amfoto1 Loc: San Jose, Calif. USA

This is far too little info to give you very good advice.

If your only lens with the 40D is the 50mm, then what you have is a short telephoto, non-macro lens with a reasonably large aperture that gives potential for relatively shallow depth of field effects.

Maybe that's all you need. Or, maybe not.

There are lots of things to consider when choosing a lens or kit of lenses. Size, weight, cost, sharpness, distortions & corrections, color rendition, autofocus performance, image stabilization... and more. Also filter size; lens hood shape, size & effectiveness; plus the shape of and number of blades in the aperture which effect how blur effects are rendered... and more. Would a zoom lens be desirable for its versatility or is a smaller, less expensive prime with a larger max lens aperture preferable? In your case, based upon what little info you've given us, close focusing ability appears to be important.

Some "general purpose, walk-around" possibilities...

Canon EF 24-70mm f/4L IS USM ($849) is a premium quality zoom with a range of focal lengths that on a 40D will give slightly wide angle to short telephoto. It's also exceptionally close focusing for a zoom lens.... able to render .70X magnification, which is 2X to 3X higher magnification than any other mid-range zoom offers. It's also got image stabilization and high performance "USM" (ultrasonic motor) focus drive that's fast and reasonably quiet. This lens is very well corrected with top image quality is full frame capable (40D can use both full frame "EF" lenses and crop-only "EF-S" lenses, equally well).

Canon EF-S 17-55mm f/2.8 IS USM ($549) is a crop-only lens with moderate wide angle through short telephoto range of focal lengths AND a large-for-a-zoom f/2.8 aperture AND image stabilization AND with high performance USM focus drive. It is limited to use on crop sensor cameras such as your 40D and is well corrected with excellent image quality. It's currently on sale with the largest discount I've ever seen offered, $330 off the usual price, which suggests to me that Canon may have a new version coming in the not-too-distant future and is clearing the shelves (this is pure speculation on my part). BTW: Early examples of this lens, which was introduced in 2006, had some issues with dust getting under the front element over time. That was pretty easily solved, but there were quite a few posts about it online years ago. I haven't seen any of those complaints in recent years, so I have to assume that Canon made some changes and has been sealing it better to keep dust out. If buying a new one, I wouldn't worry. But if buying a used one, this might be a consideration.

Canon EF-S 15-85mm f/3.5-5.6 IS USM ($799) is another crop-only lens, this time both wider and longer than the above, but with smaller max aperture and a variable aperture. Still, with excellent image quality, good build quality, high performance USM focus drive and image stabilization it offers a lot of versatility in a "walk-around" zoom. Someone with one or two fast primes (such as your 50mm f/1.8) might have no problem with a "slower" zoom such as this. If they need their speed for low light or shallow depth of field effects, they can always switch to one of those primes, while using the zoom for most everything else.

Canon EF-S 18-55mm f/4-5.6 IS STM ($249 or less) is a budget crop-only lens that's often sold in kit with the various Canon APS-C models, but widely available separately as well. There are actually five or six versions of this lens... all of which are fairly lightly built (a bit "plasticky"), but reasonably capable. The f/4-5.6 "STM" or "stepper motor focus drive" version is the latest and probably offers the best image quality, which is pretty good for a kit lens. STM focus drive is reasonably quick, very quiet and smooth (ideal for video), though not as fast as USM. Both STM and USM are superior to noisier, slower and less consistent "micro motor" focus drive used on the least expensive Canon lenses, which includes several cheaper versions of the EF-S 18-55mm. A Canon micro motor focus drive lens simply doesn't have "STM" or "USM" imprinted on it somewhere. That may be the only way to distinguish them, in the cases where a lens is offered in several versions.

