The Magnification Factor is Dead

Long Live the Magnification Factor.

By now, many readers of this forum, particularly those who followed the ding between CDS and others re the ideal portrait lens, will have started to realise that they have been 'had on' rather nicely by Canon.

The 10D is a small format camera (wonderful, but small), and to disguise this fact some truly brilliant shmoozo at Canon came up with the brainwave to say 'No, it's not small format - IT'S A 1.6 FOCAL LENGTH MAGNIFICATION FACTOR' - so we all trot around thinking that we have a 35mm camera with some funny magnification built in that shortens the focal length of all the lenses that we are using.

To press the con home, the view through the viewfinder is presented exactly the same size as the size through an EOS3 etc. - probably by the use of a small magnification in the viewfinder optics.

Some by now will be reaching for the keyboard, ready to throw flame and hellfire at me, but before you do, let me explain--

A 50mm lens is a 50mm lens - that is, it will bring an image to a sharp focus exactly 50mm behind its primary objective lens.

When you clip a 50mm lens onto the 10D body, it brings the image to a sharp (some say sharpish) focus on the CMOS sensor surface. THERE ARE NO OTHER LENSES IN THE LIGHT PATH TO THE SENSOR. So the characteristics of the image are the characteristics of a 50mm lens - perspective, foreshortening and DOF (leaving CoC out of the discussion for the moment).

The only difference is - if we want to pretend that our little 22.7mm image is really a 35mm image, then we have to pretend that our lenses are a factor of 1.6 longer because that is the length of lens we would have had to have used on a 35mm camera to get the same content in our shot.

For those still skeptical - consider this exercise:-

Take a shot with an EOS3 on 35mm slide using a 50mm lens. Now take a scalpel and cut out a piece of the film 22.7mm x 15.1mm from the centre of the slide - that's the bit that the 10D sensor would have captured.

Now scan that piece and blow it up to any size you wish. Then tell me - What focal length lens did I use to take the image in my little 22.7 x 15.1 piece of film?

Now those amongst us that can tell a steaming pile of brown stuff when we smell it, will immediately realise that it does not matter how small you cut up the 35mm trannie, each bit was still imaged using a 50mm lens and will reflect the attributes of that 50mm lens.

If you want to go and blow up the little 22.7mm piece to 35mm and pretend that the 10D is a real 35mm camera, remember that no matter how much you blow up or shrink down an image - you NEVER CHANGE THE PERSPECTIVE or any other of the characteristics of that 50mm lens.

Me? I love the 10D and think that it is a breakthrough in performance and value. I even take my hat off to the shmoozo at Canon that dreamt up the 1.6x con - it had me thinking the smell was roses for a whole 6 weeks. But please -- a 50mm lens is a 50mm lens, and the perspective aspects which it creates stay constant no matter how big or little a piece of its focused image you choose to utilise.

So - what do you say? Can we all drop the 1.6x pretence and just accept that we have a small format camera (in a 35mm good looking body), and go back to talking about lens length selection with some degree of professional sensibility based on real lens length criteria? Or will some of you continue to give the shmoozo at Canon even more to laugh about?

Hey, you can't afford a 500mm lens? How about I sell you a clever piece of software that takes an image shot with a 50mm lens, and magnifies up the middle bit to 35mm, I could call it a 10x lens magnification factor - I'm sure some people would buy it!!!!! - hey I did!!

Derek Smith

Yeah so what's the point?

Nice one Derek,. :insert "worship" smiley here:

To whit,. any "magnification" that you percieve only occurs on the media,. just as if you cropped and blew up the image from a 35mmm film negative. The lens and camera do not alter magnification in any way.

Derek, perhaps you were taken in by the terminology when you purchased your camera.

I wasn't when I purchased my D60 about a year ago. I found that different photography people tried to explain it different ways, and the easiest way that I could understand it initially was that it "acted somewhat like a 1.6 teleconverter" was on each lens. Whenever I hear words like "somewhat" I know somebody is fudging in there. But, that over-simplification was what worked for me initially. Once I understood more of the details, I accepted reality.

I do have a 500mm lens (or, at least I own one if the Sigma repair shop gets it done). Effectively, it is 800mm. There are limitations to that thinking, but it works for me.

---Bob Gross---

So, what term works for you?

.6X field-of-view transmogrification?

1.6X reciprocal telephoto non-equivalency?

'So What' factor?

Maybe the best use of this board is for us all to put our heads together and to try to think of a term or phrase that satifies the need to accurately describe the phenomenon created by the smaller sensor without creating an air of sensor envy among those to whom such things matter.

It can be very ego-deflating to have someone point out that his sensor is bigger than yours. I don't see a great deal of harm in saying that your cropped image is equal to the field of view of a lens with a 1.6X greater focal length than his. It's all baloney, but it could avoid a fistfight.

Hello,. My name is CDS.....

...and I have small sensor.

CyberDyneSystems wrote:


Hello,. My name is CDS.....

...and I have small sensor.

ROOFL!

CyberDyneSystems wrote:


Hello,. My name is CDS.....

...and I have small sensor.

That's a good start. Now you only have 11 steps to go. Let's give CDS and his little sensor a big hand.

I try to compensate with the length of my lens.....

HTTP response: 404 | MIME changed to 'text/html' | Byte size: ZERO

Don't put your big hands any where near my small sensor!

Perspective depends only on OBJECT distance. If you take a picture of a street corner using a 24mm, 50mm, 500mm without moving your camera, you'll have the same perspective, only the magnification and hence the FOV is different.

Maybe Canon should advertise it as "0.6 crop factor" instead.

Ken

Probably a lot of people are. They just don't understand what it really means. But to perceive it as some big conspiracy by Canon is going a bit far.

Sure these cameras are really 21.875mm and not true 35's, but personally I don't care. I like shooting in the sweet-spot of all my lenses. What some consider a downside, others make that an upside.

One thing that is being proven every minute of every day is that these 1.6-factor cameras are producing some of the finest photographs on the planet.

That's what really matters.

Heck, maybe 10 years from now we will be shooting better than medium-format resolution on a much smaller sensor than what we're using now. By then sensor size may not be an issue.

Yeah well,.. Don't delude yourself,. this is just what they say to make me feel better....

I know a good therapist I could hook you up with to deal with that size issue.

Sorry folks,. I have just been laughing myself to near death here.. I hope no one is offended!