New to teleconvertors - can you give a quick guide?

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#1
well, or an easy answer.... I'm thinking about heading to Bempton for a few days next year for Puffins - I have a canon f4 is 70-200mm lens but i think it's not going to be enough for the job - would be make better sense to hire a longer zoom - or hire/purchase 2nd hand a teleconvertor - i am reading about them and they could lead to decrease in image quality or be a bit of a job to get used to which makes me think hiring a longer zoom would be better, but wondered what the lovely people of the forum think? I've never shot birds or wild animals before so its going to be an interesting few days (if it happens) as i don't think I'll do a workshop or anything - but i guess i might still change my mind on that. I'm thinking waaay ahead here but just trying to book something in to look forward to ( I priced up a trip to east iceland for puffins and in making the trip worth getting over there, so stopping in the north a bit too, it ended up a taaaaaaaaaaaad crazy for a solo trip - there's a reason i always visit there out of season lol!) obv the teleconvertor would be the cheaper way to get more reach, than the lens hire.

thanks :)
 
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AndrewFlannigan

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#2
Modern teleconverters are much better than their predecessors in the 1980s. On the other hand all teleconverters have a major problem regardless of how good they are optically. As you extend the focal length you reduce the maximum aperture. Thus a 1.4x converter will drop your f4 to f5.6 and a 2x converter will drop it to f8. This means you'll be dropping your shutter speed or increasing your ISO AND you'll be reducing the efficiency of your autofocus. Whether this is acceptable will depend on the body you're using because the better the image quality at high ISO and the more sensitive the autofocus system the less of a problem these changes will be.
 
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#3
First thing to do is find out if your camera will AF at f8, if it wont you that rules out a 2* TC on your lens.
Your 70-200 takes a 1.4 TC very well ,it will AF and IQ is not bad ( I used to have that combo on a 7D) but it will still be a bit short.
Your best and probably cheapest option is to hire one (http://www.lensesforhire.co.uk/search ) unless you want to spend silly money I would get the Canon 400mm f5.6 or one of the big Sigmas at £60 odd for 3 days its a no brainer
 

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#4
Do you currently shoot full frame or 1.6x crop? If full frame, you might consider a mid level crop body so you get the extra (apparent) reach and keep the f/4 aperture's shutter speeds/ISOs.

While modern telecons are better than older ones, adding extra elements won't improve image quality and will (as Andrew pointed out) cost you a stop (or 2) of available aperture. Depending on the amount of use a longer lens is likely to get, maybe a relatively cheap 70-300 could be the answer. Not perfect but a second hand example shouldn't be too expensive and could be resold at a minimal loss should it prove to not be the answer!
(Back in the old days [when real camera shops still existed], you could probably have borrowed a potentially suitable lens for a few days or maybe rented it and used the rental as a deposit against it should you decide to buy. You MIGHT be lucky enough to still have such a shop [and a relationship with them that would allow such a deal] locally.)
 
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#5
My 150-600 Sig sport rarely comes off one of my bodies but I do use the Siggy converter on occasions, they are NOTHING like the old ones as said above, and depending on the camera you have you may as I do retain AF

It is something I have, rarely use but would not be without !!!
 
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#6
Understand that using a teleconverter is just another form of cropping... it doesn't make much difference if you crop in post, use a crop sensor, or magnify the image circle (using a TC) to accomplish the crop. Each option is going to result in very similar IQ, with the same light/area and DOF in the final image. Each method is likely to result in a different MP image, but that's not likely to be the limiting factor. Generally, as long as you have enough pixels remaining it is best (or just as well) to just crop the image in post.

Adding a TC is quite possibly the worst option with an F/4 zoom lens... it will reduce sharpness and the lens isn't at max sharpness wide open anyway, and it will add/exacerbate issues like CA. Plus you will probably also loose some AF functionality/accuracy, especially in lower light (it may be nearly unusable with a 2x depending on the camera).

