Fixed vs Variable Aperture Lenses


I’m sure many of you will be asking Santa for a new lens this Christmas.  But, before you send in your wish list to you will want to think about if you want a fixed aperture lens or if you would be okay with a variable aperture lens.

Variable aperture lenses are going to be your cheaper lenses.  And you will know because you will see two aperture numbers on the lens.  For instance, the Tamron 18-270mm, F 3.5 – 6.3 is a variable aperture lens.

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You can tell because there are 2 different apertures listed in the description (and on the box and the lens itself), F 3.5 – 6.3.  When you are zoomed out at the widest (70mm for this lens) you can shoot with an aperture of 3.5.  However, when you are zoomed at the tightest you will only be able to shoot with an aperture of 6.3.  When you are shooting at focal lengths in between your largest aperture will also be somewhere in between.  The focal length and aperture are dependent on one another.  The longer the focal length, the smaller the aperture.  Why does that matter?  Because you are letting less light into the lens when zoomed in all the way.  On paper it looks like a great lens.  It’s priced right at only $449, it has a wide range, and it is small and compact.  But, if you want to shoot indoors with a lens like that and only want to use available light you will not be able to.  Especially when zooming.

Compare that lens to the Tamrom 70-200mm F 2.8 lens at $1499.

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What are you getting for $1000 more?  We know we are getting a fixed aperture because there is only one aperture listed.  The fixed aperture means at 70mm you can shoot at an aperture of 2.8 and at 200mm you can shoot at an aperture of 2.8.  The aperture and focal length operate independently.  Besides the fixed aperture you are also getting a better lens with more precise focusing and image quality, which is why the lens is $1000 more.

You have to ask yourself what you will  be shooting mostly.  If you will be shooting sports, for instance, and will be outdoors most of the time, than a variable aperture lens is fine for you.  If you will be shooting indoors where you need a wide aperture to allow a lot of light in then you will most likely be very disappointed with a variable aperture lens.


  1. Ada says

    great explanation! I always send people here when helping them with questions like this.

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