Digital lens Coverage

No sweat phil.. I still can't find my own explanation on this back in the archives...

But in short.

There is no increase in magnification.. there is only a decrese in angle of view.

Any perceived increase in magnification is only created when we print, because we will be printing the "cropped" image at full size.. as opposed to a cropped size.

If you were to print all your images to formats that took into account the 1.6... (ie smaller peices of photo paper) then you would have images identical to a cropped area of a 35mm print.

So when someone says 20mm on a 1.6 = 32mm ... they are not saying that the lens is longer.. they are saying your resulting image will have the "Angle of view" of a 32mm lens on a 35mm film negative. (even if they don't know it when they say it)

I agree with Scotte!
IMHO None of it matters a hoot unless you have spent years working with 35mm film systems. If you have not.. or can simply forget about 35mm film.. then you can simply establish your own reference point with the equipment you use and ignore the 35mm film legacy.

The frustration level that this simple phenomenon seems to cause is what interests me.

The reason for the compilation of all these "X-Factor" threads is not only to have an answer when somone asks ready made.. (albiet that is a large part of the reason it was compiled) ...but also as a study of how on this issue it seems rare that any two minds will think alike!

Every ones seems to require a different ndividual frame of reference to which the matter must be appied.

It is a very odd thing indeed.

Until the resolution of the sensors exceeds the optical resolution of the lens, I think it's fair to say the crop is in fact increasing the magnification of the lens.

Everything else being equal, a 320mm lens on an 8MP full frame sensor will be pixel for pixel the same as a 200mm lens on an 8MP 1.6x sensor camera, assuming everything else about the cameras were the same of course. So, isn't that in fact increasing the magnification of a 200mm lens to 320mm, same as if you had a 1.6x extender on there (assuming there was a 1.6x extender of course)?

No that was my point. Increased magnification means it will pull a subject from further out in close. 200mm pulls 200 mm weither on a 35 mm or a digital 1.6 factor. It is the perception of magnification.

I have a question that relates to this dilemma... it's about perspective.

I've tried to search this forum with keywords "crop factor perspective", but I haven't really found the answer.

Let's say our beloved Canon 50 mm lenses are called "normal" or natural perspective lenses. Items further away look further away as your eye sees them in nature.

I read somewhere that what is called a normal lens on a particular camera depends on the size of its film format (frame size). Obviously this means the the lenses are designed for the particular frame size - and we can see this development also on digital format with the introduction of the new ultra-wide lenses.

My question: Is the picture of a 28 mm or 35mm lens on 1.6x camera equal to 50 mm on a 35mm film frame in terms of perspective?

Typical example of wide angle behaviour: a falling building when the camera is tilted to make the building fit the frame. The special character of optics of a lens doesn't change with cropping, does it?

On the other hand the crop factor cuts out some distortion or vignetting of some lenses.

Miika

Yes. It's all about field of view (FOV) which is the angle of view/perspective. a 50mm lens on a 35mm camera provides a 40 degree angle of view. A 31mm lens would provide the same 40 degree angle of view, or perspective, on a 1.6x crop camera. So, a 28mm will be a slightly wider perspective, and 35mm would be slightly narrower than a 50mm on a full frame camera.

Phili, regarding the 12mm - 17mm is only 2 feet statement, look at your own comparison pics that you took with the 10-22mm. On the house pictures, the 10mm vs 17mm shots were at least 100 feet different, and that was from only about 50 feet away. To say the difference between a 12mm and 17mm is 2 feet on either side is completely arbitrary, because that is only at 10-12 feet distance, not the typical landscape distance, which could sometimes be a mile or more, in which case you could literally pick up 1000 more feet on either side going from 17mm down to 12mm.

On a 1.6x crop camera, the angles of view are as follows:

10mm = 97 degrees
12mm = 87 degrees
17mm = 67 degrees

So, you can see, going from 12mm to 17mm you are losing almost 25% of your field of view, going from 87 degrees down to only 67 degrees. This means, if your target subject was 100 feet wide and would fit in 12mm, you would be losing about 25 feet of that picture by going up to 17mm.

I think that's why some people like myself, say that 17mm is not nearly wide enough on a 1.6x crop camera for most landscapes. Again, back to the crop factor, it's the same as a 28mm lens on a full frame camera, which was never considered a super wide lens.

In order to get 28mm of view of a film camera, you need a 17mm lens on a 20D/Drebel/10D, period.

Yeah, what he said.....

I like the way you were able to say in under 20 words what took me an entire page to attempt to explain.

Phil C I was on an angle if you look at the left side its slight but the right side is great that is caused by the angle of view. Perspective. If you look at the rooms its not that drastic and my comment was 12mm verses 17 mm, now if you mentally cut it half what do you have about 2 feet on either side.When you tilt a wide angle you will get a distortaion. I am only reporting how someone put the Sigma 12-24 on a tripod took 1 pic at the landscape another at 17 mm and a third at 24mm. The difference in the landscape was 2 feet on either side and that amazed me.

Now about the 28 mm lens and the 17, that is what I am debating. If I take my Eos with my 28 to 105 and view my room amd take a picture I do not get in as much as I do with my 20 d with my 17mm lens and based on crop factor its supposed to be the same.

So you can tell me its the same but I can not see where it is.