Using a longer lens is also just another form of cropping (magnifying the scene/image circle). But if you can use a longer lens that is also better/faster there is usually a notable benefit (and high cost).
 
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#7
Often it is faster just to change to crop mode in my Nikon than add the converter
 
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#8
I don't think an f4 70-200 will leave you satisfied at Bempton, I would opt for a longer lens ... 150-600 would be fine.
 
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#9
Often it is faster just to change to crop mode in my Nikon than add the converter
On some cameras using crop mode has the benefit of increasing the max FPS with smaller file sizes... it can be a worthwhile consideration.
Otherwise you're probably better off cropping in post, if nothing else for the increased flexibility in composition it provides.
 
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#11
Thank you all - this is very useful.

I have a 5Dii that i use with a 24-70 f.28 and 70-200 f4 - i still have a 40d but i don't tend to take that out with me, i use it more as a back up if i shoot a music gig and keep an 85mm prime lens on it (cos its a nice lens more than anything! as well as a little bit extra reach)

it sounds like renting a longer lens is going to be the best bet for if/when i go - i thought it probably would be but wondered if a teleconvertor might be a more cost effective than renting but wasn't sure if it was too big of a trade off. I've never used a lens as long as 600 @gramps - if i go for that, as im so small it might tip me off the cliff lol! Would i need some kind of stand if using that length lens? I have rented before so i'm cool with that.
 
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#12
Would i need some kind of stand if using that length lens? I have rented before so i'm cool with that.
Many can hand-hold the Tamron or the Sigma 'C' ('S' - Sport is much heavier) but if you doubt your ability to hold it then a monopod would work well to take the weight.
 
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#14
Thank you all - this is very useful.

I have a 5Dii that i use with a 24-70 f.28 and 70-200 f4 - i still have a 40d but i don't tend to take that out with me, i use it more as a back up if i shoot a music gig and keep an 85mm prime lens on it (cos its a nice lens more than anything! as well as a little bit extra reach)

it sounds like renting a longer lens is going to be the best bet for if/when i go - i thought it probably would be but wondered if a teleconvertor might be a more cost effective than renting but wasn't sure if it was too big of a trade off. I've never used a lens as long as 600 @gramps - if i go for that, as im so small it might tip me off the cliff lol! Would i need some kind of stand if using that length lens? I have rented before so i'm cool with that.

I do rent, occasionally, (in fact you don't think all those photographers you see at sports own them :) ), but I still use a converter on occasion
 
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#15
Adding a TC is quite possibly the worst option with an F/4 zoom lens... it will reduce sharpness and the lens isn't at max sharpness wide open anyway, and it will add/exacerbate issues like CA. Plus you will probably also loose some AF functionality/accuracy, especially in lower light (it may be nearly unusable with a 2x depending on the camera).
.

:(

Well that lets my Siggy 150-600 sport out then :) :)

As for support, I use a Gitzo and Wimberley with the Siggy sport, but have hand held, ................ heavy
 
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#17
Works fine on my D4s/D5
 
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#18
Works fine on my D4s/D5
"Fine" is highly subjective...with enough light and a high contrast subject my D5 will AF with an f/11 lens (center point only). At f/8 you are severely limited on AF points with the D4s/D5. On the D5 you only have 15 AF points fully functional (down from 153), with only the center point functioning as a dual line/cross type (down from 99).
Beyond f/8 those relatively few remaining focus points become vignetted/masked by the aperture blades and become more and more ineffective.

I've used the Sigma 600 lenses (I currently own the 60-600), even just stepping over the f/5.6 point (i.e. f/6.3) affects them notably in demanding situations (lower light/contrast, faster/more erratic subjects). I won't put a TC on one...
 
