APS-C lens mm are correct

[Daniel Flather]

Having a new baby keeping me up at night is clouding my thinking.


EDIT: Does CR compress photos when I attach them to a thread?  The attached photo look great on my iMac and iPad. I think my monitor at work here is getting old (it's a $199 special from day one).

[Sporgon]

Daniel, I have to admire your tenacity !

Are you sure you didn't sneak a little further back for the APS-C shot - it is a little wider framed but this might be the focal length of the lens.

If nothing else the two pictures are a good example of how the modern 85L has improved contrast control and tones over the film era 50 1.4, which tends to have more abrupt highlights - but that's another topic altogether.

I assume you are showing the toy in the APS picture is smaller in relation to the child. If you were only a foot or so further away this would explain it. However, if you were not....................maybe we can open a complete new can of worms! I'm very short sighted, and without my glasses on things that are out of focus appear much bigger than when viewed in focus if I put my glasses back on. Could it be that on a very fast lens like the 85 1.2, the out of focus element looks bigger due to the blur ? As there is less focus blur with the 50, this could explain it.

[Sporgon]

Nice example privatebydesign. I presume the lady in the photo is trying to explain this over the phone to one of the doubters.............

[KyleSTL]

Re. Perspective and focal length.

As a picture is worth a thousand words.

First comparison, 17mm lens and 200mm lens both on same camera from same place and both f8, these are the full images.

Second comparison, same images with the 17mm cropped to match the framing of the 200mm.

As you will see, whilst the dof is very different, the perspective (the size of the various elements within the frame with regards each other) stays constant. The woman, the trees and the jumps are the same size in both examples when the 17mm is cropped.

This is also a very graphic demonstration of why smaller sensors have deeper dof, the second image crop is effectively a small sensor shot with an 11 times crop factor, which still puts it way bigger than P&S's and phone cameras.

Not true, below are crop factors of various sensor sizes:

FF - 1x
APS-C (Canon) - 1.6x
m4/3 - 2x
Nikon 1 - 2.7x
1/1.7" - 4.6x
1/2.5" - 6.0x
1/3" - 7.2x
1/4" - 10.8x

I believe the iPhone sensor is in the ballpark of 1/3", for example.

[sandymandy]

I cant understand why this topic always gets discussed so much? a 50mm lens is a 50mm lens

A photo taken from the same position with a FF camera will look like it was taken with a 50mm lens. A photo taken with an APS-C will look like it was taken with an 80mm lens.

Thats all what the crop factor is about and its so easy and clear to understand, why gotta discuss so much?

Its just common to say "equivalent of blabla on APS-C". Maybe its just the wrong term used but so what? everybody knows what it supposed to mean.

[neuroanatomist]

Its just common to say "equivalent of blabla on APS-C". Maybe its just the wrong term used but so what? everybody knows what it supposed to mean.

You'd think so, but >80 posts here and many other threads on the topic suggest otherwise...

[PackLight]

Re. Perspective and focal length.

As a picture is worth a thousand words.

First comparison, 17mm lens and 200mm lens both on same camera from same place and both f8, these are the full images.

Second comparison, same images with the 17mm cropped to match the framing of the 200mm.

As you will see, whilst the dof is very different, the perspective (the size of the various elements within the frame with regards each other) stays constant. The woman, the trees and the jumps are the same size in both examples when the 17mm is cropped.

This is also a very graphic demonstration of why smaller sensors have deeper dof, the second image crop is effectively a small sensor shot with an 11 times crop factor, which still puts it way bigger than P&S's and phone cameras.

I have to disagree, your definition of perspective only relates to the size of things in the picture. Since the two pictures obviously have a different depth of field the one shot with the 200mm creates a different illusion of depth and therefore a different perspective. At best you can say the elements in the picture are the same size once cropped. You can say that the pictures were shot from the same perspective, your perspective. But the pictures do not have the same perspective.

