BetterPhoto Q&A
Category: New Answers

Mingming Mia Bowerson		A camera and Lens question I have a photography courses on other place. I have 3 questions on my comprehension tests, I hope I can find somebody help me from here. 1. A 100mm lens produces an image twice as high and twice as wide as that produced by a 50 mm lens. My answer is False. Because I know It's right, but it has to be on a condition of taking the image in a SAME DISTANCE, Otherwise I could still use the 50 mm lens, walk close the object to make an image as that twice as high and twice as wide as well. 5. After you focus a zoom lens, it can remain in focus as you change the focal length. My answer is False. Dennis P. Curtin wrote in his book, said "Tip, zoom before focusing since zooming can through off focus." And I do have experienced it often that zooming through off focus. 10. To avoid linear distortion when photographing a tall building with a 35mm camera, you should position the camera so that the face of the lens is parallel to the face or side of the building. My answer is False. Because our book Camera And Lens p30. said, "...keep the back of your camera parallel to the face of the structure you are photographing." I know that normally the face of the lens is parallel to camera back. But I don't know how the PC lens works, I assumed that we have to keep the camera back parallel to the face of the building and move the face of a PC lens to eliminate linear distortion. But My student advisor said all of the three answer should be TRUE. What do you think? Please help! To love this question, log in above August 22, 2005

Kerry L. Walker		I think you are trying to read each question as a trick question. You can attach conditions to any question and make it fals as there are few absolutes in this world. To love this comment, log in above August 22, 2005

Jon Close		#1 - True. You can safely assume "all other things (focus distance, film/sensor size, aperture, lighting, etc.) being equal/unchanged." #5 - False. You are correct that this is sometimes true (parfocal zooms) and sometimes not (varifocal zooms). #10 - _Both_ the front of the lens and the film plane need to be parallel to the face of the structure. The test statement is very slightly defective as it assumes the lens face and film plane will always be parallel. True with normal and perspective control (shift) lenses, but not necessarily true with tilt lens or field camera. To love this comment, log in above August 22, 2005

Mingming Mia Bowerson		Thank you Jon. But I still think the #1 question should be false, because the key is at the SAME DISTANCE, without the key, the answer should be false. I consider the photography is mostly art. But when we talk about photography technically, I consider it is science, optical science. So I don't think I was trying to read each question as a trick question, and I believe THERE IS absolute TRUE or FALSE scientifically in this world. If the #1 question with the condition of taking the image at the same distance, then the answer will be absolutely TRUE. If not, it will be false, because I can take the image closer and make it bigger. Thanks again Jon. To love this comment, log in above August 22, 2005

- Gregory LaGrange Contact Gregory LaGrange Gregory LaGrange's Gallery		Image is higher and wider, not the angle of view, which sounds like what you're thinking of. Picture with 100mm and 50mm, when you get your 4x6, the one done with the 100mm the image of the person will be bigger height wise and width wise. Third question, it's a basic course sounds like so I don't think all possibilties even entered the mind of who made up the test. So might as well be true To love this comment, log in above August 22, 2005

This old forum is now archived. Use improved Forum here Report this Thread