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#20
At the long end where the lens is f/6.3, even just a 1.4x TC will make it an f/9 lens... no camera is rated for PDAF with a max aperture smaller than f/8. At best it will be unreliable...
Sigma cheat in the firmware it works as f8.5... makes it think it’s f8 works fine.. I used a canon 1.4tc most of the time with a sigma 150-600mm taking it to 840. Even retained all the af points. In fact most of my Flickr photos have tc’s Attached weather it the canon 1.4 or 2x now have the m3 version for improved firmware, improved af. The lenses used are either sigma 150-600, or canon 400mm f4 DO, the all canon set up works well for birds in flight, the sigma struggled.
 
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#21
Sigma cheat in the firmware it works as f8.5... makes it think it’s f8 works fine.. I used a canon 1.4tc most of the time with a sigma 150-600mm taking it to 840. Even retained all the af points. In fact most of Flickr photos have tc’s Attached weather it the canon 1.4 or 2x now have the m3 version for improved firmware, improved af. The lenses used are either sigma 150-600, or canon 400mm f4 DO
Canons actually disable AF points at the aperture steps don't they? Current Nikons don't... you can select any of them and it will try to use it even if it's pointless.

It doesn't matter if the lens lies/the camera allows you to select/use an AF point. What matters is if the PDAF system can actually see the portion of the objective lens where the PDAF images are taken from. These images are then compared for position (phase) by the AF sensor lines.

I made this over simplified drawing to help explain it.
PDAF_.jpg

The f/8 images come from the more central area f/8 area of the objective lens. Because of this they have much less angular difference which makes them faster but less accurate (contributes to increased hunting and misfocus). Only a few cameras have AF systems that use images taken from the f/2.8 objective area, those focus points will be the slowest but also the most accurate.
You can't go much tighter than the f/8 area because you need at least two separate images to compare, and when they get to close together there's not enough angular difference for there to be a phase offset when not in focus. I.e. there are no f/11 rated AF points and there probably never will be.

If the sensor cannot get the images it needs, due to the lens' aperture blocking that area of the objective element, then those focus points are physically disabled... that's why cross points revert to line type.

It's probably worth noting that there is all of the light required for a complete image at every point on the objective element... i.e. a lens can have any size objective element, that only limits the lens' max aperture. And increasing aperture in order to increase exposure is essentially just stacking more images(light) onto the sensor. I.e. the images being compared for PDAF phase are the same image/scene, just taken from a different location and of less light.
And it's also worth noting that it is the size of the area of the objective element used to take these individual images from that determines the amount of light the PDAF sensor receives (labeled as virtual apertures in the diagram). The lens' aperture cannot pass any more light to the AF module than that equivalent aperture restriction. I.e. faster lenses do not pass more light to the PDAF module.
 
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#22
Canons actually disable AF points at the aperture steps don't they? Current Nikons don't... you can select any of them and it will try to use it even if it's pointless.
.
They do depending on the body.. one thing to point out also depends on the lens. The sigma at f8 worked all points. that's with the Canon 1.4 tc assuming the sigma tele does the same.

Canon 400mm f4 DO plus Canon mk2 2x TC it limted to single point or 4 point AF
Canon 400mm f4 DO plus Canon MK3 2x TC it had full AF available to it. So you see updated electronics improve the AF selection, I use 9 point for bird in flight and motorsport.

Haven't tried the 1.4 and 2x Tc's stacked to make it f11 to test. (too dark to try to night now)

Thats why I say its firmware hack

I use a Canon 1Dx MK2 body and can only talk about that.
 
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#24
So you see updated electronics improve the AF selection, I use 9 point for bird in flight and motorsport.
You missed the point of that whole post...
The ability to see the objective lens areas in order to get the images PDAF requires is a real/physical limitation. There is no way of getting around it. Firmware and whether the camera lets you select points or not is entirely irrelevant. It's like the trick of taping over the contacts so the camera doesn't know a TC is being used... doesn't improve the functionality in any way other than letting you do something you shouldn't.
 
