Sponsor Message:
Aviation Photography Forum
My Starred Topics | Profile | New Topic | Forum Index | Help | Search 
70-300 Is USM With Teleconvertor Help Please  
User currently offlineHarryImp From UK - England, joined Jun 2011, 55 posts, RR: 0
Posted (3 years 5 months 1 week 18 hours ago) and read 7351 times:

Hi all

I have got a 70-300 IS USM f/4-5.6 but fancy a bit more reach. I thought a 1.4X TC was out of the equation because I lose AF. However I was speaking to someone to day who showed me had a 75-300 III USM with a Kennko 1.4X teleconvertor and the AF was totally unaffected??

So would i be able to use a TC or not???


Harry

16 replies: All unread, jump to last
 
User currently offlineLGW340 From United Kingdom, joined May 2007, 317 posts, RR: 0
Reply 1, posted (3 years 5 months 1 week 18 hours ago) and read 7345 times:

You can use a Kenko tele converter which will be fine for reading regs etc but will not be good enough for uploads here. The Canon EF 1.4x and 2x will not fit the 70-300 IS.


Live life from the window seat...
User currently offlineHarryImp From UK - England, joined Jun 2011, 55 posts, RR: 0
Reply 2, posted (3 years 5 months 1 week 17 hours ago) and read 7345 times:

Will the AF still work???


May I ask why it wont be good enough for uploads on here??


User currently offlineothic From Sweden, joined Jun 2007, 171 posts, RR: 0
Reply 3, posted (3 years 5 months 1 week 17 hours ago) and read 7338 times:

AF will NOT work

/othic



A boy learn's much more at the airport then he do at school
User currently offlineHarryImp From UK - England, joined Jun 2011, 55 posts, RR: 0
Reply 4, posted (3 years 5 months 1 week 17 hours ago) and read 7337 times:

Hmm ok... well how come this bloke with a 75-300 III USM managed too? I thought the same as you but it baffled me!!

Harry


User currently offlinelegoguy From United Kingdom, joined Jun 2006, 3314 posts, RR: 39
Reply 5, posted (3 years 5 months 1 week 14 hours ago) and read 7295 times:

Depending on which Kenko 1.4x converter it is, autofocus may work. I believe the older converter will allow the camera to attempt to autofocus, but half the time may not work unless the conditions are quite bright and contrasty, i.e nice bright sunlight.

I have had two Kenko teleconverters, both 1.4x. The older version allowed autofocusing whilst from memory the newer version (PRO 300) did not. As with any teleconverter, taping up several connecting pins allows the camera to try autofocusing but the accuracy of the focusing may not be 100% and this method it not really recommended. I think I read that it can perhaps burn out the autofocus motor in the lens.

As LGW340, the Canon 1.4x and 2x extender's do not physically fit on the Canon 70-300mm IS USM, they only fit on L range lenses. Kenko teleconveter do however fit, but the results can be iffy. From the resulting images, you might get one or two good shots as the 70-300mm is a good lens, but the majority will not be the best of quality.

I hope this helps a bit,

Dave



Can you say 'Beer Can' without sounding like a Jamaican saying 'Bacon'?
User currently offlineckw From UK - England, joined Aug 2010, 769 posts, RR: 16
Reply 6, posted (3 years 5 months 1 week 9 hours ago) and read 7261 times:

With Canon convertors, there is a pin which communicates with the lens to determine the effective aperture. On non-pro cameras, Canon has decided that accurate auto-focus cannot be acheived at apertures smaller than f5.6, hence they have built in an autofocus limiter.

3rd party manufacturers do not normally incorporate this extra pin, hence the camera will not be limited in attempting to autofocus.

The problem is that the autofocus process is not a simple on/off - it depends on light and contrast. In some situations (good light and contrast) the 300 f4-f5.6 will work fine with a convertor, in others it won't.

Its a bit like limiting the top speed of certain cars - they CAN go faster, but certain components (usually the tires) cannot guarantee the necessary level of safety beyond a certain speed. Go beyond that speed in a straight line, you're probably ok - start cornering hard and you're in trouble.

