7-200 with TC - Hunting and image degradation

[Medic1]

Has anyone had problems with their 70-200 hunting for focus with the 1.4X TC? I have only had it happen a few times out of a couple hundred pics with the TC on, but its still annoying.

Also, how much do you figure the TC degrades image quality with the 70-200 f4L? I have noticed I get more pictures that turn out unusually soft with the TC.

[CyberDyneSystems]

TCs can allways degrade image quality to a certain degree, especially noticeable on Zooms,. although the 70-200mm zooms are perhaps the best zooms for use with a TC of any.

It helps to stop down a bit.. say to at least f/8

Hunting and overall slowing of AF is indeed normal.. varying with the f/stop of the lens and TC combo. @ f/5.6 max ap on your particular combo. some degree of effect on the AF is to be expected.

All of this is covered to some degree in the T-con sticky thread.

[robertwgross]

I guess you know that the x1.4 TC will cause a loss of a stop of light. That might put you over the limit for autofocus operation. It might put you right around the marginal point, so in difficult light, it sort of works inaccurately part of the time.

As I have stated previously, there was an Outdoor Photographer magazine article by George Lepp where he addressed the image degradation. He said that if you start with a mushy lens and add a x1.4 TC, you will get a super mushy image. If you start with a very sharp lens and add a x1.4 TC, you can get a sharp image with only 10% degradation. With the sharp lens and add a x2 TC, you get it with 20% degradation.

The only problem is that we don't know exactly what he means by 10% or 20%.

---Bob Gross---

[Medic1]

Thanks....I figured that it was normal, but it just seems as if I am getting quite a few unusable images as compared to before. For every say 10 images before, I may have had a couple soft pictures....now with the TC...I would say 50% of the images are soft, even with a 1/2000 shutter speed and good light