Conversion factor of a 100mm macro on Canon D60?

Iron Flatline · Feb 8, 2006

Hi.

So what would happen if I put a 100mm macro lens on a D60 - a precursor to the super-popular D20?

Does it become a 160mm macro zoom? What about the magnification factor?

markc · Feb 8, 2006

If it's a prime, it wouldn't be a zoom. A zoom lens covers a range of focal lengths. Were you thinking telephoto? If so, yes, it would be more telephoto.

You might find this useful: http://www.luminous-landscape.com/tutorials/understanding-series/dslr-mag.shtml

markc · Feb 8, 2006

What I should say is, it becomes more telephoto, but that's because it's on a smaller sensor. It's still a 100m lens. That link explains it well.

Iron Flatline · Feb 8, 2006

Doh, yes, sorry, of course it doesn't become a zoom. I meant tele.

I understand the DSLR stuff with the sensor size. I have the D60, and a 5D. What I was wondering about is the macro aspect. The lens is a macro lens - how does that play itself out on a DSLR sensor that is not full-size like my 5D?

markc · Feb 8, 2006

"Full size" is only in relation to 35mm film. Changing the sensor/film doesn't affect a macro. A 1:1 macro will show a 1cm object as 1cm on the sensor, no matter the sensor's size. The lens doesn't change in the fullest meaning. All that happens is that you crop off some of the image circle compared to 35mm film. The 1.6 factor is only a handy guide in figuring field of view.

Iron Flatline · Feb 8, 2006

The effect that I'm noticing is that it is harder to use.

The cool thing about a 100mm is that you don't have to be super-close to get the picture. With a 50mm, you're often hovering so tightly over the subject that you end up throwing a shadow over it, which means you need to control lighting more closely. With a 100mm you have the option of being further away.

However, like any telephoto, the further away you get, the more camera shake affects your ability to get a good shot. So now that it is a 160mm lens (effectively) I need a steadier hand, or a tri-pod.

Am I seeing that right? Or are you saying that a regular 100mm telephoto (not macro) doesn't get the subject much closer regardless of sensor, it simply crops the image tighter. That wasn't my understanding until now.

markc · Feb 8, 2006

They are both right. The minimum distance for the lens will be the same, so the macro effect won't change. The size of the image will be the same placed on the sensor. The change is that it will fill the sensor more, since the sensor is smaller. If the object fills the frame for the 5D, you would have to get further back for it to fill the frame of the D60. If you are looking to get the object to be as large as possible, you won't have any more distance so camera shake won't come into play. If you want to compose the object the same (w/ same field of view), then you will run into the issue you mention where camera shake will be more noticable on the D60 (since you are further away).

A lens won't "pull" any more on the D60 than it does on the 5D. It's only cropping. The effect is an illusion because you then "grow" that smaller image to be the same size as the larger one from the 5D. Take a shot with the 5D, crop it, then resize it in PS to the size of the original. It's very similar. The reason it's not actually pulling more is because the true magnification of the lens never changes, only the portion of the image circle you are looking at.