True Macro Zooming Lens? + zooming and manual focus while tethered?

Question

This is a follow up to a few other recent questions about shooting artwork including: macro lens for artwork with the T2i

I just received my T2i and tethered it to my laptop. With the stock lens it seems I can Auto Focus, and basically set up and take the pictures, all tethered the laptop. I'm very pleased!

1. Can I manually focus from the laptop (I wasn't sure how but sometimes that wil be needed)?
2. What is the advantage that a USM lens would offer? Or is USM what I need to manually focus tethered?

3. It seems like I should go with one of these three lens:

   1. Canon EF-S 60mm f/2.8 Macro USM
   2. Canon EF 50mm f/2.5 Compact Macro USM Lens, or
   3. Canon EF 50mm f/2.5 Compact Macro Lens (non USM)

4. The T2i says it is "EF-S". Can I only use these lenses or are the EF ok too?

The compact macro lens don't offer true 1/1 but they are cheaper and still remain distortion free. (as least that what I'm given to understand?)

5. But I was also wondering if there is a zoom lens that will offer a low distortion result? (Primarily the problem with artwork is the bending around the edges.)

With about 1000 works to shoot I reckon it will be a lot easier If I didn have to reposition the camera for every shot. I'm hoping maybe to be able to zoom a little (not much) to each subject to make it fit nicely for full resolution. And if I can zoom and manually focus from the laptop it will obviously save a fair amount of effort. My primarily concern therefore will be making sure the subject is centered on the stand. And then I'll only have to move the camera when when I have a significant change in subject size.

I hope this makes sense! Maybe I don't need USM? Maybe zooming isn't possible tethered? Or maybe it is possible but will have too much distortion?

Also, I do have some room, up to 10' from camera to subject. And the largest artwork I'm shooting is only 30"x40" (average is probably 18"x24"). Is there any advantage to going with a 100mm Macro Lens instead of the 50mm or 60mm?

Answer 1

Your camera is built for EF-S lenses, but EF lenses will work just fine. It's going the other way (trying to use EF-S lenses on a full-frame EF-mount camera) that's fraught with danger. And unless you are shooting things that are less than three inches on the longest side, a 1:2 "half-macro" lens will work just fine.

The reason we kept hammering on about using a macro lens is because they are usually very good at making sure that rectangles remain rectangles -- they are corrected for rectilinearity, and usually don't have barrel (bulging) or pincushion (pinching) distortion that you can find without really accurate measuring devices. Zooms almost always have one or the other kind of distortion (and often both, one at each end of the zoom range). If you're taking pictures of "stuff" in the real world, you don't often notice a small amount of barrel or pincushion distortion, but when you are shooting rectangles it'll be apparent.

Macros also tend to have very flat planes of focus (I mentioned that before) so you can set the aperture for the best sharpness the lens can offer and don't have to worry about depth of field. (With some lenses, you'd need to focus so that a circle of the artwork about 1/3 to 1/2 of the way out from the center is in sharp focus, then stop the lens down until the center and the corners appear to be in focus as well.)

A zoom lens that is both well-corrected for geometric distortion and has a very flat field is going to be pricey (and price alone is no guarantee -- read any technical lens reviews you can find online). A good fixed-length (prime) lens is going to be a lot easier to find at a digestible price point.

If you are not shooting the works in situ, then a copy table/stand will help a lot with the workflow. A commercial copy stand can be expensive, but if you're handy at all (or know somebody who is) then building a version that is better than what's commercially available isn't too terribly difficult or expensive. I can send you plans for one if you email me (put a period between my first and last names and send it to Gmail).

<aside>I really need to post some of the DIY stuff I've created on a website sometime. When you build the stuff that you can build, you can save many thousands of dollars. I figure that I paid for my RZ67 and a couple of lenses with money I didn't spend on other gear.</aside>

Answer 2

I can't answer everything, but... numerically:

1. Manual focus, by definition, is by turning the ring on the lens. So, I suspect you're actually asking if you can autofocus using software or fine-tune that focus. You can make focus adjustments tethered, but it's not enormous, it will depend a lot on subject distance and the lens.

2. USM is lens driven focus using what Canon calls an ultra sonic motor. It's usually faster and quieter, but I doubt it would matter much to tethered control of the adjustment. Does matter if you want to manually adjust on the lens since it allows full-time manual control in AF.

In terms of the remainder of this rather exhaustive question, I don't think you can control of the zoom via software. I'm not aware of any lens that doesn't require physical adjustment to zoom. Having said that, a lens that gives you a range is going to be handy for varying art sizes, so it's a consideration. On the other hand, primes are usually sharper. In any case, Canon makes pro level zooms, with pro level quality, and a pro level price. That may still be a lot cheaper than a collection of primes in the same range and the minor quality trade-off may be such to make that call probably likely.

For the rest, I'll leave to the Canon experts... Or they can dispute my post as well. :)

Answer 3

I think you will be better off by cropping the macro shots a bit than using a zoom. No zoom is going to be anywhere near a macro prime when it comes to lack of distortion and optical nasties.