Cheers,

Colin



Colin K. Work, Pixstel
User currently offlinevikkyvik From United States of America, joined Jul 2003, 10349 posts, RR: 26
Reply 7, posted (3 years 5 months 1 week 9 hours ago) and read 7258 times:

Quoting ckw (Reply 6):
Canon has decided that accurate auto-focus cannot be acheived at apertures smaller than f5.6, hence they have built in an autofocus limiter.

Is that with a lens + TC?

Just curious, as I use my F3.5 18-55 lens all the time with my 1000D (no TC, obviously).



How can I be an admiral without my cap??!
User currently offlineLGW340 From United Kingdom, joined May 2007, 317 posts, RR: 0
Reply 8, posted (3 years 5 months 1 week 1 hour ago) and read 7237 times:

The lens WILL AF with the converter.


Live life from the window seat...
User currently offlineHarryImp From UK - England, joined Jun 2011, 55 posts, RR: 0
Reply 9, posted (3 years 5 months 1 week 1 hour ago) and read 7232 times:

Ok thanks


So it will work?? Or not all the time?? Which Kenko convertor will I want?

What difference will it make to the quality of the picture??? I want good pictures, but i dont think will ever be up to Airliners standard for a while yet anyway. So i am just concentrating it for my own benefit atm. Wht visual changes will i see??


Harry






Harry


User currently onlineeggohoek From Hungary, joined Nov 2005, 55 posts, RR: 1
Reply 10, posted (3 years 5 months 6 days 21 hours ago) and read 7212 times:
AIRLINERS.NET CREW
PHOTO SCREENER

If you stick down the last 3 detectors of Kenko TC you get AF. But you get very bad picture quality if you use Canon 70-300 IS with TC. If you need extra focal length better choice to buy a lens with 400 mm focal length.

TC's made first of all to prime lenses, but you can use TC with Canon 70-200 L series (1,4x will better like 2x).
I tried 70-200 f4 L IS with Kenko 1,4x and that combo gives better quality like 70-300 IS. But the better choice if you don't use TC with zoom lens (buy a zoom with 400mm).


User currently offlinetrvyyz From Canada, joined Oct 2004, 1375 posts, RR: 10
Reply 11, posted (3 years 5 months 6 days 18 hours ago) and read 7202 times:

I had used this lens with a tamron 1.4x convertor in the past. it does autofocus, but hunted crazily, so annoying that you feel to opt for MF instead. The picture quality will not be that great anyways.

User currently offlineckw From UK - England, joined Aug 2010, 769 posts, RR: 16
Reply 12, posted (3 years 5 months 6 days 9 hours ago) and read 7170 times:

Quoting vikkyvik (Reply 7):
Quoting ckw (Reply 6):
Canon has decided that accurate auto-focus cannot be acheived at apertures smaller than f5.6, hence they have built in an autofocus limiter.

Is that with a lens + TC?

Just curious, as I use my F3.5 18-55 lens all the time with my 1000D (no TC, obviously).

Sorry, sometimes this gets confusing. The smalller the NUMBER the larger the APERTURE - so 3.5 is a larger aperture than 5.6, f16 is a smaller aperture than f8 - by smaller and larger I'm refering to the diameter of the iris, which determines the amount of light reaching the AF mechanism.

Canon has set aribratry limits on AF - any aperture smaller than f5.6 (f8, f11, f16 etc) will not focus on a non-pro camera. Pro cameras can still AF at f8

Quoting HarryImp (Reply 9):
So it will work?? Or not all the time?? Which Kenko convertor will I want?

What difference will it make to the quality of the picture??? I want good pictures, but i dont think will ever be up to Airliners standard for a while yet anyway. So i am just concentrating it for my own benefit atm. Wht visual changes will i see??


Yes, it will work. Sometimes. And it may be slow and hunt a lot.

