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Old Aug 14, 2006, 8:59 AM   #1
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hi all, please guide me with this, about the fix focus length lens & the zoom lens, how do they different from the outcome? is fixed length better than zoom if using the same exposure setting? or the optics used quality is different?
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Old Aug 14, 2006, 10:54 AM   #2
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Typically fixed focal length lenses are considered optically superior to zooms - less complicated. Fixed focal length lenses are also usually faster (wider aperature) than zooms as well.

I haven't done any tests - but just glancing thru my pics, I much prefer the look of my 50mm shots from my M50/1.7 or F50/1.7 over similar shots done with the 18-55 or 50-200 at around the same focal length.

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Old Aug 14, 2006, 10:59 AM   #3
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Basically if a lens is made to be a fixed lens, then it is set at one focal length, i.e 135mm. The optics are manufactured to give the best picture at that length.

With a zoom lens, say 100mm-300mm, then the optics are trying to give a focused image at varying ranges and to do that there has to be some compromises and one of those compromises is usually less than SHARP SHARP images.

People refer to lenses as being Tack Sharp. Trust me when I tell you a Prime lens (fixed lens) will almost always be sharper than a variable lens (zoom)

The longer the focal range the more the glass has to compensate. examples 70-300 (x4), 80-320(x4), versus 18-55 (x3).

There is no such thing as the perfect lens though some do come close...:lol: It is all about compromise, do you want the most focused lens then you lose the zooming ability, you want zoom then be prepared to lose some sharpness.

Hope this helps




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Old Aug 15, 2006, 4:53 AM   #4
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thnks crashman, i got it clear now. basically just wondering why some fixed focal lens sell so expensive!!, the faster the better?
if i normally wouldn't be shotting in low light situation, should i still need the prime lens?
i am not a perfectionist so can live without the damn sharpness so, will find those zoom lens first. tQ
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Old Aug 15, 2006, 5:48 AM   #5
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joebgoh wrote:
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if i normally wouldn't be shotting in low light situation, should i still need the prime lens?
Some lenses, like a real macro lens, are usually single focal length. If you have no special needs you will not require one.
i am not a perfectionist so can live without the darn sharpness so, will find those zoom lens first. tQ
Prime lenses (single focal length) used to be much better than zooms, but modern zoom lenses are pretty sharp. The gap isn't that great anymore.
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Ira
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Old Aug 15, 2006, 10:46 AM   #6
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joebgoh wrote:
Quote:
thnks crashman, i got it clear now. basically just wondering why some fixed focal lens sell so expensive!!, the faster the better?
if i normally wouldn't be shotting in low light situation, should i still need the prime lens?
i am not a perfectionist so can live without the darn sharpness so, will find those zoom lens first. tQ
My observation, which is very subjective, is that fast lenses are often of a higher quality in all aspects. I think it is because they, due to the glass elementquality required for high speed, would be expensive anyway. Then the manufacturer might as well add build quality and even more expensive ED glass. The buyer who is prepared to pay the high price is probably prepared to pay the even higher price for added quality. Result: super high quality lenses, super high price. (A*, F*, FA*-lenses, Limited series lenses)

Kjell
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Old Aug 15, 2006, 8:39 PM   #7
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just to throw a stone in the fire here i'll say this. i use to think my M200 f4 was a sharp lensand it is. it's a great lens and i'd recommend it to all, but.. after getting the A70-210 f4 i have to say it's sharper thru out the range.. of course it's twice as big and 3 times the weight. the M80-200 f4.5 is also just a little bit sharper thru out. i'm keeping the m200 and the a70-210. with ext tubes the m400 is a greatlong distancefocus macro. the a70-210, what can i say.. the m80-200 f4.5 is available if anyone wants a mint zoom in this range..

roy
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