? for Canon 800 mm lens users

I don't think anyone mentioned this but I would do at least a cursory check for AF micro-adjust. If you use liveview and contrast AF or manual focus it's not an issue but you could end up being disappointed with your shots if using normal AF and the camera and lens are out of calibration. If you don't know how to do a quick check just ask and I'll offer some suggestions otherwise have fun and post some shots.

Bob

Ecoh said:

I have been able to get a Canon 800 mm lens on loan for a day. I plan on going to an area where there are many eagles and a nest with eaglets. You must keep very far away from the nest site so that is the reason for the 800 mm.

I have a 7D, sturdy tripod with gimbal type head, and a strong husband to help me carry it the 3 mile walk to the eagles.

Can someone who has used this lens give me some tips on using it ? The largest lens I have is the 100-400 mm, is it much different using it ? Can I use a 1.4 tc ? Should I use mirror lock up ?

I will only have it for a day and want to make the best of it.

Click to expand...

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http://www.pbase.com/rwbaron

Great idea !

It will also help me get familiar with the lens while checking micro adjust.

Not sure about the distance I should set the target at while checking autofocus.
Any pointers ?

Canon recommends anywhere between 50 and 100 times focal length so that would be between 130 and 260 feet for an 800mm lens. On an APS C camera any lens at 50 times FL means a 2' x 3' rectangle fills the frame perfectly so that's a nice range for tight shots of raptors and such. I believe that range is a happy medium to provide decent AF performance from close focus to infinity. I do all my lenses at 50x and have had good results over the entire focusing range. Of course you'll have to be carefull with wind and heat distortion doing the AF MA and it would be ideal if you could find someplace indoor to check and adjust if necessary.

Last weekend I made the mistake of comparing all my long lenses at infinity focus outdoor shooting a tugboat about 3000 feet away over a river. It was about 55°F, calm, sunny and the river water was probably about 40°F. I used liveview and contrast AF and shot in silent mode on a heavy Bogen tripod and ball head. When viewing the images at 100% on screen they all look pretty much the same and I know my 300f4L is noticeably sharper than my 70~300DO. They all look sharp but obviously the conditions degraded the IQ to where any fine differences in resolution and micro-contrast were lost. I also can't tell any difference in these shots between my 300f4L with 1.4x, 100~400 and 400f5.6L all at f5.6 but shooting indoor demonstrates a noticeable advantage for the 400. Obviously there was vapor rising off the water that distorted the shots enough to neutralize the advantages of the superior optics. My point being you need ideal conditions to know the lens is adjusted to it's maximum performance.

I hope this helps.

Bob

Ecoh said:

Great idea !

It will also help me get familiar with the lens while checking micro adjust.

Not sure about the distance I should set the target at while checking autofocus.
Any pointers ?

Click to expand...

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http://www.pbase.com/rwbaron

If you use the TC, you need to use Live View focusing.

That may be good for static subjects, bot not much for moving targets.

Those are some great eagle shots!