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DPChallenge Forums >> Hardware and Software >> Lenses for Canon XTi & Other APS-C Sensor Cameras
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Showing posts 1 - 11 of 11, (reverse)
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 05/27/2007 01:49:16 PM · #1
Hey all. I have a Canon XTi camera. It came with the WF-S 18-55mm f3.5-4.6 USM zoom lens, which is adequate but not stellar. I'm going on my honeymoon shortly, and it will include hot-air ballooning, whale watching, and a lot of opportunities to photograph things much further away than I can shoot with my 55mm max.

I've been reading the "Digital Photography Sourcebook" from a camera store that I usually buy from, and they go into a great bit of detail regarding the XTi, its sensor, and the lenses that go best with it.

In short:

* The XTi has an APS-C sensor, which is apparently more compact than other DSLR sensors.
* As far as Canon lenses, the XTi is designed for EF-S lenses, but can also host standard EF lenses.
* With EF-S lenses, there is a 1.6X conversion on the focal length. This translates to "the 18-55 range on my lens is more like 23-88mm would be on a standard film SLR."

There are far fewer EF-S lenses than EF lenses. However, other brand make them for APS-C sensor cameras. Sigma DC lenses, and Tamron Di-II lenses, in particular, suggest they're designed for APS-C cameras. It looks like Tokina AT-X (DX) models also call out APS-C sensors.

This leaves me with a few questions.

1) Am I to understand that a standard EX lens for my Canon (or similar lenses for 3rd party manufacturers) will not have the 1.6X difference from the 35mm focal lengths? If I get a 50-200mm zoom that is for the APS-C Sensor it would equate to an 88-320mm zoom in standard film SLRs. Does that mean that an EX zoom (non APS-C) equivalent would have to be 85-300 or would an EX 50-200 be apples to apples?

2) I did see a cheap 50mm lens in the EX list. I've thought it would be a nice thing to have, but a 30mm APS-C lens is like $500. Does 50mm EX mean it would really be a standard film SLR 50mm lens equivalent?

3) Has anyone with an APS-C camera tried non APS-C lenses? What are your thoughts?

4) Has anyone with an APS-C DSLR (better yet, with an XTi) tried any of these third-party brands? And what are your thoughts? I loved Tamron back in the day when I had a Minolta Maxxum film SLR.

Thanks,
Tim
 05/27/2007 01:55:22 PM · #2
The camera isn't designed for ef-s lenses, ef-s lenses are designed for cameras such as that.

From personal experience as of two weeks ago, I can tell you that whale-watching (being on a bouncy zodiak about 100 meters from the whales) is best captured by a 300mm telephoto with IS. My wife shot the whales with the 70-300mm Is, I shot them with the 70-200 F4 and a 1.4x TC - guess whose turned out better?

The 1.6x crop factor applies regardless of what lense you have attached. So whatever focal length you are looking at, multiply it.

Anyway, other than the whale watching, the only other lenses I ever actually used on vacation were the 10-22 and the 24-105.

Message edited by author 2007-05-27 13:58:56.
 05/27/2007 03:03:29 PM · #3
Ok well what you've read, while mostly correct, isn't quite right. EF-S lenses are what's called "short backfocus" which means the rear element will actually go inside the body and cast a smaller image circle on the sensor. The APS-C sensor is more or less the "standard" out there for digital SLRs. There are a few differences between the brands (Canon is 1.6x crop, Nikon is 1.5x, etc.) but overall, they are very similar. The "crop" means that it smaller than a full frame sensor (also available but $$) or a 35mm film frame.

So here's what it comes down to:
*APS-C sensors are in fact smaller than some DSLR sensors, but not most.
*The XTi is designed for EF lenses, but can take EF-S lenses
*You have the third one right.