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#25
I'll throw a curve ball in: spend your money on a few days at Skomer or Skokholm instead - no need for a long telephoto - this was taken on my phone :D

Skomer Puffins
View: https://flic.kr/p/cv1JfA
I agree Brampton isn’t the place I would head to for Puffins. If you can get booked on an overnight stay on Skomer/Skokholm you would get better chances at shorter focal lengths.
 
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#26
"Fine" is highly subjective...with enough light and a high contrast subject my D5 will AF with an f/11 lens (center point only). At f/8 you are severely limited on AF points with the D4s/D5. On the D5 you only have 15 AF points fully functional (down from 153), with only the center point functioning as a dual line/cross type (down from 99).
.

.

Well I have been shooting sports photography for Classic Cars magazine for a number of years and for years before that and now I have only ever used one focus point, old school
 
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#27
You missed the point of that whole post...
The ability to see the objective lens areas in order to get the images PDAF requires is a real/physical limitation. There is no way of getting around it. Firmware and whether the camera lets you select points or not is entirely irrelevant. It's like the trick of taping over the contacts so the camera doesn't know a TC is being used... doesn't improve the functionality in any way other than letting you do something you shouldn't.

True taping the contacts to trick it, is different. But the 1dx mk2 must be able to see all the points to be able to select. The mk2 2x extender couldn’t see them all. Don’t forget from what I know Nikon have more points then Canon do.
The canon mk3 extender has 9 elements where there mk2 had 7. So I assume the firmware tells the body it can see more of the focusing system on the canon.

Like I say I don’t know much about the Nikon.

But birds in flight 9point square af selection works well for birds in flight and motorsport.

Canon flag ship af is 90 something point af, not 150 like someone mentioned about Nikon.
 
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#28
The canon mk3 extender has 9 elements where there mk2 had 7. So I assume the firmware tells the body it can see more of the focusing system on the canon.
For the 1DX Mk2 (with certain lenses and Mk3 TC's) Canon has remapped all of the focus points to the f/8 image area sensors...
But that doesn't change the fact that it's physically impossible for an f/2.8 or f/5.6 AF point to be fully functional at f/8. Nor that f/8 autofocus points are not as accurate as f/2.8-f/5.6 autofocus points are... if they were, all focus points in all cameras would be f/8 and there would be no restrictions to using wider apertures.
 
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#29
For the 1DX Mk2 (with certain lenses and Mk3 TC's) Canon has remapped all of the focus points to the f/8 image area sensors...
But that doesn't change the fact that it's physically impossible for an f/2.8 or f/5.6 AF point to be fully functional at f/8. Nor that f/8 autofocus points are not as accurate as f/2.8-f/5.6 autofocus points are... if they were, all focus points in all cameras would be f/8 and there would be no restrictions to using wider apertures.

Well I am told by the 7d owners they have the same system.
But if Canon are mapping the full system on the 1dx mk2 to be f8 then I am pretty sure the system can see them. Why you can focus with the widest of them the highest and lowest.

Maybe there all f2.8 on the canon flagship model. Lol

Can only tell my experience of owning the f2.8 70-200 focus is no better or faster then my F4 DO even now running a mk3 2x tc, there’s no noticeable drop of in speed of tracking. But I do tend to use the center 9 that are definitely f2.8.

But there’s more impressive improvements in the canon mk3 to mk2 tc it’s brighter and clearer and sharper.
Plus the printable file size is larger your actually sharper using the 2x tc then cropping for print. For simple web browsing you can get away with simply being crop king right down 800pix on the longest side.

So the use of modern tc’s depneds what you want really.

I use them without fear as there’s not much in it for web anymore, but as I print the tc is invaluable.

As for all body’s doing the same well you get what you pay for but the 7d is impressive for its price point.

