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Photo Forum / General Photo Topics / General Topics / May 2005Magnification Factors
I'm not sure how to interpret magnification factors. I'm looking into the possibility of picking up a wide-angle converter lens for my HD camcorder (URL may wrap): http://www.sonystyle.com/is-bin/INTERSHOP.enfinity/eCS/Store/en/-/USD/SY_Display ProductInformation-Start?CategoryName=hid_pr_p_new20accyprod_dcc&ProductSKU=VCLH G0872&TabName=comp&var2= It says that it has a magnification factor of 0.8, and they want $500 for it, although I have a special coupon to get it from $400. But doesn't seem like 0.8 would be much of a change from the 1.0 of the lens itself - not much for $500 or even $400. However, I'm not sure that I know how to interpret that 0.8 number. Is that a multiplier on the focal length? Does it mean that, if I were taking a picture of a ruler and the width of the image reads as 1.0 units on the ruler, that with this adaptor, it would read 1.25 (1/0.8) units?  Signature(Preferably reply to the newsgroup, please. If you reply by Email, I will sincerely try to receive your message, but it will probably get buried in spam.) > I'm not sure how to interpret magnification factors. I'm looking into > the possibility of picking up a wide-angle converter lens for my HD > camcorder (URL may wrap): http://www.sonystyle.com/is-bin/INTERSHOP.enfinity/eCS/Store/en/-/USD/SY_Display ProductInformation-Start?CategoryName=hid_pr_p_new20accyprod_dcc&ProductSKU=VCLH G0872&TabName=comp&var2= > It says that it has a magnification factor of 0.8, and they want $500 > for it, although I have a special coupon to get it from $400. But [quoted text clipped - 6 lines] > units on the ruler, that with this adaptor, it would read 1.25 (1/0.8) > units? The 0.8 factor means that the adapter reduces the focal length of the lens to 80% of its native value. As for your example, no that is not how it works. These devices are about the only way to get a significantly wide angle. 80% makes a lot of difference in the appearance of the image. Jim >>However, I'm not sure that I know how to interpret that 0.8 number. Is >>that a multiplier on the focal length? ... > The 0.8 factor means that the adapter reduces the focal length of the lens > to 80% of its native value. OK, I'll ponder it in that light. For example, in 35mm-camera terms, wherein a "normal" lens is about 50mm, it would produce the effect of a 40mm lens. Signature(Preferably reply to the newsgroup, please. If you reply by Email, I will sincerely try to receive your message, but it will probably get buried in spam.) >>>However, I'm not sure that I know how to interpret that 0.8 number. Is >>>that a multiplier on the focal length? ... [quoted text clipped - 4 lines] > wherein a "normal" lens is about 50mm, it would produce the effect of a > 40mm lens. But 80% of 35mm is 28mm; many 35mm photographers find it useful to carry (or at least, own) both those focal lengths. I think that if your fixed lens gives a maximum width of view of 100 feet at a particular distance from the camera, then putting an 80% adaptor in front of the lens will give you a width of 125 feet (which looks to me to be agreement with your original calculation). Whether that is worth the money is up to you. There may be cheaper gadgets out there that can do the same trick, but less elegantly and perhaps with a greater effect on image quality, that would be worth trying first. A 72mm fitting means that this is a pretty hefty lump of glass. Signature-- ^^^^^^^^^^ -- Whiskers -- ~~~~~~~~~~ > >>However, I'm not sure that I know how to interpret that 0.8 number. Is > >>that a multiplier on the focal length? ... [quoted text clipped - 4 lines] > wherein a "normal" lens is about 50mm, it would produce the effect of a > 40mm lens. Yes, but in that case, the difference would not be great. However, if you install the 0.8 adapter on a lens with a 35mm focal length, the difference would be much greater. Jim.) |
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