fixed Zoom vs variable zoom lens


Nov 15, 2009
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#1
Hi! i'm using a Sigma variable zoom 18-250mm for my Nikon D5000. noticed that at the extreme zoom, the pix tend to not be very sharp. does fixed zoom lens take sharper pix?
 

spree86

Senior Member
Feb 3, 2009
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Bishan
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#4
Hi! i'm using a Sigma variable zoom 18-250mm for my Nikon D5000. noticed that at the extreme zoom, the pix tend to not be very sharp. does fixed zoom lens take sharper pix?
Lenses with big zoom range like the 18-250 are known to performer poorly at optical quality, especially at the longer ends. Even a kit will often be sharper. There are good and bad constant aperture lenses too.
 

Blur Shadow

Senior Member
Sep 17, 2005
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#5
Lenses are generally designed to suit each specific needs.

In your case, a compact super zoom is created for the user's convenience at the expense of image quality.

Generally speaking, the reverse is true - large aperture zooms are designed with high image quality in mind.

Note that this is a general statement that may not be true in all circumstance. Got to consider each lens individually.
 

trd2970

Senior Member
Jun 8, 2005
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#6
At the most extreme ends, consumer grade tele zooms generally do not render sharp images, it gets worse if shot at its widest aperture.
 

Shizuma

Senior Member
Mar 19, 2012
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#7
Prime lens are always very sharp because focal length is fixed, the elements can be optimized for the focal length,
unline for variable focus which requires a compromise
 

lewissac

New Member
Sep 20, 2011
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#8
To me, if I shoot portrait I'll use prime lens. They gave me exceptional image quality (not to mention the great backgrd bokeh). For normal shoot like street, I'll use the fast zoom lens. And for travel, long zoom range. So, to me what really matters is what lens you prefer depends on what do you want to shoot.
 

rhino123

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Staff member
Sep 1, 2006
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#9
Most fix focal length lenses (prime lens) are sharper when compared to zoom lens but that was not always the case though. Anyway, if sharpness is the only thing TS is looking at, then... yeah, in general prime lens is sharper.

A zoom lens (especially those with much bigger zoom range) will have to have some compromise in IQ... which in my opinion can actually be corrected to a certain extend during editing so it is okay.

However if TS is actually asking about fix and variable aperture, then it is a different matter altogether. In actuality, I do not believe that fix aperture or variable aperture would have much to do with sharpness of the photo, although in general... a fix aperture zoom lens is always more expensive and 'premium' then a variable aperture zoom lens of similar zoom... and for that type of money, people would definitely want something that is sharper, more contrasty had better looking bokeh as compared to the variable aperture lenses.
 

giantcanopy

Senior Member
Feb 11, 2007
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#10
Hi! i'm using a Sigma variable zoom 18-250mm for my Nikon D5000. noticed that at the extreme zoom, the pix tend to not be very sharp. does fixed zoom lens take sharper pix?
Apart from the discussion of optics, just make sure the lack of sharpness is not due to handshake at the 250mm end of things.
Poor stabilisation during shooting gets magnified at the tele end of your zoom.

Ryan
 

catchlights

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Sep 27, 2004
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#11
Hi! i'm using a Sigma variable zoom 18-250mm for my Nikon D5000. noticed that at the extreme zoom, the pix tend to not be very sharp. does fixed zoom lens take sharper pix?
technically speaking, yes, constant aperture zoom lens produce better quality images.

you want convenient of great coverage of high power zoom lens, than you have to make some compromise on the quality, but as long you willing to live within it limitation, it won't be a big issue.

btw, poor camera handling technique will also affect image results, regardless what grade of cameras or lenses you are using.
 

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