Biggest thing with tcs imho is to calibrate the tc to the body, having used 3 on 3 lenses they altered the micro focus massively 2 back focus by 3, (1.4tc) or 10 steps, (mk3 2x tc) the 3rd front focuses by 3 steps.(mk2 2x tc) Adjusting that, sharpens them all up to close to no different (the mk3 2x tc print is the sharper, noticeable). Biggest thing is light levels drop. I have test images all at f8 couldn’t tell what was what really full stop, except the for mk2 2x tc which was noticeable softer then the mk3 version.

Not saying my 400mm do will out perform a 600mm prime though, but it does out perform the sigma 150-600mm.

Oh from reports the 70-200mm F4 is sharpen enough to handle tc’s back early in my career remember people saying no noticeable drop off in the mk2 1.4 tc, now is push and say the same about the mk3 2x tc.
 
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#30
But I do tend to use the center 9 that are definitely f2.8.
They are only f/2.8 if you have a lens that is at f/2.8 or wider during autofocus; in that case those points are actually f/2.8+f/5.6+f/8 simultaneously... this is what makes PDAF faster and more accurate with faster lenses. In this case you have a minimum of 3 pairs of images being compared for focus (phase position).

When a lens is slower than f/2.8 those sensors are unusable, because the images they require are unavailable, and the points then become f/5.6+f/8... A lot of cameras use a horizontal f/5.6 line sensor combined with a vertical f/8 sensor, which functions as an f/5.6 cross type sensor. And then when the f/5.6 image areas becomes blocked by the aperture blades the cross point reverts to an f/8 line type, because the f/8 images are all that remain.
 
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#31
They are only f/2.8 if you have a lens that is at f/2.8 or wider during autofocus; in that case those points are actually f/2.8+f/5.6+f/8 simultaneously... this is what makes PDAF faster and more accurate with faster lenses. In this case you have a minimum of 3 pairs of images being compared for focus (phase position).

When a lens is slower than f/2.8 those sensors are unusable, because the images they require are unavailable, and the points then become f/5.6+f/8... A lot of cameras use a horizontal f/5.6 line sensor combined with a vertical f/8 sensor, which functions as an f/5.6 cross type sensor. And then when the f/5.6 image areas becomes blocked by the aperture blades the cross point reverts to an f/8 line type, because the f/8 images are all that remain.
Read all that when I was looking to get the 1d mk3 when it come out. But things must have moved on a tad, as the Sigma 150-600 does auto focus with a 1.4 tc even sold with one as a kit by sigma, despite being f9, I used to to stop it to f10 for sharpness. So Sigma must have used a firmware hack/trick?

But from I what I can find out the 1Dx MK2 canon might not have as many total AF points it has more F2.8 points, and it has 21 cross type sensors at f8! :) Seen where all the cross type are now on the canon and 3x3 box are all cross types even at f8, but all 61points at still active at f8, on the 1dx mk2, and sorry to the 7D boys its not quite the same AF system similar but not the same not quite as many cross types, from what I have been able to find out.
 
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#32
Apertures and FL aren't usually 100% accurate, they are usually rounded (to whatever sounds better). But if the camera will let you select a focus point, it will then try to use it even if it's degraded/unusable... f/9 is only 1/3 stop beyond f/8; the images are probably just slightly degraded/vignetted (Sigma does note that the combination f/6.3(f/9) FL's require good light/contrast.
The aperture you have the lens set for makes no difference here; the lens doesn't stop down to the setting until the mirror goes up after focusing.
 
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#33
@davekiddle @rob-nikon i am too wary of the boat trips being affected by weather to go for a trip to skomer - travelling from essex, it feels like too much of a risk to get all the way over there, probably have to stay the night before and after and then risk having no trip to the island at all due to weather. i imagine a summer like we've just had could have been a real nightmare from that perspective. that was my original plan, but i feel like i just can't justify the spend/risk. i havnt made final decision but investigating Bempton has been my train of thought at the moment. i had originally planned to do a work shop so take the stress out of getting a boat ticket/accommodation but the prices of those keep going up which added to my uncertainty/nervousness about the risk of boat cancellation. I'm not very good at decisions..... :confused:
 
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