Tele Converters and image quality loss

[thedude]

Hello everyone!

I've posted several questions regarding low light, fast lenses. After reading the many high quality responses, I'm now considering two lenses:

1)Canon 70-200 f2.8L (no IS)
2)Sigma 70-200 f2.8

Currently, I'm using a Canon 75-300 f4-5.6 USM to take HS football shots. As you can imagine, the lens is completely not up to the job as the the night progresses. I believe that the two lenses listed above should fix most of my problems with light, however, I'm afraid that I may miss the extra 100mm on the long end.

Enter the 1.4 TC's

Both Canon and Sigma offer 1.4 and 2.0 TC's that work with the lenses listed above in AF mode.

Are there any other factors to consider (beside losing 1 stop with the 1.4 and 2 with the 2.0)

How much is the image quality degraded using a TC?

I'm leaning toward the Sigma strictly because I can buy it and a 1.4 TC for ~$850 versus the Canon's price of ~$1250
Does anyone know of two images shot with both lenses for comparison sake?

Thanks in advance!

[drisley]

I can only speak for the Canon EF 1.4x Extender.
In my experience, there is absolutely NO quality loss!
See my review here
http://photography-on-the.net/forum/showthread.php?t=40700

Some say there is a small quality loss with the 1.4x extender, however, I've done side by side tests and blown them up to 200% and I see absolutely no difference. The 1.4x extender is definately a great buy.

The 2x extender is supposed to show visible quality loss. I have no experience with it, so I cant say for sure. I would like to do some tests myself.

As far as lenses go, if you have the money, get the canon over the sigma.
The sigma is supposed to be excellent, but I've seen a few people here who end up selling their's for the Canon equivalent (I've also seen some sell their sigma 70-200 F2.8 for the Canon F4 version).
Yes, the sigma is a tremendous lens, but for some people it leaves them wanting more. THis is just what I've seen and read, no personal experience.

[DocFrankenstein]

I have yet to handle a converter of any sort, but I've heard that you'd want to be using same brand lens/converter combo.

Some complained that it works better, because diff brand combination gives you fringing and other special effects. Again, I have no converter and it's what I read.

[Tapeman]

I have both the Canon 1.4x mkII and 2x mkII converters.

I use them both with the 70-200 2.8L a lot.

The image quality with both converters is excellent.

I even have stacked the converters, but then the image quality suffers.

Bottom line: on good glass they add a lot of versatility for the buck.

[Cadwell]

I have yet to handle a converter of any sort, but I've heard that you'd want to be using same brand lens/converter combo.

Some complained that it works better, because diff brand combination gives you fringing and other special effects. Again, I have no converter and it's what I read.

Not true in my experience. I have a Sigma 1.4x which works flawlessly on both my Sigma EXs and Canon Ls.

[Cadwell]

Oh, I should also add that I have both the Canon and Sigma 2x TCs and neither works very well on anything. I very rarely use either.

[thedude]

Interesting comments...

To answer the comment about going with Canon. Obviously! However, I am having problems swinging even the purchase price of the Sigma. There's a pretty large difference between the two price-wise. According to many reviews however, there isn't a substantial performance difference between them, making the sigma a great value.

I had assumed that if I bought sigma, I would buy the sigma TC for compatability sack and vice versa with the canon.

Thanks for the link to the review drisley!

I went to the Houston Texans preseason game last night and found myself watching the photographers on the sidelines. I couldn't help but wonder what they were all carrying! LOL I have no clue what they had other than the lenses were HUGE!

[dn7elson]

Are there any other factors to consider (beside losing 1 stop with the 1.4 and 2 with the 2.0)

You may lose autofocus depending upon the camera body and lens combination, particularly with the 2.0x. My DRebel along with the 10D cannot autofocus at below f5.6, so an f4.0 with 1.4 yields f5.6 and therefore OK for autofocus, albeit a bit more slowly. f4.0 with the 2.0X gets you to f8 and therefore you lose AF on most models.

How much is the image quality degraded using a TC?

