Perspective of 150mm, 180mm, 203mm, 250mm.

[Duane Polcou]

Greetings.

I have lenses in the focal lengths 90mm (Ilex), 150mm (Symmar S), and 203 (Kodak Ektar 7.7). There is, of course, a substantial difference in perspective (i.e., angle of view) between these three lenses. I recently obtained a Fujinon 250mm f6.3, as I wanted something substantially longer than 203mm, as well. Upon comparison, the 203 and 250 are very similiar in perspective. Since I actually like the Fujinon better as it is a bit longer , it would make sense to forego the Kodak and attempt to fill the gap between the 150mm and 250 with something approximately in between. Are those among you who are familiar with a 180mm feel this will fit the bill, or is this focal length too close to 150mm to really affect a change? Thanks.

Duane
www.modelmayhem.com > Duane Polcou (blatant self promo)

[Ken Lee]

Only you can decide. $$$

If you allow for 25% cropping, there is little difference between a 150 and a 180.

Similarly, there is little difference between a 180 and 200, if you allow for a little cropping.

Same with a 300 and a 360... etc.

[Eric James]

I have a 150mm then a 240mm - unless you have a specialty lens in mind (e.g. a macro or portrait lens) I think you'll find (at least for landscapes) that bridging the 150/240 gap is hard to justify. On occasion I've wished for a 180mm, so I used the 150mm and cropped. In addition to Ken's $$$, there is kgs.

[Ron Marshall]

Only you can determine what spacing between focal lengths is appropriate for the subjects you shoot.

Personally I find that a focal length multiple of about 1.4 works well for me. I have 110, 150, 210, 300. Enough choices to suit many different subjects, but not so many that the bank is broken and I have a bigger load to carry.

I would find 180 and 240 a bit close, at a multiple of 1.33, but I'm sure that for many it would be fine. The same for 90 and 120, at a 1.33 multiple. It really comes down to personal preference.

[Jeffrey Sipress]

There is absolutely NO DIFFERENCE in perspective between those lenses, or any other lenses, for that matter. Perspective is a function of camera-to-subject distance only. Different focal lengths only give you a different angle of view. Your statement reflects one of the most widepread misconceptions in photography.

[Ken Lee]

"...difference in perspective (i.e., angle of view)..."

What Jeffrey said.

We often think that a long lens gives a "flattened" effect, and a short lens gives exaggerated sense of near/far. In fact, it is the distance that does that:

We get the flattened effect, when we stand far away, and then choose a long lens - with its narrow angle of view - to fill the frame.

Similarly, we get the exaggerated near/far effect, when we move in close, and then choose a short lens - with its wide angle of view - to fill the frame appropriately.

While your terminology may off, we all understand your question: How many lenses does one need, to adapt to the typical variety of circumstances ?

It's a matter of taste. Even if you space your lenses according to some ideal formula, you might find in practice, that one length works best for the way you see - and it might not even fit into that formula. As the old saying goes: "Man was not made for the Sabbath: the Sabbath was made for Man."

The real problem here is in trying to get it right the first time. If you allow yourself some freedom to have fun and experiment, your real problem will be over - and all that will be left, is creativity.

[Arne Croell]

Like Ron, I like an equal spacing (as a factor) between focal lengths, for me it is also 1.4 (square root of 2). In your case, the factor between 90 and 150mm is 1.67. The next step is then 250mm (150*1.67), so the 203 is not a necessity. From 250, the next would be 420 (or 400)mm.

[Struan Gray]

I use 90, 150, 240, 420 for a 1.6-and-a-bit ratio. I have other lenses (120, 210, 360), and do use them from time to time, but not if I'm having to carry them anywhere. Cropping fills the gaps well enough for me.

[walter23]

There is absolutely NO DIFFERENCE in perspective between those lenses, or any other lenses, for that matter. Perspective is a function of camera-to-subject distance only. Different focal lengths only give you a different angle of view. Your statement reflects one of the most widepread misconceptions in photography.

