Need clarity on the 1.6X factor

[stowheliman]

As a novice, I need some clarity on the 1.6x magnification factor for the Canon digital cameras. From what I understand, the reason a digital camara and film camera do not share the same focal multiplier is because the CCD sensor in the digital camera is a different size than the dimensions of a piece of photographic film. In fact, the ratio between the two is 1.6:1. Is that correct?

So the 1.6x factor has nothing to do with the lens and everything to do with the electronics in the camera. Right?

If I have a 100mm lens, it will zoom to 160mm on the digital camera. Is that correct?

When I look through the viewfinder in the digital camera, am I actually looking down the lens at 1x magnification or 1.6x magnification? Could you please explain?

Thanks........

[rcrobert]

I'm no expert, but I think you've got it about right. The 1.6x multiplication is due to the smaller size of the sensor compared to film. When the resulting file is converted to a normal size for 35mm, it has the effect of multiplying the focal length by 1.6.

So yes, your 100mm lens is acting like a 160mm lens as far as the picture you get. And what you see through the viewfinder matches what you get in the file. So the viewfinder optics must be corrected to make everything match in size/zoom factor.

Framing up your photo in the viewfinder is that same. The only time you need to really think about the 1.6x factor is when you are choosing lenses. If you buy a 20mm lens, the photos you get will look like a 32mm lens on a non-digital camera.

Hope this helps -- and that I didn't mess up too much!

[Canuck]

Hi!

As a novice, I need some clarity on the 1.6x magnification factor for the Canon digital cameras. From what I understand, the reason a digital camara and film camera do not share the same focal multiplier is because the CCD sensor in the digital camera is a different size than the dimensions of a piece of photographic film. In fact, the ratio between the two is 1.6:1. Is that correct?

* Yes, the CMOS sensor is smaller than a 35mm frame, so in comparison to a it, the 10D sensor crops the image (more commonly described as 1.6x zoom). Which would you rather pay, the $7000-8000 the D1S has for full frame sensor, or $1500 for the 10D? I have a 10D and it's great, and I know others can verify it.
Another way to describe it is that I have a 10D w/ 1.6x mulitiplier, and you have a regular 35mm Canon camera.
I have a 300mm lens and so you will need a 480mm lens on the 35mm to keep up with me in terms of zoom capability.

So the 1.6x factor has nothing to do with the lens and everything to do with the electronics in the camera. Right?

* Correct, a 100mm lens is a 100mm lens, it is all the electronics of the camera as described above. Correct me if I'm wrong, but you take that 100mm lens and stick it on a 35mm Canon camera, it is still a 100mm, right?

If I have a 100mm lens, it will zoom to 160mm on the digital camera. Is that correct?

* Correct again, sort of, you will probably not notice the zoom! The 100mm lens aforementioned is only effectively a 160mm on a camera with the 1.6x multiplier.
If you stick it on a D1S, or other 35mm Canon camera there is no zoom and it acts like it would on a 35mm. Again, cost makes it rather untouchable for most of us.

When I look through the viewfinder in the digital camera, am I actually looking down the lens at 1x magnification or 1.6x magnification? Could you please explain?

* You will see it as the sensor sees it, just like any other SLR, with the 1.6x magnification. It took me to swap from the 10D to the EOS 50E to understand the zoom bit. If you have a 35mm camera and the 10D and swap lenses between them taking pics of the same think. I think that will explain a lot.

Thanks........

* Any other questions? Welcome....
Cheers,
Canuck

[GenDEM]

http://luminous-landscape.com/tutorials/understanding-series/dslr-mag.shtml

[stowheliman]

You guys are great! Thanks for your prompt responses. You cleared it up for me!

[Phil Hall]

There is often confusion between "cropping" and magnification. Look up this article.


http://www.lonestardigital.com/multipler.htm

[kufel]

So, how about the rule of thumb about the shutter speed? you know - 200 mm lens, 1/200 or faster to avoid a shake. Does it become 1/320 or more? I vote no, the focal length and the size of projected image is the same. Any other educated guesses?
Thanx

[Webster]

kufel wrote:
So, how about the rule of thumb about the shutter speed? you know - 200 mm lens, 1/200 or faster to avoid a shake. Does it become 1/320 or more? I vote no, the focal length and the size of projected image is the same. Any other educated guesses?
Thanx

It's not an educated guess, but the way it is. The rule-of-thumb calling for a shutter speed that's the inverse of the focal length definately applies to the focal length multiplied by the 1.6 (or whatever) factor. The size of the image, that is the full frame, of the digital camera is smaller than that of the 35mm film camera. To get the same "projected" size the digital image needs more enlargement.

This usually does not apply to point-and-shoot cameras because they don't report the actual focal length but rather the 35mm equivalent.

[CyberDyneSystems]

Just alittle more info on this,.

FYI it really isn't the electronics of the camera that gives the 1.6X results either,. it is simply a matter of the decrease in the size of the "film plane".

Forget about the fact that the camera is digital for a second.

Imagine you have a 35mm camera. Then you decide to put in a different film from 35mm. This film is not as tall as 35mm nor are the frames as wide. Otherwise the camera functions exactly the same, but when you expose a frame on this saller film,. a portion of the image that would be exposed on a 35mm film frame is "Cropped off" on all 4 sides of the image.

In other words a smaller rectangular frame is being exposed and all the information that would have been recorded around the edges of the rectangle is missing.

The only reaon it starts to "feel" like there is any magnification (and not there isn't any magnification of the lens) is when the image is printed,. if you printed the image on a sheet of paper that was reduced in dimension from a 4"X6" print at the same ration that the film plane had been reduced, there would be no magnification at all. But as compared to a 35mm film frame,. when you print to a 4"X6" ( or any particualr size) you are in essence "blowing up" the center portion of the image when compared to a 35mm.

Oh lord,.

Did I just make any sense at all? :)

[CyberDyneSystems]

Oh yes,.

..as the "Blow up" effect is indeed magnifying the resulting print in relation to a 35mm,.. then for the 35mm rule of thumb regarding shutter speed to continue to apply,.. yes you would want to adjust your shutter speeds accordingly to the "crop factor/ratio" of your CCD/CMOS. :)

[kufel]

I just tested this concept with 85 mm focal length, freehanded pics at 1/80 and 1/125 sec looked exactly the same. Will try more after I get out of work.