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Old Mar 5, 2007, 3:23 PM   #11
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that was a great link, thanks! really helps imagine, and convinced me to now buy the tamron af lense I was looking at.

*I decided that since I am getting a DSLR, I have to stop trying to relate the lense specs with other things, and just look at it itself. Once I buy the new 70-300mm lense, along with my 18-55 kit lense that is coming with the body, I'll have an idea of how the specs relate to my camera and will be able to visualize how it will look.

**For people having a hard time trying to understand these things, just remember to not let it get you down, after all it's about the photography, not the knowledge of the specs when it comes down to it. So go out and shoot first, then worry about lense measurements
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Old Mar 23, 2007, 11:37 PM   #12
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While the field of view changes when you use old lenses on Pentax dSLR cameras (by a factor of 1.5x) you won't get any greater magnification. I often see Ebay adverts suggesting that a 50mm lenseffectively becomes a 75mm lenswhen used with a dSLR- not true. What you doget with a digital cameraimageis a cropped one e.g. If you take a pic on a film camera you get the whole picture that you'd expect from the 35mm format. Then if you should crop that image to66% of itsoriginal size (you could take a pair of scissors to your printed pic and snip equally away from all four sides). The remaining portion of that image is what you'll see when using that same 50mm lens onyour dSLR -the field of view may be equivalent to that of a 75mm lens on film but the magnification properties of a 75mm lenswill always be greater than those of a 50mm. So sadly, no free lunch.
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Old Mar 27, 2007, 12:23 AM   #13
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The image that is thrown onto the sensor is cropped, but the image that the sensor captures is full resolution. And because the image thrown onto it is cropped, it IS effectively "magnified", because the sensor captures an image that is 1.5 times larger than 35mm film would capture. So, yes, you do get "free" magnification.

50mm is around how much the human eye would "see"referenced to35mm film, as "standard". It's an approximation, not an exact science. About 8mm on a typical point and shoot digital camera is about "standard". Your eye can see around 150-160 degrees, but when taking a photo with a 35mm film camera, then printing it at around 6"x4", then holding it up about 40cm from your face, it will appear around the same size as the original scene. It's only approximate.

In layman's terms, a50mm lens captures an image about 6 times as wide as a 300mm lens. This means the angle of view is about 6 times wider. However, although this is close, it's not EXACTLY correct. The way to work it out is more complex.

The "multplication factor" used with point and shoot digital cameras is only a convenient way for people to see what sort of zoom they will get on the camera. A digicam with a 28-280mm equivalent is quite different to one with a 35-350mm equivalent.
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