relatively cheap.
As mentioned previously you will lose light, so you will be on f8 but to get a reasonable image quality I suspect you may have to stop to 1/2 to 1 stop again.
I think there will be times when you get acceptable images but you will get an awful lot of unsatisfactory ones.
I don't know which camera you have but I would suspect you would need a minimum of ISO 400 and often 800 -so Iwould ask what is the noise like in your camera?
Sorry I don't want to rain on your parade but it is a case of been there seen it done it.
Jon

[Chukie]

Originally Posted by Jon

55 - 250mm I am guessing somewhere around f5.6??
If you add a converter it would have to be an independent make, i.e. not a canon - good news it will be relatively cheap.
As mentioned previously you will lose light, so you will be on f8 but to get a reasonable image quality I suspect you may have to stop to 1/2 to 1 stop again.
I think there will be times when you get acceptable images but you will get an awful lot of unsatisfactory ones.
I don't know which camera you have but I would suspect you would need a minimum of ISO 400 and often 800 -so Iwould ask what is the noise like in your camera?
Sorry I don't want to rain on your parade but it is a case of been there seen it done it.
Jon

The camara I use is the 400D

[Jon]

You could try this:
Kenko 1.4x DG AF Pro 300 Teleconverter, it is probably the best you can get. I guess it would be somewhere in the region of £120-130 - just do a Google.
The camera will give reasonable to good results at ISO 400/800 but ensure you fill that histogram to the right and then this will minimise the noise.
If you don't understand what I have written feel free to contact me I will explain.

Jon

[Gaza]

Hi Chukie
Best advice i can give, is to go to a good camera shop, with your camera and lens, and ask if you can try one first
It may save you, a lot of money

I have friends, who have loaned me their teleconverters, to try on my 400D and 70 - 300mm IS lens
In short, it doesn't work, with auto focus
According to Canon, You can only use teleconverters on their " L " range lens

Unless someone out there knows differently
Please let me know, as i also would desperately love to use one

Just checked out. Your lens stops down at f.4 Same as my 300mm
According to Canon for the auto-focus to work you will need a lens that stops down to f.2.8

The teleconverter, i tried was the Kenko 1.4 DG AF Pro
But if you find one that does work. Please let me know

Cheers