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View Full Version : Wide Angle Lenses and acheiving Uniformity/Symmetry of the Image: How to?



audioexcels
10-Mar-2008, 15:45
I have noticed some things with wide wide angle lenses such as the 47XL or even 65-75mm lenses on 4X5, and similarly, the 110XL/120SW on 8X10, and this is an image that lacks a rectilinear view. In other words, things are crooked, skies are protruding outwards, and other objects will be tilting one way or another (often inwards). I have seen people reduce this "effect", but I cannot seem to find anything with a wide wide angle that looks linear/normal (so to say), as if we would be seeing it in real life since objects on the left and right are not tilting and the ground below us does not look like an escalator into the world. As well, clouds do not get "pushed" outwards, but should be in the sky and floating (can be out in the distance, sure, but it shouldn't look like a stray/stretched cloud).

Is there a way to use wide-wide angles and acheive a rectilinear view that shows the world as being correct without stretching/tilting/and a look as if the world is going out beyond us, rather than a look that we are looking at the world as it is, but simply taking in more of the world than a longer focal length would?

Eric Woodbury
10-Mar-2008, 16:12
Rectilinear means that straight lines remain straight and as far as I know, the lenses you mention accomplish this. What you are seeing sounds like a matter of perspective. You can only control perspective by your location relative to the subject. You may control what you are seeing somewhat by selection of subject matter and its placement in the frame. Also, a center filter may improve appearances in some cases.

audioexcels
10-Mar-2008, 16:31
Rectilinear means that straight lines remain straight and as far as I know, the lenses you mention accomplish this. What you are seeing sounds like a matter of perspective. You can only control perspective by your location relative to the subject. You may control what you are seeing somewhat by selection of subject matter and its placement in the frame. Also, a center filter may improve appearances in some cases.

http://bp2.blogger.com/_48fdG46oyK8/R0DW7ujKL1I/AAAAAAAAAdk/pw56KJs06zM/s1600-h/Vet%27s+Hall.jpg

What lens was this done with? You have some fabulous shots (including the one above) in tha blog, btw.

I don't want to get OT with this topic, but with respect to use of a CF, how would this help and also, when one is using a 3X CF, don't you have to stop down the lens way past F22 or what would the aperture of F22 using a 3X CF be?

Thanks Eric.

Mark Sawyer
10-Mar-2008, 16:54
Eric is right about the "rectilinear" meaning straight lines are rendered as straight lines... But the fact of the matter is, when you get into very wide angles, straight lines aren't straight, and rectininear lenses are distorting the world back to what we expect.

Example: Take a rectangular piece of paper, and call that the frame of your photograph. Now imagine you have a lens that covers 180 degrees, and you're photographing an infinitely-long straight wall at a perpendicular angle from, say, twenty feet away. In the middle of the frame, the wall will have some given height, and be fairly straight, top and bottom. But the wall will taper to a vanishing point at the left and right edges of the frame. Try drawing that in on the paper without any curve...

Rectilinear lenses "expand the space" at the edge of the frame to get rid of that effect, but that means introducing the "stretching" effect. You can have one or the other, but you can't have both...

David A. Goldfarb
10-Mar-2008, 17:10
It's often just about the space and the effect one is after. If you don't want the "stretched" look in the corners, try a swing lens camera, like a Noblex. Some things look more natural with a view camera lens, some with a swing lens.

This looks pretty natural to my eye--

http://www.echonyc.com/~goldfarb/photo/79bb.jpg

because it's a curved space, so it doesn't look too exaggerated with a 120mm lens on 8x10".

On this one, I'm using a wide lens to take advantage of the exaggerated near/far effect--

http://www.echonyc.com/~goldfarb/photo/cclub.jpg

But note that the bridge is nice and straight--40mm lens on 6x6.

Here's another one that uses the near/far effect but doesn't seem distorted to me--

http://www.echonyc.com/~goldfarb/photo/La'ie.jpg

75mm on 4x5".

David Karp
10-Mar-2008, 17:18
The way to keep things "straight" is to keep the film plane straight, and level. Even so, things get that wide angle look.

It is a common problem photographing architecture. Once you get into wides, especially wider than 90, you run into for my lack of a better descripter, "distortion" problems.

Look at the plates in the photo you linked above. On the left edge of the front table, the plate is becoming elongated. If there was another plate closer to the left wall, it would be even more obvious. If you can keep objects away from the edges that are not obviously distorted that helps, but the distortion is still there. And also look at the tables. They seem to fall off to the left as you get closer to the camera. These are not problems with the photograph. These are issues with the lens. I have a friend who is an excellent architectural photographer. He used to say that as a rule, use the longest focal length lens you possibly can. If you have to go wide, then you will have to deal with the problems at the edges.

I like the photo by the way. This is not a critique. It is just the nature of the beast.