Here's an image of a butterfly taken with my 100-400 f4.5/5.6L IS with the Canon 1.4X. Image was manually focused and hand held at the 560mm zoom (400mmx1.4=560mm). ISO of 800 used (and causes a bit of noise) to keep shutter speed up.

http://www.pbase.com/image/33369768.jpg

[drisley]

This picture was taken with the 135F2L and EF 1.4x Extender wide open at f2.8. It's probably the sharpest picture I've ever taken and that includes those without the extender, and also the many months I had the 70-200F4L.
It's even more impressive at 100%. I have many other pictures taken with the EF 1.4x that are ridiculously sharp.

http://www.fotop.net/albums/sharpnsmart/dragon_boats/CRW_2634.jpg

[jwhee0615]

Where are you getting the pricing for the 1.4 teleconverter? On B&H they list the Sigma at $169.95 and Canons at $269.95. Where do you get $800 and $1250? :?:

[jwhee0615]

Nevr mind I now see where you reference the lens and TC. Must need glasses or slow my reading down. Disregard.

[thedude]

Thanks for the examples! That makes the decision easier.

If Sigma (or Canon) states that autofocus will work with the TC, do I still have to worry about autofocus not working above a certain apeture?

I'm referencing pricing from www.digitalfotoclub.com

Resellerating:

http://www.resellerratings.com/seller2889.html

9.27 Pretty good, and better than BH. I bought my last two lenses from BH. Has anyone dealt with these guys before? Opinions?

[robertwgross]

[
Here's an image of a butterfly taken with my 100-400 f4.5/5.6L IS with the Canon 1.4X. ...

Interesting shot. You see the bright green spot? It neither makes the image bad, nor good. It is just interesting. Do you know what made it? Was it a water drop reflection off grass or something?

Cute.

---Bob Gross---

[dn7elson]

You see the bright green spot? It neither makes the image bad, nor good. It is just interesting. Do you know what made it? Was it a water drop reflection off grass or something?

I saw that and wondered myself. I did find a bit of lint or dust between the front lens and the 2nd one (guess I get to send it back to Canon to take care of), but I don't think that it was the cause as it hasn't shown up in any of the other shots.

[CyberDyneSystems]

Does anyone know of two images shot with both lenses for comparison sake?

Thanks in advance!

I did a side by side comparison here;
http://photography-on-the.net/forum/showthread.php?t=22421&postdays=0&postorder=asc&st art=0

This was the IS vesrion of the Canon... Vs the Sigma EX.

Many moinths later I really love the Canon.. but I have to admit that the old Sigma.. black and much lighter still triggers fond memories.

Either one is a good choice.

[Rayz]

Whenever I see questions about teleconverters, I usually get a sense that some people are just failing to distinguish between the 'objective' and the 'subjective'.

It has to be true that all teleconverters without exception will degrade the lens they are attached to. It's an additional piece of glass that's not designed for a specific lens and will unavoidably reduce the contrast of any lens.

However, that's not the whole story. There's a magnification factor which may, or may not, more than compensate for the degradation of the lens, in terms of extra detail. With the teleconverter, that fly on the lion's ear might be recognisable as a fly. Without the teleconverter it probably won't be recognisable as a fly.

A teleconverter essentially turns a superb lens into a moderately good lens of 1.4x or 2x the focal length and which is 1 or 2 stops slower, and turns a moderately good lens into a poor lens of 1.4x or 2x the focal length. There's no free lunch. (Although I'm not sure that's quite true. I'm a bit suspicious of cliches. I suspect that, in the Australian Bush, there are many free lunches in the form of edible berries :lol: ).

To put it another way, the 70-200/2.8 with 1.4x extender will become a 280mm lens of almost certainly lower quality than the 100-400 IS zoom at 280mm. The 70-200/2.8 with 2x converter will become a 400mm/5.6 lens of almost certainly lower quality than the 100-400 IS zoom. This would be an apples/apples comparison since both lenses would be 400mm F5.6 zooms.