Anker, et al: Another RCSE member already addressed this correctly, but I thought I'd add a bit more to help clear up the misconception that the Nikon D70 (and other digital single-lens-reflex cameras) increases the focal length of the lens that you attach. I haven't reviewed the entire thread; if what I offer below has already been covered, please forgive me.
When you attach your 70-300mm lens to your Nikon D70, (or your 80-200 to your Canon Digital Rebel, or any other lens, for that matter) the focal length of the lens does not and cannot change. The focal length derives from the distance of the rear nodal point of the lens to the imager (or film plane on a film camera) when the lens is focused at infinity. That distance doesn't change when you attach the lens to a digital camera, and neither does your focal length. What changes on all but just a very few digital SLRs is the picture area that you see (some digital SLRs have 35mm full-frame imagers -- they're REALLY expensive). The lens you attach retains all its mechanical properties: magnification, minimum and maximum focusing distances, available apertures, etc. Most importantly for this discussion, your lens still transmits the same circular image area that it transmits on any camera to which it is attached. You only see a rectangular image because that's what the camera designers had to work with when they first started putting film into cameras. Rectangles and squares are easier to fit onto film and more manageable than circles, and with circles, images get fuzzy at the edges. Think of it this way: With a 35mm film camera, you see a certain-sized picture area that happens to fit neatly onto the film strip; that rectangle is inside the circle of the image the lens transmits. You don't see the circular image because what you see in the viewfinder must match what you get on film. No one would buy a camera that didn't do that. But since the digital SLR imagers are smaller than the image size you get on a 35mm film camera, you see a smaller portion of the circular image that the lens transmits. It appears that you have suddenly increased your lens focal length, but you haven't. Your lens will not exhibit any of the physical properties of a lens that's actually of the increased focal length. Focal length for focal length, the smaller digital imager gives a smaller field of view of the same image, making it appear that your lens has a greater magnification than it actually has. Sorry for the novel. I'd like to add one more point. I was in photographic retail sales for a while, and most people who bought digital SLRs from our store were excited about the supposed advantages of that magnification factor. It was a selling point to anyone who didn't fully understand what they were actually getting because everyone wants that really long lens so they can reach out and photograph little Johnny when he's in right field and mom is taking pictures from behind the plate. Besides the lack of increased focal length, the big disadvantage of the magnification factor is that you lose the full field of view at the wide angle end of your zoom lens. I've been a photographer of one sort or another for 20 years, and I've learned to appreciate the wide-angle lens. A 20mm lens on a film camera can produce some very interesting images. But that same 20mm lens placed on a digital SLR with a magnification factor ceases to provide that lovely wide 20mm field of view, and to me, that's a bad thing. By the way, once I learned what the magnification factor really meant, I stopped using it as a selling point with customers, and I fully explained this myth to my customers and to the students I taught in our store's basic photography and digital photography classes. Again, sorry for the novel. Cheers and happy sailplane photographing!! Scott in Chandler, Arizona. -----Original Message----- From: Anker Berg-Sonne [mailto:[EMAIL PROTECTED] Sent: Thursday, February 24, 2005 2:54 AM To: soaring@airage.com Subject: [RCSE] Digital photography There was some discussion quite a while back about what cameras to use for digital photography of planes. I recently purchased a Nikon D70 and have two lenses. The kit 18-70mm and a zoom tele 70-300mm - with digital you get the equivalent of 1.5 times the lens, so I really have from 35mm to 450mm. Anyway, the best thing about this camera is that when you press the button it takes a picture, no shutter delay. Even better, you can now get the camera with the kit lens for under a grand with mail in rebate. Anker Anker Berg-Sonne [EMAIL PROTECTED] RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