When photographing the landscape with a very wide lens, sometimes the distortion does not matter, because the items at the edge are not supposed to be square, or uniform. The impact is similar to those situations where you tilt the back backwards when doing landscapes to accentuate foreground objects. Those objects are not man-made, so often times the resulting distortion is not noticeable. Nevertheless, the distortion is there.

I think David's photos illustrate this also.

Eric Woodbury
10-Mar-2008, 17:18
I don't remember what lens that was taken with. Probably a 90mm on 4x5.

My comment about the CF was to imply that w/o a CF or other correction, the center will be brighter and appear closer and the edges darker and farther away. This is something the mind does for us. I don't use CFs. I believe the 3x means that is the filter factor or exposure correction.

This pic, altho too dark on my monitor (I need to fix that), was taken with a 72mm on 5x7. So was the bend in the road in the fog.

http://bp0.blogger.com/_48fdG46oyK8/RlIkeMCwXaI/AAAAAAAAABs/GX_Ir-uqvyA/s1600-h/Oak,+Big+Sur.jpg

Good luck.

RJ-
11-Mar-2008, 05:31
Is there a way to use wide-wide angles and acheive a rectilinear view that shows the world as being correct without stretching/tilting/and a look as if the world is going out beyond us, rather than a look that we are looking at the world as it is

With all respect Mike, the world always goes beyond [us] and never rests as it is.

Addressing the technical aspect of your question, the most useful technique is the application of cross-movements (i.e. shift or cross-shift, considered in the vertical and horizontal plane).

Kind regards,

RJ

John Schneider
11-Mar-2008, 08:19
Eric is right; practically every lens is indeed rectilinear, even ultrawides. To make a non-rectilinear lens, e.g., fisheye, you have to start with a different optical formula.

What you are calling distortion is rather a matter of perspective, as Eric also correctly noted. Ansel had a good description of this issue in one of his books, but basically if you view the neg (say a 4x5) at the correct distance then the perspective will be correct. With a 47XL the correct viewing distance is very close, a few inches (try this for yourself). I don't know this offhand, but I imagine this viewing distance is the rear nodal distance of the lens, or approximately the f.l.

John Schneider
12-Mar-2008, 08:26
When in doubt, look it up in Stroebel: sec. 6.14 "Wide-Angle Effect" covers the effect you mention.

jetcode
13-Mar-2008, 20:59
Just popped a Super-Symmar XL 5.6/150 on my 4x10. The wide angle is covered.

Frank Petronio
13-Mar-2008, 22:34
OMG, he just NEEDS a Cirkuit camera!!!

run!

jetcode
14-Mar-2008, 10:53
OMG, he just NEEDS a Cirkuit camera!!!

run!

Not sure if that comment was meant for me but the 150 on 4x10 is amazing on a sidewalk looking towards the buildings. I can be off the street and out of the way of pedestrians. On a 4x10 some images can take on new dimension in my eye, like in S.F. where every sidewalk is packed with some form of eye candy, minus perhaps the more mundane sections. The 150 is an amazing lens and 4x10 is slowly becoming my format of choice.

Frank Petronio
14-Mar-2008, 11:03
No, I meant it for Audioexcels, it is the large format equivalent to the Noblex and it also makes a lovely contact print....

And if he pops for a Cirkuit it'll be good for another 20-30 threads, lol.

wfwhitaker
14-Mar-2008, 12:05
I've got some spare film holders for a Cirkut I'll sell him.

John Schneider
14-Mar-2008, 13:10
Aren't those the filmholders that are reaaally long and curved? I imagine removing the darkslide would be a pain.

jb7
14-Mar-2008, 14:37
Perspective is not distorted using wides, on a flat field-
rather it is a case of capturing a view on film that it is not possible using our own eyes-

In fact, its arguable that the perception of distortion exists only as a result of our inability to image a wide field of view naturally,
in high definition, and therefore our inability to relate to the projection of the scene.

If we could see a 120 field of view,
then objects on the periphery would be stretched as they disappear out to the edges,
just as they are when we make a photograph.

Although I know this is an over-simplification, of course-

The effects can be lessened-
the earlier comments about keeping the back parallel to objects within the frame are correct, and will help minimize the effects- or at least our perception of them-
and we can choose not to put identifiable objects towards the edges of the frame-

although this takes some discipline, and is often unavoidable-

Otherwise, why would we feel the need to use these lenses in the first place?

Cylindrical projections might help to make a scene seem more natural looking,
as long as un-natural objects (straight lines) are excluded-

j

Ole Tjugen
14-Mar-2008, 14:58
It's also a question of the subject.

Some scenes look "normal" with extremem wide angle views, some don't.

Here's one that may even look more "normal" with a 90mm on 5x7" than it would with a normal lens:
http://farm2.static.flickr.com/1076/812201524_b0f83f97fe.jpg

jetcode
14-Mar-2008, 15:23
that's beautiful ole - joseph very interesting information