Stupid question: why can I stop up to 22 on a 4.5-5.6??

max10

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Hi,

Brand new to the forum. I have a question about f stops and aperture. Take for example my telephoto. It states it is f4.5-5.6. So how come I can have a reading of f5.6 all the way to f16 or higher? Is an f stop on my camera different from the numbers of my lens? I have obviously been missing something...

Thanks in advance, this noob appreciates it.

M
 
You have a variable aperture lens. The maximum (largest opening) will be f/4.5 at the shortest focal length, but f/5.6 at the longest.

Apertures between f/5.6 at f/22 are the same throughout the zoom range. Smaller than f/22, you need to be in the long focal length end of the range.
 
Your telephoto is in fact a zoom lens. The f/4.5 - 5.6 values engraved on the lens are the maximum apertures of the lens -- f/4.5 at the wider end and f/5.6 at the longer end. Smaller f/stop values are possible and in fact often desirable. What the lens is telling you is that you can't achieve larger apertures than those listed. A different lens with the same focal length range might be f/3.5 - 4.5 which would then extend it's range beyond what your lens is capable of providing. It'll cost you more.

Joe
 
Hi,

Brand new to the forum. I have a question about f stops and aperture. Take for example my telephoto. It states it is f4.5-5.6. So how come I can have a reading of f5.6 all the way to f16 or higher? Is an f stop on my camera different from the numbers of my lens? I have obviously been missing something...

Thanks in advance, this noob appreciates it.

M

Ok, if I understand your question correctly - the ratings on the lens are the maximum aperture settings the lens is capable of at at given focal distance. Take my 70-300 mm Nikkor for example, it's rated at f/4.5 to f5.6. This means that the widest the aperture will open is f/4.5 at 70 mm and f/5.6 when it's zoomed out to 300 mm.

Now these are the maximum apertures. However you can set the aperture on the lens so that it is a higher F number at these focal lengths. The higher the F number, the less light your actually allowing into the lens - the reason that it seems backwards is that F numbers are actually fractions, so the higher the number goes the more you are "stopping" down the lens and the less light that actually gets through to the sensor.

So you can stop down the lens at pretty much any focal length you want by adjusting the aperture. This is done by using the controls on your camera, but really what it is doing is telling the lens to reduce the aperture opening and the lens does. On some lenses you can actually control the aperture manually by adjusting the lens itself, you'll see that more commonly on older style lenses designed for cameras that didn't have all of the whizbang electronics of the modern DSLR.

But the numbers you see on the lens represent the absolute maximum you can open the aperture for that lens at a given focal length. Hope that helps.
 
Thanks everyone! That helps a lot, and I think I finally get it!
 
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