Advice on Canon Extenders, please....

RedRobin

RedRobin

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Robin
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I'm a beginner to DSLR but not to photography.

Recently I bought a Canon 70D (crop-sensor) and Canon 70-200mm f4L IS and then Canon 1.4x Extender which I am enjoying immensely and especially as it's so lightweight and portable.

However, when photographing wildlife, lens reach extends the possibilities. I am a serious hobbyist, not a professional. So, I'm wondering if I should buy a 2x Extender (I would only consider Canon) for my 70-200. I realise that I would lose f-stops but as I managed this photo below on f7.1 with the 1.4x fitted, I don't foresee this as a problem, or am I wrong?

HerringGullseaflight_0556.jpg


Thanks for any advice

Robin :thumbs:
 
Yes, autofocus will be gone. The lens becomes f/8 equivalent, and the 70D can't do AF that slow (5.6 is the slowest). Just to be absolutely clear, it's not the f/ratio you set the lens to that counts, it's the effective fastest speed that determines the viability of AF. Comments on the web seem to suggest that the 2x TC is also poorer image quality wise (as you'd expect) than the rather excellent 1.4.
 
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RedRobin said:
I realise that I would lose f-stops but as I managed this photo below on f7.1 with the 1.4x fitted
Click to expand...

The problem would arise when trying to focus. All lenses are wide-open when AutoFocus is in operation, because AF performance is better with more light. One reason why people like fast lenses (with wide apertures) is that they grab more light when wide-open, allowing for better AutoFocus.

Your 70-200 without a TC is f4 - and the AF should be impressively fast. With the 1.4x TC it becomes f5.6 (the amount of light reaching the AF sensor is halved). You'll probably notice the AF is a little slower - especially if the light levels are fairly low.

With a 2x TC your lens becomes a 140-400mm f8. The amount of light reaching the AF sensor is 4 times less than without a TC. Indeed, the amount of light is so low that Canon have decided that most of their cameras won't even try to AF if the maximum aperture is smaller than f5.6 - most of the time it's just not worth it even trying.

You can attempt to fool the camera - tape pins on the TC or use a different TC that lies to the camera. But none of them solve the basic problem - you can't AF properly with insufficient light.
 
SixToes said:
I think you'll lose autofocus on the 70D using a 2x with an f/4 lens.
Click to expand...

....Ah yes, I now remember hearing this some time ago but I have done so many months research before buying anything that I had forgotten!

However, Canon's EF Lenses brochure PDF does list both Canon 1.4x and 2x Extenders as being accessories for the Canon 70-200mm f4L IS and without any AF restrictive note.

I like to override my Autofocus with Manual Focus at times but the AF functions on the 70D are very helpful, especially on tracking, so I wouldn't want to compromise that. In the excitement of trying to grab a good shot it's easy to forget what glass you are looking through and it would be frustrating to lose the option of AF as it's simply a switch on the 70-200.
 
Hey, thanks guys! (y) - You posted some very informative replies while I was writing my last post #6!

I am really enjoying my 70-200 both with and without the 1.4x and find it far more practical than I expected to. 6 hrs walking about 6 miles and shooting over 160 shots with it around my neck was easy-peasy. I suppose that my satisfaction with the Canon 1.4x III made me wonder about the 2x as an additional practical option.

My 70-200mm f4 + 1.4x on my 70D becomes 98-280mm f5.6 when I want it to be. Depends what you are shooting of course.
 
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I did over the summer use a 70-200 F4 with a 2x MKIII convertor briefly as more of an experiment than anything else, at Duxford while I was working. I think it was the Sabre went up and called for a fly by so I quickly grabbed my bosses 70-200 and my 2x. I totally failed in that respect due to the fact I was manually focusing on a plane moving at silly speeds but I did fire off a few test shots afterwards. They looked OK, not great but certainly useable. I'll have a look and see if I can find them.

Harry.
 
There's no point getting a 2x converter on an f4 lens if you want to use autofocus, to do that you'd need an f2.8 lens. The 70D sensor is 20 megapixels so you may be able to crop to get the frame you want without another extender using the 1.4x.
 
Thanks, Harry. Though because of how the combination works re AF etc, I'm not now inclined to go this route but to take onboard the good advice of fellow TP'ers - It would be too much of a compromise.

I would rather stay with and learn what I have already and perhaps think again this time next year about my needs, if any. I have a Canon 100mm f2.8L IS Macro to master as well once the mini-beasts are on the prowl again in the Spring. And a Sony RX100 II.
 
drounding said:
There's no point getting a 2x converter on an f4 lens if you want to use autofocus, to do that you'd need an f2.8 lens. The 70D sensor is 20 megapixels so you may be able to crop to get the frame you want without another extender using the 1.4x.
Click to expand...

