Focal Length and Perspective

[Don Hoey]

Morning all,

Brain has had time to refresh.

I guess that I only ever consider the change of focal length with a change in camera position. ie wide angle move closer, gives greater depth. Telephoto, move back as it compresses the scene and draws up the background.

So it is always a combination of 2 things. Camera position and focal length.

Surely if only focal length were considered then final image magnification should be taken into account as well. The crop from a 50mm lens image in comparison to that from a 150mm lens to give the same final output size, will show significant image degredation due to the increased magnification.

Don

[robski]

Morning Don

Wheres that glorious sunshine gone ??

OK Don look at it from this point of view. You can achieve exactly the same perspective using any focal lenght providing you take the shot in the required position.

If you use a telephoto and move back far enough it will give the same effect as a wide angle. Likewise if you use a wide angle and move in close enough it will give the same effect as a telephoto.

The thing is that we don't normally use a lens it that way. Think about some of the photography in wildlife where they take you into the world of an insect or use small models of buildings instead of lifesize scenery in films.

[Don Hoey]

Originally Posted by robski

Morning Don

Wheres that glorious sunshine gone ??

OK Don look at it from this point of view. You can achieve exactly the same perspective using any focal lenght providing you take the shot in the required position.

If you use a telephoto and move back far enough it will give the same effect as a wide angle. Likewise if you use a wide angle and move in close enough it will give the same effect as a telephoto.

The thing is that we don't normally use a lens it that way. Think about some of the photography in wildlife where they take you into the world of an insect or use small models of buildings instead of lifesize scenery in films.

With you on that explanation Rob.

Weather .... well, dull and rain on the way.

Like John I spent yesterday gardening as it was a great day for that ....... somethings you just have to do.

I think that when we have managed to get some pics together it is worth posting the effect of changing your lens to obtain a particular effect. I think lots of people just use the zoom function to fill the frame, without considering how focal length choice can have a significant impact on the final image.

Stephen described it well in his post 5, but as they say, a picture is worth a thousand words, and if you are new to photography this is not something that has necessary been considered.

Christines pics were a good example of the effect a telephoto can have on the background.

Just read John's post 25 ............ Mmmmmm

Don

[Saphire]

I have just run some tests with the 100-400 lens @ 100mm, 150mm, 200mm, 250mm. All were at the same F stop and speed. I can see how the background is affected by the changes in distance and focal length. I am still finding this very hard to take in.

[Adey Baker]

Originally Posted by Saphire

I can now see how the background is affected by the changes in distance and focal length.

It's only affected by the changes in the distance from the subject, not the focal length

[Saphire]

Adey can I have a brain transplant it may work better.

[Adey Baker]

Originally Posted by Saphire

Adey can I have a brain transplant it may work better.

It's ever so easy, really! (honest, Guv!). Perspective is entirely governed by viewpoint, even without a lens! The different focal lengths just 'select' part of the scene in front of you and, provided you don't move, everything will be the same relative size to each other no matter which focal length you choose.

It's impossible for a lens to alter the relative sizes of objects at different distances in the frame - only by moving yourself, either backwards or forwards, can you achieve this.

[Saphire]

I understand in a sort of way but I think I will stick to just taking photo's and if I like what I see in the viewfinder, I will take a picture and leave this side of things for people younger with fresh brains and who can understand.

[yelvertoft]

Originally Posted by Saphire

I understand in a sort of way but I think I will stick to just taking photo's and if I like what I see in the viewfinder, I will take a picture and leave this side of things for people younger with fresh brains and who can understand.

Well said Christine. I wish more people would think the same.

Duncan

[Adey Baker]

Originally Posted by Saphire

I understand in a sort of way but I think I will stick to just taking photo's and if I like what I see in the viewfinder, I will take a picture and leave this side of things for people younger with fresh brains and who can understand.

I can't argue with that - in post #16 of this thread I stated that you can check it with a zoom lens in two seconds yet I've still managed to let myself be dragged into the debate! I don't think I qualify for the 'younger' bit, though