Dr. Soon,

I have read your Videoscoping Web page on focusing, and I have some comments.

First, I believe there is one mistake. You say closer birds have more depth. Everything I have read
---and my own experience---says this is wrong. The closer you get, the less depth.

My experience is entirely with 35mm equipment, no digital, no video. That limits what I can
comment on. But there are some basic rules that apply to all.

I have a lot of experience shooting 35mm photos through scopes and binoculars. As you indicate,
autofocus can work sometimes, but all the conditions have to be right. In 35mm, autofocus won't
work at all in shooting with a scope or binoculars. There are several reasons for this. It is unfortunate that it can work with some digital and video cameras because that distracts people from the method that will work all the time under all circumstances.

It might seem like a helpful thing to have autofocus do "final focusing," but it is not good enough
for that really. It is as likely to ruin a good focus as to improve on a poor one. You should not use
the camera focus AT ALL, autofocus or manual. Focus only the scope while looking at the
focusing screen.

Whether the camera lens is set at infinity or not matters very, very little. Test this yourself so you'll understand. It is hard to put in words. In 35mm, setting the camera lens to a focus of 18" merely moves the lens forward a little and so a 50mm lens acts as a 55mm or 60mm lens. It magnifies the image ever so slightly more and has almost no effect on the focus. There is more of an effect with very short lenses like those used on digital non-SLRs and videocameras. Even so, that is merely distraction. Wherever the camera lens focus is, leave it there, put the camera up to the scope, focus the scope looking at the screen and begin photographing.

Macro mode is different in 2 or 3 ways. First, it focuses the camera lens closer-into the macro range. In this sense it is just taking the lens focus even closer than its normal close focus. Second, the focusing mechanism operates faster, making focusing quicker. Thirdly, some cameras with zoom lenses use only one focal length for macro, usually either the long end or the short end. I suspect in your case that macro mode on your camera selects the short end (because you say it gives a smaller image with more depth). Basically, macro mode is just an extension of ordinary focusing.

Because of all the difficulty with autofocus, you should always focus the scope yourself (Manually) and leave the camera lens alone. The autofocus is unlikely to improve on your focus. It is still an infant technology that is not as good as your eye. Do you want to be ready for anything or do you want always to search for just the right conditions to make autofocus work?

Your page says (under Method C), "In fact when a bird is too far away, correct focus on the scope can never be found with the scope focusing ring." Not true. If you can't find it with the scope focusing ring, it can't be found at all, because there is no other way. You must use the scope focusing ring.

As for vignetting, there are 3 basic causes:

1. Using too short a focal length. Use "normal" focal length-about what the eye sees-not wide
angle and from there to maximum zoom there should be no vignetting. [Incidentally, normal should be treated as 1X. Most noninterchangeable lens cameras go from about .7X (35mm in 35mm equivalent) to 2X (100mm in 35mm equivalent). What is called a "3X zoom" does not
magnify 3 times, but only 2 times.]

2. The camera lens and eyepiece lens are too far apart. Remove any filters on the camera lens and
eyecups on the eyepiece (unless the camera lens fits within the eyecup). If the camera lens is
recessed in its lens mount (with the recess increasing as you zoom in some models), reduce the recess if you can or get another camera that has less or no recess.

3. Using the aperture setting on the camera. In any kind of photography through a scope with the
camera lens still on, the aperture should be kept wide open. This can only be assured by using
manual exposure, not autoexposure. (With digital non-SLRs, sometimes (SOMETIMES) the
aperture can be adjusted on the camera successfully. But this may be impossible with a video
camera because the lens focal lengths there are even shorter. For the aperture to work, the camera's lens diaphragm  must be within the eyepiece's eye relief.)

I hope these suggestions will make your work easier. It is good that you have provided these pages on videoscoping, because no one else has done it. One day we will probably all move up to videoscoping, so you are the pioneer setting the way. We will all be glad then that you have done
all this work.

Bob Augustine
raugustine@tms-hq.com
Rockville, MD, USA