perspective of normal lens and eye

Hello,

I have a question about normal perspective. When using a normal lens (35mm on DX), I find it can only capture a small faction of what my eye can actually see. To capture more I need to use a wide angle, such as 12mm, but then I get wide-angle perspective which is not what I'm looking for. Can anyone show me why my normal lens can not capture all the field my eye captures while retraining the perspective? Should I go for a larger format "view camera" to get that?
Any tips?
Mark

afaik 50mm is closest to what your eye sees, but that means the feel of distance etc. but you can get the same field of view as your eye does. basically your eye is a fisheye lens. you have a full 180 degree view with your eye.

so a 50mm lens gives you a crop of what your eye sees, but with the same perspective as your eye sees that crop, but you can't get the outer part of the crop without going to a wider lens, which changes perspective. using a 50mm lens on a much bigger sensor format would get closer to what you're looking for
--
Mario

My Gallery
http://www.mg-photo.ch

Thanks for the reply. Does that mean our mind automatically defish the scene? That's very cool. Also if I move to larger sensor, then I'll get more field of view. So will I get 1.5 more view by moving to fullframe D3 with a 50mm lens compared to 35mm on DX?

The "normal" refers to normal perspective. Not field of view.

http://www.dpreview.com/learn/?/Glossary/Optical/Perspective_01.htm

Mark Twain said:

Thanks for the reply. Does that mean our mind automatically defish
the scene?

Click to expand...

yes, pretty much. your field of view is 180° (a bit less sometimes) but only the center part is really sharp, but you can see movement 90° to your viewing point

That's very cool. Also if I move to larger sensor, then

Mark Twain said:

I'll get more field of view. So will I get 1.5 more view by moving to
fullframe D3 with a 50mm lens compared to 35mm on DX?

Click to expand...

yes a 50mm keeps perspective etc but goes wider on FX
--
Mario

My Gallery
http://www.mg-photo.ch

I recall a study from several years ago where they took a group of college students (great study subjects) and placed them in goggles/glasses that inverted the view of the world. They kept them in these things for quite some time- months I believe...

As the study progressed, the participants were able to interact with the world seeing everything right-side-up.

At the end of the study, the glasses came off and everything was then upside-down for a period of time...
Pretty amazing what our brains do for us automatically.
I'll have to see if I can find more information..
--
Quinn

The field of view of the eye is far more complicated than a previous poster has suggested. The field of view of the human eye is indeed a very wide angle lens. Our field of view is something around 120 degrees. The amount of that field of view which is in focus at any one time is really very small much smaller than a 50mm lens would give. Just look at a normal book at the middle of the page and see if you can read the words at the edge without moving your eys.

So a lens gives distortion across the scene, the human gives out of focus across the scene. It's even more complicated than that so search the internet for a full explanation.

People seem to think that a modern normal lens 50mm on FX or 35mm on DX is equivalent to the normal field of view of the eye, this is because people tend to think this is the field of view which is easy to see and focus.

Actually a normal lens started off a lot wider than a 50mm lens and those of us who can remember something in the range of 35-42mm more closely represents the eye. If indeed we could ever really say that.

So on DX thats a lens of about 24-28mm
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Bluenose

Logge said:

yes a 50mm keeps perspective etc but goes wider on FX

Click to expand...

Well, if I grab a DC and set it to 50mm equivalent, then I expect to see less field compared to a 50mm on FX?

Mark Twain said:

Mark Twain said:

yes a 50mm keeps perspective etc but goes wider on FX

Click to expand...

Well, if I grab a DC and set it to 50mm equivalent, then I expect to
see less field compared to a 50mm on FX?

Click to expand...

no, using a wider lens on DX crop, gives the same field of view as a 50mm on FX, but you changed perspective by doing so.

and there is still medium format or even bigger, where 50mm gets really wide

--
Mario

My Gallery
http://www.mg-photo.ch

"no, using a wider lens on DX crop, gives the same field of view as a 50mm on FX, but you changed perspective by doing so"

Now you're confusing people.

The first part is correct (Using a wider lens will give same field of view), but perspective does NOT change based on the lens, or the crop of the camera.

Perspective is independent of the field of view (or lens) used. It is entirely dependent on the position of the lens in relation to the subject.

In other words, perspective does not change, as long as the photographer is not moving, irregardless of the lens being used.