Canon EF-S 18-135mm f/3.5-5.6 IS USM ($599 or less) is another crop-only "kit" lens currently offered with some of the more advanced cameras (80D and 7D Mark II), as an upgrade option with some other models (77D and Rebel T7i), plus is widely available to purchase separately. Similar to the cheaper 18-55mm, there are several versions of EF-S 18-135mm. The USM is the most recent introduction, uses Canon's new "Nano USM" focus drive (useful both for fast action and for video) that they claim makes it 2X to 4X faster focusing than the STM version. The USM and STM versions appear to be optically identical and both have image stabilization and the same variable aperture range. The USM lens is unique in that it's the only Canon lens currently that can optionally be fitted with their PZ-E1 Power Zoom module (about $100), which might be a useful accessory for videography. There is also a usually less expensive "II" version that's neither STM nor USM and uses an older optical formula with not quite as good image quality. These zooms all offer a very versatile range of focal lengths all-in-one, though with a bit larger size, higher price, and a variable/limited max aperture.

By no means are those your only options. There are many other possibilities... Canon themselves makes about 90 lenses that can be used directly on your 40D. In addition there are probably at least a hundred more lenses made to fit and work on it, by other "third party" manufacturers (such as Sigma, Tamron, Tokina, etc.)

Aside from the 24-70mm "L" mentioned, none of the above are particularly close focusing. About the best any of them can do is around 0.30X or one third life size. However, ANY lens can be made to focus closer and render higher magnification simply by adding one or more Macro Extension Rings between the lens and the camera. Those can even be used with the EF 50mm f/1.8 lens you already have, to make it much closer focusing. (Note: Older extension tubes did not accommodate the modified mount Canon EF-S lenses... but I am pretty certain any produced the past 5 or 6 years are compatible with them as well.)

About the best deal for those are the Kenko Macro Extension Tube set, which includes 12mm, 20mm and 36mm sizes for approx. $130. They are high quality at a reasonable price. Canon themselves sell very similar high quality tubes, but only individually in two sizes: 12mm and 25mm. A single Canon 25mm tube costs more than the Kenko set of three. There are cheaper tubes ($75 or less) from other manufacturers such as Vello, but they are more plasticky and have less secure latching mechanisms. There are also extremely cheap (under $25) "dumb" extension tubes that lack any of the electronic connectivity for autofocus, image stabilization or aperture control. Because of this, I recommend avoiding them for use with any modern electronically controlled lens. You can get by without IS and AF, but need to be able to control the lens aperture! (Those really cheap tubes work fine with vintage, manual focus lenses that have a mechanical aperture control built into the lens itself... But not with modern lenses.)

There have been some suggestions about macro lenses you might consider. They certainly are faster and easier to work with than non-macro lenses combined with extension tubes. Most macro lenses also have extremely high image quality. They are optimized for close focusing, while non-macro lenses made to focus closer with extension tubes are not and may be "soft" in the corners of images (not necessarily a bad thing... it can even be useful at times).

Personally I have a number of lenses I use for close-up work and have to say, once again, whether you need one and which one might be best for you really depends upon what you're photographing. For general purpose "walk around" macro lens I generally recommend something in the 90mm, 100mm or 105mm focal length. That's a good combo of working distance and hand-holdability. My most used macro lens is a Canon 100mm. Canon offers two excellent 100mm macro lenses... I use the cheaper one without IS and it serves fine because, more often than not, when I'm out shooting close ups with it I'm using a tripod or at least a monopod. Something unique and very useful with the two Canon 100mm is that they both can optionally be fitted with a tripod mounting ring.