[PackLight]

Its just common to say "equivalent of blabla on APS-C". Maybe its just the wrong term used but so what? everybody knows what it supposed to mean.

You'd think so, but >80 posts here and many other threads on the topic suggest otherwise...

What is amazing is that there are so many threads about it. Many people just use crop or ff not both. The reality of it is if  you use a crop camera and do not own a FF, the ratios and comparisons are meaningless to you. If you own a FF and do not use a crop it is meaningless to you. Yet it is important to debate what does not matter.

But then again this thread went through 3 pages of perspective talk.

[neuroanatomist]

I have to disagree, your definition of perspective only relates to the size of things in the picture. Since the two pictures obviously have a different depth of field the one shot with the 200mm creates a different illusion of depth and therefore a different perspective. At best you can say the elements in the picture are the same size once cropped. You can say that the pictures were shot from the same perspective, your perspective. But the pictures do not have the same perspective.

Sorry, no. It's not his definition of perspective, it's THE definition of perspective.

perspective
|pərˈspektiv|
Noun
1. the appearance of things relative to one another as determined by their distance from the viewer

The fact that the objects in both images are the same size in relation to each other means the perspective is identical, by definition.  DoF has nothing to do with it, relative blur has nothing to do with it.

But then again this thread went through 3 pages of perspective talk.

...and with apologies, unfortunately it seems the point is still not clear to some. 

[ahab1372]

And while we are at it: compression is also not a feature of the lens, but of the distance. It is actually included in Neuro's  THE definition of perspective.
If you are farther away, faces look flatter, no matter what lens you use.

[TexPhoto]

And while we are at it: compression is also not a feature of the lens, but of the distance. It is actually included in Neuro's I mean THE definition of perspective.
If you are father away, faces look flatter, no matter what lens you use.

Yes!  You don't even need a lens.  This effect can be seen with your eyes.  Close one eye and put the other an inch from someones nose.  (Maybe make sure this is  a friend).  Wow huge nose, fisheye perspective! 

[PackLight]

Sorry, no. It's not his definition of perspective, it's THE definition of perspective.

How would this definition not apply, this is from a simple google search of perspective (it appears at the top);

"The art of drawing solid objects on a two-dimensional surface so as to give the right impression of their height, width, depth, and...
A picture drawn in such a way, esp. one appearing to enlarge or extend the actual space, or to give the effect of distance."

Granted we are not drawing in the literal sense of the word, but we are creating the image. Is our work "art" or are we just capturing an image relative to the viewer.

Personally if we are using the perspective as it relates to the content of the picture itself, I prefer this definition as it adds the element of depth.

This one is from the Free Farlex Dictionary online;
"4. The technique of representing three-dimensional objects and depth relationships on a two-dimensional surface."

[PackLight]

...and with apologies, unfortunately it seems the point is still not clear to some. 

Crystal clear, I am just disagreeing with how we are using the word "perspective"
I think in a hobby we strive to create something that is considered art, we should use the definition that closely matches the one for art. 

[neuroanatomist]

I suppose I should have indicated that's THE definition for photographic imagery.

The point of the definitions that pertain to drawing (which are the definitions you reference) is that for proper perspective, the size relationships of the rendered objects must be appropriate to one another and relative to the distance at which they are apparently rendered, so that 3D space is correctly represented as 2D. With a photograph, that's already a given due to the direct capture of the image, which faithfully preserves spatial relationships at the distance from which the image is captured, so those definitions are irrelevant to photography. I'm not arguing that photography isn't art, but the definitions you reference aren't any more relevant to a photographic image than they are to music as an art form.

You can choose to believe differently, and I'm sure many will agree. But then, many people think alot is a word, and that doesn't make it correct.

[PackLight]

From photonotes.org
Dictionary of Film and Digital Photography;

"Perspective.

Visual cues in a two-dimensional image which give the impression of three-dimensional space. Such cues include lines converging towards a vanishing point, aerial haze, different sizes of common objects, different zones of focus, etc."

I suppose there are alot of people that think this way.