You're absolutely right, but it's convenient to think in terms of framing something (e.g. a building) within the confines of your film, and in that respect thinking of wide angles as giving a wide angle perspective (even if it's in reality a result of being 3 feet away from the building) and longer lenses as giving compressed perspective (because you have to move back) is perfectly legitimate.

I mean you are right, and it's good for a novice to know this, but... wide angles give a distorted wide angle perspective and long lenses give compressed perspecitve :)

[Leonard Evens]

Perspective is affected by focal length in the following way.

In general (except when getting very close to inspect detail), most people find they are comfortable if they view a print from a distance about equal to the diagonal of the print. That is the rationale for choosing the diagonal of the format to be the "normal" focal length. If you use a lens which is either shorter or longer than the normal focal length, but you still view it from that same distance, as you are likely to do, your eye won't be in the same position relative to the print that the lens was relative to the scene. If the focal length is well short of the normal focal length, you will get what is usually called wide angle distortion. For example, spherical objects at the edges of the scene will appear ellipsoidal. If you move your eye closer, so its relative position corresponds to the focal length of the lens, then the normal perspective will be restored. Similarly, if the focal length is too long, the result will be an apparent flattening of perspective, but that effect will be lessened if you get proportionately further away.

[RDKirk]

Perspective is affected by focal length in the following way.

In general (except when getting very close to inspect detail), most people find they are comfortable if they view a print from a distance about equal to the diagonal of the print. That is the rationale for choosing the diagonal of the format to be the "normal" focal length. If you use a lens which is either shorter or longer than the normal focal length, but you still view it from that same distance, as you are likely to do, your eye won't be in the same position relative to the print that the lens was relative to the scene. If the focal length is well short of the normal focal length, you will get what is usually called wide angle distortion.

Well, within certain limits. What you say is true with regard to how things look from various distances--but I'd quibble about whether that's how "normal" got its name.

Not many people commonly view a 4x5 contact print from 150mm, and people usually migrate as close to a landscape as physically possible, regardless of how large it is. Viewing distance is more factored by physical comfort and the desire to see more detail (a particular vulnerability of landscapes, because people have a limit to how much detail they want to see in a portrait).

And I would say that the format also counts in the equation (which, of course, is a factor of what "normal" is). One can't say, "All 100mm lenses produce the same perspective at the same subject distance" without factoring in the format. If you take an 8x10 contact print taken with a 150 wide-angle lens, but crop out a central 4x5 section and view it at a "normal" 15-20 inches...it will actually show a slight compressed effect.

Most of what we consider a "normal" focal length is based on tradition and convention: The "normal" lens for a format is that which produces "normal-looking" perspective when viewed from a "normal" distance after being enlarged to a "normal" size. Probably the most constant factor in all that is nothing more than the "normal" reading distance for the "normal" human eye...and of course that has considerable variance.

We could probably determine it more numerically: That a "normal" enlargement means, say, "20 minutes of arc," so that a single figure could represent all appropriately equivalent viewing distances and enlargement sizes. So we'd then state, "With a normal lens, perspective will appear normal in any print that covers 20 minutes of arc in the human angle of view."

[Leonard Evens]

RD,

I don't dispute what you say. Many things determine how a print looks in addition to the focal length of the taking lens. But the focal length is one of them because of the reason I gave. If you define perspective purely in terms of what lines up with what in the picture, then it is fair to say that perspective is determined purely by the position of the lens. But I think most people mean something a bit more general than that by the term.

With respect to viewing 4 x 5 prints, you are right that people normally don't view them at 6 inches which would be the diagonal of the print. Few people past childhood can focus that clse up unless they are nearsighted. So you would normally be viewing such a print from closer to 12 inches, which would yield a compression effect, although it might not be too noticeable. For prints 8 x 10 or larger, I do think the general principle I stated does apply.

[Jeffrey Sipress]

Perspective is defined as the spatial relationship of objects in an image of a scene. That relationship only changes with camera-to-subject distance. It doesn't matter how you view a print, close, far, or stand on your head. The objects in the image will look the same, They can't move!

I am not considering special lenses that induce distortion or other effects by design.