What lens to give what the eye sees?

Hi,

Im wondering if there is a lens that will look the same as when I look at a scene with my naked eye. It seems that my photos always look different in my snappy shooter.

Its that what a prime lens is?

I will buy a lens to use with the 350D.

Cheers

well they say, and you know who they are, that 50mm is to a film camera, what the naked eye basically sees. That would mean for a 1.6 crop on your XT that a 32mm would be the same.

Prime is a lens with fixed focal lengths, IE non zoom.

A 50mm lens. It's the perspective of the 50mm lens that makes it close to what the human eye sees, not the length, so the crop factor doesn't come into it at all. The crop factor has been debated time and time again, though not with regard to being similar to the human eye, but the same arguments will probably come up. I'll try not to be drawn into it, I suggest that everyone gets a zoom lens and tries it for themselves before arguing theory that very few people (including myself) properly understand.

haha i see the x-factor strikes again.

a 50mm lens (in 35mm format) is considered a normal lens because it produces a field of view (FOV) that is equivalent to that of human eye's. but the FOV must take into consideration the size of the imager (be it film, or digital sensor). on a smaller sensor, the field of view is also smaller, thus rendering the 50mm lens more of a telephoto lens on the XT/20D.

like dante stated, a 32mm lens would be considered a normal lens on the XT. since canon doesn't make a 32mm lens, your choices are either the 28mm or the 35mm.

-alex

Get your self a watch and a compass so you can get to your location at the time when the sun is in the right position. No lens or filter can move the angle of sunlight that will give the best shot.

Scott

I posted this in the thread "Must haves for landscapes". How did it get here?

I guess it depends on what you mean by "what the eye sees". If you mean width wise it's one answer, if you mean with regards to compression (features, backgrounds) it's another.

hi tim... if i understand correctly, by compression, you mean perspective, i.e., the size ratio between a foreground object and a background object?

if that's the case, perspective can only been changed if you change the distance between you and the objects. if you stand still, using your eyes, or a 50mm lens, or a 200mm lens all gives you the same perspective; yes you'll get a smaller FOV with a 200mm lens, but the size ratio between a foreground object and a background object is the same as given by a 50mm or your eyes.

-alex

Yep that's what I meant.

The view of view is different from person to person. It depends on the location of your eyes relative to the curvature of your skull. If the centerline of your face was more convex and the distance between your eye is greater then the average person's (if there is such thing) then your FOV will be greater.

The other confussion that I've read in this forum is that there is speculation that a human has a FOV of 180 deg. That would only be possible if your eyeball extents out like a fish and they are closer to your ear. We can approach the 180 deg mark but only if we take into consideration that our eyes does rapid scanning. But if our eyes remain fixed in one position our eyes will be in the vacinity of the FOV of a 50mm lens relative to a 35mm camera.

The crop factor will come into play since the determination of focal length is a function of FOV. Take for instance with a zoom lens, when you zoom into an object you are in fact changing the FOV. If the FOV is the same in the viewfinder in a cropped DSLR vs a full frame DSLR then the image view will be larger then the image captured. But that is not the case, the view in the viewfinder is actually smaller then the actual view. The view finder is actually reduced to correspond with the crop factor and in the case of 20D its 0.95% of the actual FOV.

OH jeez... the 50mm lens is not what the eye sees. It's normal only because the focal length is equal to diagonal, thus making it non-wide and not a tele. When you view an 8*10 print, your eyeballs are approximately one diagonal from the sheet = approx 13 inches. Therefore everything appears normal.

Any lens can be normal. Example: If you take a picture with 28mm lens and print it as 16*20, and look at it from 13 inches, then it will also appear normal.

Or if you view something shot at 28mm 8*10 print from a distance of 7 inches.

Simple as that. 50mm is not a magic number by any means. Just an approximation of average viewing distance from the print.

All focal lengths are full frame.

By deffinition it's considered normal when the focal length of the lens is close to the diagonal of the sensor. Do the math and you'll see.
50mm is not what I see with the naked eye. ~30 is

Just so everyone is aware, Sigma just released their 30 1.4 EX lens. Something I'm going to be seriously considering in the future.

So to re-cap in a very simplistic manner:- I should buy a 32 prime lens?


What whould you all you this type of lens for?

To me, a total beginner I would think primes are a bit limiting...but I suppose Im wrong.

Simon

Buy a good zoom to start with, if you need the small increase in quality later you buy sell it and buy what you need.

This is true for the absolute field of view - that is the area that is detected by the eye, where movement or presence of an object is detected. But much of that is in the periphery, not very detailed, and not of primary focus to the eyes. The area of primary focus and clarity of the average person (it is recognized that there is a fair amount of variance) is approximated by a 50 mm lens on the 35 mm film frame.

True - probably more like 160-170 degrees. But the use of such a wide lens, when the final image is printed, will not be what your mind/eye combination sees as "normal".

I think you're on the right track, but that needs some rewording. The focal length is the focal length independent of what the lens is mounted on. It is a physical measurement between the "second principal point (or rear nodal point) of a lens to the focal point" (the point at which it achieves focus somewhere behind the lens - presumably the film or sensor). Many like to use the "equivalent focal length" relative to 35 mm film since that format is so universally familiar, but the lens doesn't change. If you're used to medium format, you'd consider a 50 mm lens as a wide angle lens.

When you zoom, you are changing the field of view. I'm not sure what you mean by "image view" though. The viewfinder is generally very close to what you'll get in a print (95% of it in the 20D, which is quite typical of viewfinders). The viewfinder is designed to match the size of the final image. The fact that it's only 95% isn't because of the smaller sensor, but because of other design constraints (like making the mirror fit behind the EF-S lens mount).

Now, you will have to zoom to 50 mm on the 20D to match the field of view of an 85 mm lens on the 1Ds or something around 65 mm on a 1D Mk II (and that's for field of view only). And if you are standing in a particular spot and want a particular framing of a particular scene with these 3 cameras, you'd have to use these 3 respective focal length lenses to do so.

The same holds true for the "standard" 50 mm lens. If you are standing in that same particular spot and have framed an image on your 1Ds with the 50 mm lens, you'll have to place a 31 mm lens on your 20D or a 38 mm lens on your 1D II to obtain the same image (frame) at the same position (perspective).

If you use a wider lens than those listed in the last paragraph, you'll either have more periphery in the image, or you'll have to change your position (point of view or perspective) to include only the original content in the image. And of course, changing that position will also change the relative positions of objects in the image (relative to each other vs. relative to you). The opposite is true of the telephoto - you'll have to move back to include everything in the frame. And by moving back, you change the ratio of distance between yourself and objects vs. objects and other objects in the image. That is what gives the wide or telephoto "look" in the first place.