Difference between 200mm and 300mm

[fingerz]

On my Sigma 70-300 the difference between the 200mm setting and the 300mm setting is negligible. The 300mm is very slightly closer but it's hard to tell the difference, at least to my eyes.

Is this a normal thing across all lenses? If so, I'm assuming the difference grows smaller still on even longer lenses, based on the fact that the difference between the 18mm end of my 18-55 and the 55mm end is quite noticable, and that's only 37mm difference, as opposed to the 100mm difference on the longer lens.

 

[Gandhi]

its all to do with the percentage dude, if you move the zoom a corresponding amount on the smaller lens you'll find the magnification is similarly negligble.

 

[fingerz]

Does that mean the 200mm setting on my Sigma would look different to a 200mm prime lens?

 

[CT]

No Jamey. 200mm is 200mm.

 

[fingerz]

Oh... So back to my original question then... Why does 100mm difference look less than 37mm difference?

 

[Marcel]

I think it's down to perspective, in that a difference of 35mm looking at something 400 yards away is going to differ from a difference of 35mm looking at something 10 foot away.

If that makes sense. Just like the difference in distance physically between two points, it seems less if the two points are further away, even though the physical distance is still the same.

 

[CT]

This could get very complicated Jamey and we had a lot of trouble with hyperfocal distance IIRC.

I'm not even going to attempt a serious technical answer to this (or imply that I could) but it's probably to do with the fact that as the focal length increases, perpective is compressed, the longer the lens, the more drastic the compression. The camera actually does lie quite signifiicantly, never more so than when using these long lenses.

The compression effect is used deliberately to good effect though in many situations, contrary to popular belief, landscape photographers wiill often use a tele lens rather than a wide angle, to isolate a particular part of a landscape, and the compression effect on distance and perspective gets them a version of the landscape which doesn't in truth really exist. There's a lot more to learning about using different focal length lenses than meets the eye - it's quite a skilful choice in some situations.

A good example of the compression effect is those television shots you see of freeway traffic in the USA particularly, where the vehicles appear all stacked up on each other with no space in between. Deliberately done with a loooooong lens to exaggerate the situation and it does look effective.

Hope that helps mate. Jamey, I'd seriously recommend getting yourself down to the local library where you'll be able to pick up an armful of good books which will answer a lot of these questions for you.

 

[fingerz]

That's sort of what I suspected. Cheers.

And sorry to offer such a short thanks for a long answer.

 

[Pink Fairy]

That's sort of what I suspected. Cheers.

And sorry to offer such a short thanks for a long answer.

It is simply percentage of increase... going from 18mm to 55mm is almost tripling the focal length, if you're at 200mm you'd need to get to 600mm to see a similar gain.

cheers,
Andy

 

[Gandhi]

It is simply percentage of increase... going from 18mm to 55mm is almost tripling the focal length, if you're at 200mm you'd need to get to 600mm to see a similar gain.

cheers,
Andy

Thats pretty much what I was trying to say in my usual oblique manner!