last zoom question

[Poider]

Ok one last question on the subject of zoom,
I Understand the 2x zoom and 3.2 x zoom bit now and I am over that. I know that the zoom number is only the difference between the lower and higher range.

On my D3100 if I use an AF-S NIKKOR 28-300mm f/3.5-5.6G ED VR
and an AF-S VR Zoom-Nikkor 70-300mm f/4.5-5.6G IF-ED

Would the picture taken with each lens at it's maximum zoom be the same closeness wise, I understand the difference between DX and FX, VR and non VR, full frame and cropped frame, smaller aperture numbers on lens means larger apertures and faster shutter speeds equalling the ability to shoot in lower light.
I know I have a long way to go but I am learning ever so slowly.
I am stil not sure exactly what 28 mm refers to or 300 refers to but as I say I am getting there.
Peter

[RichardTaylor]

The answer is yes.

[Poider]

Thank you Richard.
So what does the 28 or the 300 stand for?
sorry another question!!

[Cold]

It is your focal length, which, so long as its on the same body, should be consistent across all lenses.

[Shokinen]

aaahhh focal lenght... what a weird concept for new photographers. Don't worry Poider, we all went through it !

The focal lenght is a concept that is not logical like ISO or Shutterspeed. It's logical when you understand the physic behind the concept, but doesn't gives you much tool on the field.

Bacially, if you choose a lenses with a small "mm" number, you should fit more in your frame, therefore you subject will look smaller. On the other hand, your subject will appear bigger with longuer focal lenght.

Now, that was the easy part. If you choose for example 200mm and you take a shot. Now, try something like 85mm and get closer to your subject to get approximalty the same picture. Don't change anything especially Aperture. Compare the 2 picture and notice the difference in the background. That's call compression and it increase with longuer focal lenght.

Choosing the right focal lenght for want you want to acheive takes time. Knowing what you want to acheive in advance takes time. Photography takes time. My point is focal lenght do not only affect how close you subject appear in your viewfinder. They affect the distortion and the compression of an image - And it takes time and practice to get used to it and understand the effect they have on images, so be patient.

Do some research on google / wikipedia for the theory behind it. There is many good explanintion aroun (much better than mine hahaha).

Hope this helps

[Aegea]

The focal length is an inherent physical attribute of the lens. If you had say a 100mm simple lens (just a piece of curved glass, none of the multi-element complexity of most camera lenses) then the focused image of a distant distant object would be 100mm behind the lens.

(If you ever set pieces of paper on fire or - horrors! - fried bugs as a kid by using a magnifying glass to concentrate the sun's rays, then the focal length of that lens was the distance from the lens to the poor smoldering bug.)

See: Focal length - Wikipedia, the free encyclopedia

[Michael_2010]

Did you get any good pictures of those burning bugs?

[Aegea]

Originally Posted by Michael_2010

Did you get any good pictures of those burning bugs?

No, I didn't have a macro lens at the time.

[Poider]

Ok now I understand the number side of it, if a lens is 18mm - 200mm then the main 'glass' is 18mm away from the censor at its widest focus and 200mm away from the censor at it's most zoomed.
So it's not as easy as moving any lens closer or further from the censor, a lens has a set focal length and can only focus at that point, Or for a zoom lens it focuses between the two focal points.
If aperture was logical it would be easy
large number = large hole is logical
large number = small hole is illogical
Thank you all for your patience, I am learning.
Peter

[IABoomer]

Aperture is logical when you realize that the f/number means the aperture size is focal length/number units in diameter. Thus, larger numbers mean smaller fractions and thus smaller aperture openings.

f/4 = 1/4 the focal length
f/8 = 1/8 the focal length

1/8 < 1/4, thus f/8 is a smaller opening.