To answer your questions:
1.) The 1.6x needs to be applied to ANY lens attached to the camera, not only the digital only ones.
2.)No, what you saw was the 50mm f/1.8 which is a fantastic lens for the price, get one if you can. It will be the equiv of an 80mm lens.
3.) People generally use more EF lenses than EF-S lenses. EF lenses will generally give a better image because they can take advantage of the center of the image circle. This means the outer edges of the frame, where most lenses aren't as good, is automatically "cropped" out of the image entirely, leaving only the good center portion.
4.) I have a Canon 350D, one model older than the XTi, and I have a Tamron 28-75mm f/2.8 SP lens. It's a great lens and goes for about $350.

Last but not least, for some lens advice check here.
 05/27/2007 11:29:45 PM · #4
OK, so I think I'm following. I had thought that there was *a* conversion on all DSLRs, but the sourcebook I was reading was suggesting something else as they introduced these APS-C lenses.

So I'm still a bit confused then. If there is no advantage to using an APS-C specific lens, then why would one buy one over the other?

I'll likely pick up the 50mm. However, it seems there were some 85-300mm lenses I may try (f4/5.6) that remain in my price range. Getting a 70-200 with IS or faster than f4/5.6 in my price range will be a trick.

Thanks for the help!
 05/27/2007 11:36:39 PM · #5
The advantages are that they are smaller, lighter, cheaper, and easier to make than their full frame counterparts. There is a conversion on *most* DSLRs, cameras like the Canon 5D and 1D have full frame sensors and do not have a crop factor.

Edit to add: What's your budget if you don't mind me asking?

Message edited by author 2007-05-27 23:36:59.
 05/27/2007 11:54:03 PM · #6
Along the lines of the previous comment (smaller, cheaper, easier to make), consider this: One fantastic lens for the EF-S mount is the Canon 10-22mm lens. On a full frame camera that would simply be incredible (and incredibly expensive). In an EF-S design, the lens can be made much smaller and more cheaply because it's not having to cover as big of an area in the back of the camera.

The downside is that there is still a crop factor... that 10-22mm translates to 16-35. But that is *still* an incredible range. I have a 17-35mm lens that I use on my full frame Canon 5D and love it for when I need a truly wide angle shot.
05/30/2007 07:35:06 AM · #7
Sam:

On the one hand I'd love to keep it on the cheap. Make that, with a wedding coming up, my fiancee wants me to keep it on the cheap. Certainly I'm going with a standard-speed lens instead of a F2.6 or something. I'm thinking $250 is my upper limit -- unless there are solid reasons to avoid that threshold.

That said, as I mentioned, the EX 50mm for $70-80 sounds cool!

Thx fo the continued help.
 05/30/2007 09:57:56 AM · #8
If you are on a budget then you may find that the Tamron or Sigma lenses offer you more choice within your price range than going with Canon branded stuff.
 05/30/2007 10:16:18 AM · #9
A wise person once told me that when you enter the DSLR world and begin to acquire components, you are putting together a camera system.

Back in the old days of constantly upgrading stereo equipment, another wise person once told me that your system will only sounds as good as your speakers.

So, along those lines, I would suggest that rather than buy an inexpensive lens that may fit today's budget, but you will ultimately not be happy with, that you either wait until you can afford a good lens, or you make darn sure that the "cost-effective" lens you pick up has a great rating.

I do not believe you are going to find something that you will be happy with for $250 other than the 50mm mentioned above and that lens will only fit a narrow range of your likely desired needs.

Here is a good site for reviews.
Lens Reviews
 05/30/2007 07:04:27 PM · #10
Well $250 isn't going to get you a whole lot for a "good" lens but will most likely get you an ok one. If you can up your budget to something like $350, you can grab the Tamron SP 28-75mm f/2.8 which is excellent for it's price. But for sure try and get that 50mm f/2.8 (the Canon one) for ~$70.
 05/31/2007 03:37:38 AM · #11
I have THIS 28-300mm lens from Tamron.

If you can't afford to go for a higher end lens with IS, I would highly recommend it for taking out on an adventure such as ballooning or whale watching where you may not want to be swapping your lenses about! From 28mm wide angle to 300mm tele (Mulitpied by the crop factor of course), it has great range!
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