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PostPosted: Mon Aug 04, 2008 9:34 am 
I saw in the review on the nikon d40 and i have a question about it, when Gordon changes the F number it goes all up to 32 tought the kit lens is 3.5-5.6. I tought max Aperture was 5.6 then? This may be a stupid question but im really green on dslr and like to know more before i buy one :)

Can someone please tell me more about that situation if u understand what i mean?

Also wanna say that im not 100% on english and thats why its much easier to get a litte help on forums, i personally think its easier to understand by reading forums on this things.

Regards Seb


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PostPosted: Mon Aug 04, 2008 10:43 am 
Hi Seb,

Apertures are confusing to everyone at the start. :) F32 is a very small aperture which lets a small amount of light in, so the higher the F-number, the smaller the aperture. The max aperture of the 18-55mm is described as F/3.5-5.6 because it is not a high end lens so does not have a fixed max aperture throughout the zoom range. At 18mm the max aperture is f/3.5 and at 55mm the max aperture is f/5.6. The max aperture gets smaller as you zoom in further.

More expensive lenses have what is known as a constant aperture. They have the same max aperture throughout thee zoom range. For example, the 17-55 f/2.8.

I hope that helps.

Mark


Last edited by Markh on Mon Aug 04, 2008 10:43 am, edited 1 time in total.

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PostPosted: Mon Aug 04, 2008 10:43 am 
18-55 f/3.5-5.6 means the maximum aperture at 18mm is 3.5 and 5.6 at 55mm.

The maximum aperture is the smallest number because you get the f-number by dividing the focal length by the diameter of the entrance pupil(hole made by aperture) so the smaller number = a larger opening. Therefore, the smaller is the maximum aperture and the minimum aperture is in fact the largest number.


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PostPosted: Mon Aug 04, 2008 3:12 pm 
ah ok i understand it a bit better now but still i dont get how Gordon on the review can put the apature(f) number all up to 32 when it says 3.5-5.6 on the lens`?


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PostPosted: Mon Aug 04, 2008 3:43 pm 
Fouracesswe wrote:
ah ok i understand it a bit better now but still i dont get how Gordon on the review can put the apature(f) number all up to 32 when it says 3.5-5.6 on the lens`?


3.5-5.6 is the range of the maximum aperture (largest hole). Remember that this is adjustable. A lens's aperture can be closed and made smaller but inputting a bigger number. F/32 is the minimum aperture (smallest hole). So at 18mm, this lens can have an aperture anywhere between f/3.5 - f/32 and at 55mm it can have an aperture between f/5.6 - f/32.

Any other questions? 8)

Mark


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PostPosted: Mon Aug 04, 2008 3:45 pm 
ah thanks now i get it all :).


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PostPosted: Mon Aug 04, 2008 3:47 pm 
well i can ask a small question, lens hood does they effect your quality of your picture when shooting when its not that much sun? Also shall Neutral UV filter always be on, or theres any - with that?


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PostPosted: Mon Aug 04, 2008 3:54 pm 
Fouracesswe wrote:
well i can ask a small question, lens hood does they effect your quality of your picture when shooting when its not that much sun? Also shall Neutral UV filter always be on, or theres any - with that?


I nearly always use a lens hood when I'm shooting. As you say they are more useful when you're outside and it's sunny, but they don't have a negative affect on quality whenever they're used. Well - unless you're using a pop-up flash and a big enough lens with hood - this could cast a shadow on the very bottom of the image but it's never really a problem, and in which case just remove the hood. Lens hoods also offer some physical protection for the front lens element.

As for UV filters - it's personal choice really. I don't use them at the moment but may pick some up at some time in the future. There's always the possibility that adding more to the lens could affect quality, but this isn't noticeable from what I've seen with other filters.

Mark


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PostPosted: Mon Aug 04, 2008 4:13 pm 
Thanks Mark your great!


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PostPosted: Mon Aug 04, 2008 5:16 pm 
Fouracesswe wrote:
Thanks Mark your great!


:oops: Deary me!!! Thanks but make sure you look around the whole forum and you'll find a whole wealth of knowledge! :P

Mark


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