Hey you have been telling me that I have a 640mm lens and I don't, it does not pull in anything any closer, it just crops.

See thats my delema, I hear you but it does not compute?

and this statment just isnt fact (In order to get 28mm of view of a film camera, you need a 17mm lens on a 20D/Drebel/10D, period.) or I can't see where it is or did you convince me with facts. The 28mm gives the same field of view but the sensor crops it. That does not make it a 44 mm lens. Hey I am stubborn.

I am not trying to be a hard nose but I have sat back and listened and it does not compute in my book, there is someting missing.

I bought the 10 to 22 Canon which I did not like because everyone said to get wide you need 10mm, not so 17 does a good job 12 is bettrer and 10 is distorted so what good is it, I might as well buy a fish eye prime its sharper.

Anyway this is my last post as you all have answered my qiestions, thanks for the help.

The angle of view is what you get on the sensor, not what the lens is capable of covering. With the smaller sensor of the 10D/20D, a shorter f.l. lens will provide the same angular coverage on the 15 x 22.5 mm sensor that a 28 will on a 35 mm 24 x 36 mm frame. If you take a 200 mm lens on an 8" x 10" view camera, is it still a 12 degree (diagonal) angle of view? Not if it's designed for 8 x 10.

Well, 17mm on a 1.6x crop is 27mm not 28mm. It doesn't sound like a lot, but the 17mm w/1.6x crop is still almost 5% wider. 3% wider to be exact. If you include the fact that these mm ratings are rounded, the 17mm could actually be 5% wider than a 28mm on a full frame camera.

Plus, you are going in circles with the 2 feet comment on your small room shots. I understand the 17mm works for you, but your comment was that you can't understand why landscape photographers say 17mm is not enough, and that is what I was explaining to you. 2 feet is only the difference at a very short range. Landscape photographers can see a half a mile width difference at times, just as you were able to fit an entire other house in from only 50 feet away. Ok, maybe your perspective was a little different, but you have to admit the width is FAR more than 2 feet.

Phil C at 10 mm yes at 12mm no. and I understand that you get more coverage angle but you cant tell me that at 10 feet there would be a 2 foot differenc but at 100 feet it would grow, I forget what mathmatics it relates to but look at this chart. Both lenses should follow the same path and maintain that bases through out the entire range. I am not sure what the angle of degree is but this chart shows what I mean.

http://www.pbase.com/i​mage/36583041/medium.j​pg

Again I am not contesting, that wider is better but the Canon 10mm is disstorted and Sigma s 12 mm is not, that 2 mm is not much and all; I am saying is 17 mm is n ot that bad if you have to settle, anyway I did n ot start this thread over this, my comments were about conversion of 35mm to digital and I have to say I half did it because not one person took the time to really read what I said but comment on something different.

Sorry to start this carma I will not voice my opinion anymore, but read your comment and look at this chart and comment to me. My statement was not outragous, it was only an obsevation on my part and I would love to have a wider lens but the Canon does not do it and Sigmas 12 - 24 has no front lens protection, so what should we buy, a 17 to 40 Canon or a 17 to 35 Tamron, nothing else left. Thats is what I am saying.

EDITED: LINK TO ANGLE OF VIEW CALCULATOR
http://www.mat.uc.pt/~​rps/photos/angles.html

lens: film AOV => 1.6x crop factor camera AOV
according to the calculator linked above

(diagonal angle of view)

14 mm (Sigma): 114.2 degrees (film) => 88.4 degrees (15.1x22.7 mm 1.6x crop)
16 mm (16-35L): 108.2 degrees (film) => 80.7
17 mm (17-40L): 104 degrees => 77.3
20 mm (20-35): 94 degrees => 68.4
24 mm: 84 => 59.1
28 mm: 75 => 51.8
35 mm: 63 => 42.5
50 mm: 46 => 30.4
85 mm: 30 degrees (@35 mm) => 18.2 degrees (@ D10,D20 etc)

Lens AOV information according to product specs.

EDIT: Snipped out bogus chit-chat. I try to be more careful for now on...

My interest is still how the 28 and 35 lenses compare to 50mm@film


Miika

Whoah, hold up a sec. It looks like you quoted all the diagonal FOVs for the 35mm, but horizontal for the 1.6x crops.

My chart shows diagonal angle of view for 1.6x EOS lenses as follows:

10mm = 108
12mm = 97
14mm = 89
17mm = 78
24mm = 59
28mm = 52

28mm prime on a full frame is 75 degrees diagonal like you said, but anything 17mm and below is wider on a 1.6x crop. And those calculations match nearly exactly to the straight mm to crop calculations I did between the 17mm on a 1.6x vs. a 28mm on a full frame, which showed the 17mm to be a little less than 5% wider than a 28mm on a full frame camera.

The angle of view figures of different lenses at some focal lengths (for film) in my posting above are directly from product specs that can be found on websites of Sigma and Canon.

MISTAKE: To get the 1.6x figures I have simply divided

Film (diagonal AOV) 104 degrees / 1.6 = 65 degrees (still diagonal).

As there is the approximately 1.6x difference between the size of film and D10 sensor (same scale horizontal, vertical and even hypotenuse (diagonal); doesn't the angle of view change with the same proportion?

EDIT: Answer to this question is: NO!

Miika