BirdForum is the net's largest birding community dedicated to wild birds and birding, and is absolutely FREE!

Register for an account to take part in lively discussions in the forum, post your pictures in the gallery and more.

Reply to thread

Message: <blockquote data-quote="Sout Fork" data-source="post: 958076" data-attributes="member: 34006">Jules:Does the main difference has to be to be optical ? SF:I don't know. I formed the question that way because that would seem tobe the implication of what the two quotes are saying however.Jules:The scope has a fixed aperture and it is the human eye that must adaptto the intensity of light. SF:For all practical purposes, often, a conventional telephoto is also afixed aperture device under real world conditions. Try shooting fastmoving passerines within their natural habitat which is often low lightunderbrush at a low ISO and a high enough shutter speed to freeze actionand you end up going to aperture priority mode and opening the aperturewide open anyway.Jules:The camera lens has to use a more sophisticated system in order to allowthe film or the sensor do get the required amount of light - theduration is controlled within the camera but the aperture is variableand this is done automatically inside the lens with an electronic signalthat triggers a change in aperture (or mechanical for the older lenses).SF:But you also have aperture priority within the camera body. That is youcan control light either by the shutter or the aperture. In my case Iuse aperture priority and therefore have TTL auto metering through thelens and thus have a full auto exposure mode. This works out well for mebecause, as I say, whether or not I would use a scope or a telephoto Iwould be probably shooting in aperture priority with the lens wide openanyway.Jules:This system also allows control over the depth of field by varying thespeed/aperture equation while keeping the intensity of light constant.SF:This might make some sense with regard to relatively low powertelephotos, say about 15x (500mm) or less, but when you are talkingabout a scope at 38x (the equivalent of a 1910mm tele) as is my casethere is no depth of field to control. The only option is where to putthe paper thin DOF not control it. Do you want the flanks or the eyes ofthe bird in focus and that's about it.Jules:The third difference is focus control. The scope has a control made tobe adjusted by the user while the camera lens does this automaticallyfrom the camera. SF:At the powers and light levels that I typically shot at AF is anon-starter. As I said I often shot at low light levels in very complex3D environments where there is twigs, branches, leaves at varyingdistances around the target and I have found no AF system with the intelligenceto know the difference between a bird and the leaf 3 feet in front of it.And even if it did it would not know if I want to focus on the eyes orslightly shift it to the flight feathers for instance. I guess I'm oldschool when it comes to focus - I trust what I see in the viewfinderwith my eyes not the machine.Jules:The better lenses even add vibration/shake reduction. SF:I have SR in the body of one of my cameras. I tried using it at highpowers with very poor results. I finally got hold of someone at Pentaxthat seemed to know what he was talking about. He told me to turn it off.He said that SR was to control for the relatively deep slow motion of ahand held relatively low power lens. A high power scope mounted on adecent mount and tripod does not benefit from SR. In fact it makes itworst because a tripod, to the extent it allows movement, creates veryshallow fast vibrations and with SR on only makes it worse. PerhapsCanon or Nikon have much better systems I really don't know. Anyway......please don't understand this as argumentive and in your face.This is just one man's opinion based on his limited experience. Take care to all,SF A few examples of the kind of shots I prefer if I can get it...</blockquote>

Verification