In terms of quality, you will see less sharpness and contrast. I'm afraid you can't have a definitive answer to this - what is acceptable in terms in image quality is a personal thing,

Cheers,

Colin



Colin K. Work, Pixstel
User currently offlinevikkyvik From United States of America, joined Jul 2003, 10349 posts, RR: 26
Reply 13, posted (3 years 5 months 5 days 12 hours ago) and read 7118 times:

Quoting ckw (Reply 12):

Ah sorry that was my mistake. However my real question was whether you were referring to lens + TC specifically. Hard to imagine that Canon consumer cameras won't focus at F8. I use my camera out to F16 and beyond with AF all the time!



How can I be an admiral without my cap??!
User currently offlineMcG1967 From UK - Scotland, joined Apr 2006, 517 posts, RR: 1
Reply 14, posted (3 years 5 months 5 days 12 hours ago) and read 7114 times:

Quoting vikkyvik (Reply 13):
However my real question was whether you were referring to lens + TC specifically. Hard to imagine that Canon consumer cameras won't focus at F8

If you are using a Canon 400mm F5.6L, and you add a 1.4xTC to it, then the largest aperture with this combo of lens & TC becomes F8. The only Canons that will Autofocus with this combo at an F8 aperture is a pro camera.

If you are using a Canon 300mm F4L IS and you add a 1.4xTC to it, then the largest aperture with this combo of lens & TC becomes F5.6. The Canon consumer range should autofucus with this combo at an aperture of F5.6.


User currently offlineckw From UK - England, joined Aug 2010, 769 posts, RR: 16
Reply 15, posted (3 years 5 months 5 days 10 hours ago) and read 7108 times:

Quoting vikkyvik (Reply 13):
Ah sorry that was my mistake. However my real question was whether you were referring to lens + TC specifically. Hard to imagine that Canon consumer cameras won't focus at F8. I use my camera out to F16 and beyond with AF all the time!

Bit of confusion here - what we are talking about is the maximum aperture of the lens. Regardless of which aperture you set, autofocus is performed with the lens wide open - it only shuts down to the your selected aperture at the moment of exposure.

Canon (and indeed ALL AF cameras) require a certain amount of light (or strictly speaking contrast) to accurately focus. The key figure is the f stop of the lens wide open. If you add a 2x convertor, this figure is reduced by 2 stops (an f4 lens becomes an f8) , by 1 stop for a 1.4 convertor.

Cheers,

Colin



Colin K. Work, Pixstel
User currently offlinevikkyvik From United States of America, joined Jul 2003, 10349 posts, RR: 26
Reply 16, posted (3 years 5 months 5 days 8 hours ago) and read 7104 times:

Quoting McG1967 (Reply 14):
Quoting ckw (Reply 15):

Ohhh, OK, I am vastly less confused now  

I did know about cameras focusing at the widest possible aperture, but it didn't register that that would change with a TC (probably since I've never used a TC).

Thanks again.



How can I be an admiral without my cap??!
Top Of Page
Forum Index

This topic is archived and can not be replied to any more.

Printer friendly format

Similar topics:More similar topics...
Sigma 70-300 Or Tokina 80-400? Help Please posted Sun Dec 11 2005 21:51:27 by MH017
300 L Is USM F4.0 Modes/ Urgent Help Please posted Wed Jul 6 2005 00:30:41 by LHRSIMON
Need Help On Canon 70-300mm F/4-5.6 Is USM! posted Wed Dec 19 2007 03:42:04 by Mnazarinia
70-300mm F/4-5.6 Is USM Or L Glass posted Thu Jan 3 2008 12:50:43 by Rsmith6621a
Canon 70-300 Is Lens, Is It Worth The Price? posted Fri Dec 28 2007 20:46:27 by MIAMIx707
Is My Lens Not In Order (EF 70-300 IS)? posted Thu Jul 13 2006 17:01:53 by Aero145
Canon EF 70-300mm F/4-5.6 Is USM Review Wanted posted Thu Apr 6 2006 12:01:46 by Deaphen
Is This Photo Bad? Help Please? posted Tue Jan 17 2006 15:20:09 by Devil505x
New Canon EF 70-300mm F/4-5.6 Is USM posted Wed Oct 19 2005 00:12:17 by TRVYYZ
Canon 28-300 Is USM Vs. 100-400 Is USM posted Wed Sep 28 2005 19:16:27 by Stefan