There was a great article in Popular/or Modern Photography decades ago...late 70's/early 80's maybe. They asked about 20 different photographers to define/illustrate what focal length a normal lens should be , and got 20 different justifiable arguments for everything from a 180 deg fisheye to a 500mm tele.
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-KB-

Mark Twain said:

Hello,
I have a question about normal perspective. When using a normal lens
(35mm on DX), I find it can only capture a small faction of what my
eye can actually see. To capture more I need to use a wide angle,
such as 12mm, but then I get wide-angle perspective which is not what
I'm looking for. Can anyone show me why my normal lens can not
capture all the field my eye captures while retraining the
perspective? Should I go for a larger format "view camera" to get
that?
Any tips?
Mark

Click to expand...

.. so long time ago I dont remember the source, is that the 85 mm on a 35 mm/FF is what is most close to our eyes normal perspektive, and therefore the images has a very pleasing, natural look. I agree about that, but it is not the same on a 1.5x crop camera, and a 50 mm is not a good replacement IMO.
--
http://bonusphotography.wordpress.com/

Mark Twain said:

Hello,
I have a question about normal perspective. When using a normal lens
(35mm on DX), I find it can only capture a small faction of what my
eye can actually see. To capture more I need to use a wide angle,
such as 12mm, but then I get wide-angle perspective which is not what
I'm looking for. Can anyone show me why my normal lens can not
capture all the field my eye captures while retraining the
perspective? Should I go for a larger format "view camera" to get
that?
Any tips?
Mark

Click to expand...

Normal is relative in this case. I have analyzed this over the years and here is what I found.

On 35mm format, a (approx.) 50mm focal length captures the scale of what the human eye sees.

On 35mm format, a 28mm focal length lens captures the "perspective" or field of view of the human eye.

The rough equivalents in DX are 35mm for normal scale of the image the eye sees and 18mm for the equivalent field of vision.
gk
--
'I'm not as smart today as I will be tomorrow.'

The first is "Perspective". As a poster mentioned earlier, for a given camera to subject distance perspective doesn't change regardless of focal length. The examples on the cited page ( http://www.dpreview.com/learn/?/Glossary/Optical/Perspective_01.htm ) illustrate this pretty well.

The second is "Field of View". Again, as a previous poster indicated, for a normal person the field of view is nearly 180 degrees, but only the area central to where we are actually looking is in focus. The area to the left and right are out of focus but we can still detect motion.

The third is effective magnification. For a 35 mm camera (or "full-size", FX sensor) the area capturing the image is 36mm x 24mm. To get a magnification of "1" (not wide and not telephoto) you need the focal length of the lens to equal the diagonal measure of the capturing area. For 35mm and FX sensors, this works out to 43.27 mm. That's why most cameras started with the "normal" 50mm lens. If the pentamirror or pentaprism system that delivered the image up to your eye didn't provide additional magnification (or fraction), then when you placed the camera before your eye you'd see exactly the same magnification as with the naked eye. I guess this is partly why DPReview provides both the, "Viewfinder magnification" and "Frame coverage" values for each camera in the Specifications page. It would be kinda like a movie director holding his hands in front of his face, forming a rectangle.

For a DX sensor in the Nikon lineup, the sensor is 23.6mm x 15.8mm. The diagonal measurement is therefore 28.4mm.

So I guess the answer to your original question depends on which concept you're considering.

----------------------------------------
Mothman13
http://www.pbase.com/mothman13

Thanks for all the replies I get. Somehow I still have a maybe sily question:

Using 35mm terms, is it possible to get 28mm of the equivalent field of view and 50mm scale of the image at the same time, by using a larger senser (be it FX, medium or large format?

Mark Twain said:

Thanks for all the replies I get. Somehow I still have a maybe sily
question:
Using 35mm terms, is it possible to get 28mm of the equivalent field
of view and 50mm scale of the image at the same time, by using a
larger senser (be it FX, medium or large format?

Click to expand...

Well yes, a large format takes in more image so you get to or close to waht you are seeking. Otherwise, I think you are just talking now about a panorama shot with the "normal" lens and stich together the photos.

Plus/or, it does matter how big you enlarge. The same pic printed larger than smaller usually creates a different impression.

gk
--
'I'm not as smart today as I will be tomorrow.'

What I have read about field of view and field of vision agrees with what Mothman13 has said. If you notice, a director when framing his shot uses only one eye, not two. If you use one eye to view your subject, it should be about a 60 degree horizontal field, which is similar to a normal lens (as correctly defined by Mothman13).

Another issue is the distance at which you view your 2D captured image. I don't know the exact formula, but it seems that if you view a wide angle 2D image (print or monitor) up close, you get a similar perspective as it was taken. The inverse is also true. Thanks Mothman13 for explaining "normal lens". If you want more information, try wikipedia and search on field of vision.
--
Dave

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