Long Range Focus with Canon 70-300mm

[clemsgn]

Does anyone else have experience with this issue. I recently tried to take some shots out the window during a flight with Southwest Airlines. I could not focus this lens (mostly at 300mm) with AF or manually even slowly. The weather was very clear out at the time and I had no problem seeing the same areas clearly with my eyes (although not as close obviously). This didn't seem right as when normally spinning the focus ring back and forth, it was nice and sharp. For some reason this lens just never gave me that nice sharp focus no matter how precise I was with the adjustment. As I focused it got a bit better and then it started to get worse like I passed the point of best focus. It really wasn't close to good focus at all. I didn't think this would be due to haze in the atmosphere or on the window, because I can see the landscape fine with my bare eyes. Just in case you may wonder, I had my Viewfinder Diopter set just right for my eyes.
This lens really has fantastic optics for what it is and always gets nice sharp shots when zooming in on buildings, signs & people etc.from a distance of roughly a mile or less. I wonder if being up at 37,000 ft (7 miles) in a plane would cause this ? I've tried to shoot the moon many times and never really got a perfectly sharp photo before. It was acceptable for a 300mm lens, but not as sharp as I'd like to get.
So do all telephoto lenses exhibit this trait or do I have a problem with my lens ? I'm going to photograph a space shuttle launch soon and I will be about 6-7 miles away, so I anticipate the same problem. I'm going to try a 2X extender as well, so even though they can degrade the quality, I hope it's a bit better on the ground than I had up in the air without the extender. Any advice or info from the educated members on this forum would be much appreciated.
Thanks again, Clem

[RichardTaylor]

Don't believe your eyes.
(1) you are trying to focus through an number of layers of transparent material.
That is problem #1
and
Was the subject low contrast?
Then you have another problems.
(2) Cameras need something contrasty to focus one


Try your lens on something contrasty, at long range, on a clear day.

Here is an example, not a super clear day, with the same lens.
The city is about 6 miles away (as the crow flies).
Larger version (1200x763 pixels) is avaible via flickr.



I have not used a T-Con for many years.
You may want to read this thread.

http://photography-on-the.net/forum/...ad.php?t=41922

[clemsgn]

Originally Posted by RichardTaylor

Don't believe your eyes.
(1) you are trying to focus through an number of layers of transparent material.
That is problem #1
and
Was the subject low contrast?
Then you have another problems.
(2) Cameras need something contrasty to focus one


Try your lens on something contrasty, at long range, on a clear day.

Here is an example, not a super clear day, with the same lens.
The city is about 6 miles away (as the crow flies).
Larger version (1200x763 pixels) is avaible via flickr.



I have not used a T-Con for many years.
You may want to read this thread.

-=FAQ=- Teleconverter/T-Con Tele extender FAQ - Canon Digital Photography Forums

Thanks for the reply. I was hoping that the layers of glass on the aircraft had something to do with it, but I keep remembering how well I could see through that same glass with my own eyes and the same area was very much in focus. Through the viewfinder and the actual shots taken were quite blurry. I actually deleted the bad pics right away, so I don't have any evidence to share.
The real test will be at Cape Canaveral later this week from a distance of 6 - 7 miles. I had read that same info on the Teleconverters....in fact I already had it bookmarked. The extender I will be using is one of the best that will work with my 70-300mm, the Kenko Pro 300 DG 2.0. I realize that it will take away some of the sharpness, but I want to get as close as I can to try and do my best. Time will tell
Thanks again for your response, Clem

[clemsgn]

Originally Posted by RichardTaylor

Don't believe your eyes.
(1) you are trying to focus through an number of layers of transparent material.
That is problem #1
and
Was the subject low contrast?
Then you have another problems.
(2) Cameras need something contrasty to focus one


Try your lens on something contrasty, at long range, on a clear day.

Here is an example, not a super clear day, with the same lens.
The city is about 6 miles away (as the crow flies).
Larger version (1200x763 pixels) is avaible via flickr.



I have not used a T-Con for many years.
You may want to read this thread.

-=FAQ=- Teleconverter/T-Con Tele extender FAQ - Canon Digital Photography Forums

Yeah, I was hoping that shooting through the window was part or most of the problem, but what bothers me is I could see much clearer with my own eyes through that same window at the same landscape. The land below was very visible and some things were small, but I could still see clearer than the lens.
I realize the camera needs something contrasty, but I was focusing manually and the best it would do was pretty blurry. I wonder if there's something wrong with my lens or shooting out a plane window with a 300mm just won't focus well, period ? Anyone else have experience with this as well ?
As far as the T-con, I am getting the Kenko Pro 300 2X which I read is one of the better ones out there. I know it would be better to have a 600mm prime, but I just want to get a closer shot of the space shuttle. I will take some practice shots before it launches and if it doesn't cut it, I will just use the 70-300mm alone.
Thanks for your comments, Clem