....Yes, I have noticed that at ISO 400 and in good light, I can crop more than I expected to on the 70D. It may be only a **D as opposed to a *D but it is latest state of the art and a very good machine overall and I don't even shoot video. It's fully articulated touch screen ain't no gimmick - It's excellent for quickly changing settings and easier than some of the smaller top buttons.

Coming from old school SLR and also being a graphic designer I always try and compose every shot in camera if I can but that gets trickier on fast moving winged creatures!
 
Hi Robin good decision to stick with the 1.4
I've got the 1.4 and 2x extentions to use with my 300 2.8 as already said I think it would be tricky with an f4 lens
I find the 1.4 one excellent and can't see any difference in IQ with it on
The 2x is still excellent but I find it tricky to use I need good light but it may be just my hands arnt steady enough but have started to use a monopod
 
LCPete said:
Hi Robin good decision to stick with the 1.4
I've got the 1.4 and 2x extentions to use with my 300 2.8 as already said I think it would be tricky with an f4 lens

I find the 1.4 one excellent and can't see any difference in IQ with it on

The 2x is still excellent but I find it tricky to use I need good light but it may be just my hands arnt steady enough but have started to use a monopod
Click to expand...

....Hi Pete, I can't see any IQ difference so far with the Canon 1.4x on/off either. I expected to but it's not there to the naked eye. My 1.4x is a MkIII which is reputed to be the best one.

Re monopod, I have a Manfrotto MVM500A monopod with the fancy fluid cartridge mini legged base. I haven't used it fully yet but it's very fluid in all its movements and very sturdy, but too heavy for miles of walking. I'm lucky in that my 'Backyard' has 5 species of Dragonflies and many other mini-beasts and it's all very close to my back garden.

What I want to ask though is whether to switch off IS for a monopod - I know it's considered best practice for tripods. Photogs might point out that IS lenses like my 70-200 f4L and 100 f2.8L Macro don't need a 'pod but with such a shallow DoF on the Macro you need all the help you can get. Perhaps this is a subject for a new thread.
 
RedRobin said:
...

However, Canon's EF Lenses brochure PDF does list both Canon 1.4x and 2x Extenders as being accessories for the Canon 70-200mm f4L IS and without any AF restrictive note.

.
Click to expand...

This is because some Canon bodies do not loose autofocus when going over the F5.6 max aperture.
 
RedRobin said:
What I want to ask though is whether to switch off IS for a monopod .
Click to expand...

With long lenses I always keep IS on if my hand is going to be on the camera when the shot it taken. That means it's always on when handheld or on a monopod and it's always on when used on a tripod without a remote release.
 
Yes the newer canon IS can detect when they are on a tripod and certainly I use is with a monopod
You are lucky having dragonflies in your backyard
My extenders are the mk 3 versions
The 100L is a fantastic lens BTW can use it handheld it great for damselflies as I find damsels are long gone by the time I've set up a tripod the is means you don't have to use high ISO
 
There are a few options to use 2x on this lens with a crop Camera and still retain AF (without taping the pins) :-
#1 Use live view AF (this is not restricted to f5.6 but is slower than normal phase AF)
#2 Use stacked 1.4x tc's (Could be one Canon and one third party like Kenko Pro - the Camera will only see one tc so will attempt to AF)
#3 use a non reporting tc.

Not that I would advocate any of these methods with this lens as you would lose too much IQ (it is very good with just a 1.4x tc though).
 
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hollis_f said:
The problem would arise when trying to focus. All lenses are wide-open when AutoFocus is in operation, because AF performance is better with more light. One reason why people like fast lenses (with wide apertures) is that they grab more light when wide-open, allowing for better AutoFocus.

Your 70-200 without a TC is f4 - and the AF should be impressively fast. With the 1.4x TC it becomes f5.6 (the amount of light reaching the AF sensor is halved). You'll probably notice the AF is a little slower - especially if the light levels are fairly low.

With a 2x TC your lens becomes a 140-400mm f8. The amount of light reaching the AF sensor is 4 times less than without a TC. Indeed, the amount of light is so low that Canon have decided that most of their cameras won't even try to AF if the maximum aperture is smaller than f5.6 - most of the time it's just not worth it even trying.

You can attempt to fool the camera - tape pins on the TC or use a different TC that lies to the camera. But none of them solve the basic problem - you can't AF properly with insufficient light.
Click to expand...

This is not quite right. Though good light obviously helps, the main problem with AF at higher f/numbers is the effective physical diameter of the aperture is reduced. Phase-detect AF works by comparing images seen through either side of the lens. Reducing the aperture beyond a certain point means there's not enough difference between the two sides for an accurate result.

Phase-detect AF actually works well in quite low light, if you give it a decently contrasty target to lock on to.
 
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