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Ich

Exposure Puzzle!

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So among the kit I have a Tamron 55 - 200 lens which is a good performer and now I've got the Canon 18 - 55 fits in nicely!

 

I also have a Jessops x2 teleconvertor which works well with the 55 - 200, that is except that every shot I take is over exposed. Now normally when using a teleconvertor the exposure needs opened up by two stops to allow for the light loss, that's fine. But to get a decent shot I have to manually set the exposure back by nearly two stops to use this combination.

Puzzled

 

(not bad though as it's a Canon APS-C sensor so multiply the focal length by 1. 6 to get the 35mm equivalent giving a 640mm result)

 

 

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Jessops always had over exposure problems but it was over exposure to debt.

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Not sure whether you are purposely over-exposing by 2 stops? If so then it would make sense as your camera will no doubt have TTL metering (through the lens), so it will automatically adjust for the 2x converter, provided the converter has the relevant auto connections on it.

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No the camera is automatically over exposing.

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You haven't got exposure compensation set +2 stops have you?

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You haven't got exposure compensation set +2 stops have you?

 

Nope, having to set it back nearly two

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It's been suggested that the combination of Tamron - Jessops (Kenko) - Canon, has set up some conflict electronically, going to do some more tests tomorrow

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Excusing my earlier jest.

 

Have you checked the apperture is shutting down as the photo is taking. Try settting it on manual to f22 on a slow shutter speed and check the apperture shuts down properly. It might be the contacts or instructions are being interupted as they travel through the teleconvertor??

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Just had a play and it looks as though the "clever" bits are getting confused!

With the lens on it's own all is fine.

With the x2 the lens will not go below F11, again which is fine, but the camera is not setting the exposure time correctly, so my compensating by about 2 steps maintains the status quo. I could do it all in manual as well

 

Just tried it with my 70 - 300 it does the same with that but to a lesser degree.

 

At least now I know so can deal with it

Edited by Ich

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Pleased you got to the bottom of the problem I thought it might be something like that.

 

Teleconvertors have always been a sub optimal solution to a decent long focal length lens. They, due lots of glass elements, refract the image and reduce lens speed and quality quite markedly. I would suggest that a Jessops branded version is not the best optics either.

 

You can get away more with digital as the sensor can be made to compensate much better than film ever did but nevertheless you can't beat a proper focal length lens.

 

They seem at face value a simple solution to save money for telephoto work but in reality regularly disappoint in my view.

 

The real win for you here is there is nothing wrong with the camera.

Edited by Fenester

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Oh I was well aware of the risk when I bought it, but it is an inexpensive solution to provide something that I rarely need.

 

What surprised me was it provided the opposite reaction to the norm when used with that lens

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Out of interest, what did you have to pay for the convertor?

 

I like the look of this one. ....... http://www. amazon. co. uk/Kenko-Teleplus-1-5X-Nikon-Teleconverter/dp/B000KZ77YW/ref=wl_it_dp_o_pC_S_nC?ie=UTF8&colid=195YJEYVDOWV1&coliid=I1DZO4IBC7O1FO

 

On the wish list at the moment.

 

I have about three screw type with the old film camera 2x 4x etc. but putting on a T-mount is to complicated and no electrics of course.

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It was about £80, had it for a while but I've rarely used it. As far as I can find out it is a re-badged Kenko anyway.

I'm trying to sort out a smaller "kit" to carry on days out rather than the largish rucksack I have it all in (or getting the wife to put bits in her handbag) and though the 55 - 200 with the x2 would be useful to give me a large range.

 

Now I've sorted this I'll try in next time I'm out and about.

 

As I recall they do affect the amount of light entering the camera and the additional glass can effect quality (as stated by Fenester) but if the photos are mainly for our own use and we are happy, that's all that matters

Edited by Ich

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As an example these are Church Beck Falls in Wasdale at a range of 1. 65 miles using the 70 - 300 at 300mm with the x2. Of course with the smaller sensor in the camera it works out at 300 x 2 x 1. 6 = the equivalent of a 960mm lens on 35mm and handheld!

 

 

35454_3917152881387_465784551_n.jpg

 

A bit misty and slightly over exposed, but you see the intent

Edited by Ich

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Just done a quick adjust with Windows Gallery. . ;)

 

Noted this info on a Kenco

 

Focal Length Magnification: 2. 0 times prime lens
Depth of Field: 1/2 of prime
lens
Optical Construction: 4 elements, 4 groups
Optical Coating:
Multicoated
Exposure Adjustment: 2 stops
Length: 26mm

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Exposure Adjustment: 2 stops

Yes that has always been my understanding, but to compensate exposure has to be increased by two stops. To find in my case it needed decreased by two stops - that's what confused me

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Out of interest, what did you have to pay for the convertor?

 

I like the look of this one. ....... http://www. amazon. co. uk/Kenko-Teleplus-1-5X-Nikon-Teleconverter/dp/B000KZ77YW/ref=wl_it_dp_o_pC_S_nC?ie=UTF8&colid=195YJEYVDOWV1&coliid=I1DZO4IBC7O1FO

 

On the wish list at the moment.

 

I have about three screw type with the old film camera 2x 4x etc. but putting on a T-mount is to complicated and no electrics of course.

I use the Kenko 1. 4 on my Nikon D80 it works very well,

it also works correctly with my D80 and Kenko auto tubes.

Some converters can touch the rear elements of the lense

they are attached to, the Kenko is fine with my nikkor and

sigma lenses

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That's nice to know. I asked the supplier and they said a D3100 was not compatible because AF would not work.

 

The link above explains this and I get the impression it is. :rolleyes:

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That's nice to know. I asked the supplier and they said a D3100 was not compatible because AF would not work.

 

The link above explains this and I get the impression it is. :rolleyes:

I know I cannot use my nikkor 70-300VR lense with ANY converter

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It does sound like the connections for the aperture control are being lost or misread in the converter. These are usually just linked contacts from the camera to the lens being used so maybe a clean with a soft cloth may help. The actual aperture control for the host lens is done mechanically on my Sony A700 DSLR by a sliding lever but not sure what system Canon use. If similar it may be sticking. The image below is the lever arrangement on my auto extension tubes with the lever arrowed. I presume your converter IS auto iris?

post-55268-0-08707000-1360836665_thumb.jpg

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Try a grey card, or even the Back of your hand, set up the camera.

Take a reading, then repeat holding the grey card a few feet in front

of the lense + converter compare the two take your shot with the

grey card exposure. You could also try the bracketing button setting

+1,+2,+3 and see which is the most pleasing exposure.

I will admit I am very lazy and started to use Auto a lot, but if you try it

you may find that three consecutive shots of the same subject under

the same light conditions are all different! I now use program or manual.

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Capricorn 12, all lens operation is electrical/electronic on the Canon and is working correctly apart from the over-exposure.

 

gumdrop, playing with it if I set the exposure back by 1 2/3 it becomes acceptable.

 

There is no doubt that there is some mismatch with all the different makes of kit but having figured it out for the occasionmal use of the teleconvertor I'll cope!

 

As is often said, "you live & learn"

Edited by Ich

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I use one of these as well as a grey card but I am still working out how to use it properly.

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looks like a flattened out Rubik Cube. ;)

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