But, again, which macro you choose depends upon what you're shooting. If you are indoors working with controlled lighting and some sort of tabletop studio setup, I'd recommend a shorter focal length. Personally, with crop cameras like your 40D I use a Canon TS-E 45mm f/2.8 "Tilt Shift" lens. This is a specialized type of manual focus lens with "movements" that can be used to correct perspective and/or control the plane of focus. I like the shorter focal length because it puts me close enough to reach out and adjust a small subject while looking at it through the camera's viewfinder. Because I'm using controlled lighting, I don't have worries about throwing a shadow on the subject. And because it's usually small products I'm shooting, I don't have to worry about getting too close to a shy subject. Both of those might be a concern out in the field with your camera, hence the need for longer focal lengths. (Note: Canon no longer makes the TS-E 45mm... In the last year or two they've replaced it with an even closer focusing TS-E 50mm f/2.8 Macro, capable of 1:2 or half life size on it's own... I have to use macro extension tubes with the 45mm lens to get that much magnification. Canon also offers TS-E 90mm f/2.8 Macro and TS-E 135mm f/4 Macro lenses, as well as 17mm and 24mm TS-E lenses that probably would be less useful for close-ups, although they are also capable of it.)

At the other extreme, for especially shy and/or dangerous critters I use 180mm macro lens or even longer focal length. These lenses are much harder to hold steady and at high magnifications can render extremely shallow depth of field... These factors make them slower to work with and more challenging in some ways. They almost always need to be used on a tripod... or at least a monopod.

A compact, versatile macro lens I carry a lot for use with APS-C cameras similar to your 40D is a Tamron SP 60mm f/2. It takes the place of three other lenses in my camera bag, saving space and lightening the load... It serves for macro (it can do full 1:1 magnification), plus take the place of two fast aperture "portrait" lenses... a 50mm f/1.4 and an 85mm f/1.8, in my case. The 60mm f/2 has a stop larger aperture than most macro lenses... making it more useful for some things, such as portraiture. Granted, it's a stop slower than my 50mm, but I usually stopped that lens down to around f/2 or smaller anyway. Compared to the 85mm, the 60mm macro is only 1/3 stop slower. The only shortcoming of the Tamron 60mm lens is that it uses a micro motor focus drive that's pretty slow. It's fine for portraits and macro... but too slow focusing for any sort of sports/wildlife action photography.

What works for me might or might not work for you. I've tried to be more detailed than just saying "I use X lens and it's great".

If you have other interests, very different lenses might be better choices. Above I've only covered a few versatile "walk around" zooms and some info about close-ups with extension tubes and macro lenses. Hope this helps, but we'd need quite a bit more input from you before we could make further recommendations.

As a Canon shooter, I'd highly recommend you check out the-digital-picture.com website. Bryan Carnathan has thoroughly tested and reviewed virtually every Canon lens made the last 30 years, as well as many from other manufacturers. There you also can look the specifications in detail, compare image quality of any two lenses side by side at various settings, and much more. That site is a valuable resource, most especially for any Canon user.

Photocraig

That is my lens line-up along with an EF-S 10-18. The Sigma is excellent and focuses really close for great close up detail shots.. For true 1:1 Macro I have a 90mm Tamron f2.8 Macro. An excellent lens with true flat field projection (focus doesn't fall off in the corners) and a great FF portrait lens. I've even shot indoor sports with it because the reach on the 1.6 crop gives me 144mm reach. The 2.8 allowed me to keep within the limited High ISO results (without noise) of my old 50D. Other lenses like my 70-300 f4-5.6, at any ISO over 1600 had my team looking like they had chicken pox, from the noise.

The new 70-300 II version is much better than the original for silent and fast focus and even better IS. And the price is down. It is a winner. BUT, the poor low light abilities of the older EOS Digital bodies render slower glass less useful in even moderately low light.
C

dragonlady9947

100 mm is a great lens-good buy in my opinion.

cbtsam Loc: Monkton, MD

I'm a Nikon guy, but my experience might be relevant. For many years, the only lens I had was an 85mm 1.8. Then somebody introduced me to extension tubes, and I became a macro maniac; that was in, 1964 or so, and I haven't recovered from that infection yet.

So, I'd say that you can do well with the extension tubes for a long while, but eventually you'll want a macro lens for the convenience it offers. I've used a 105mm since before I went digital, and I've never experienced the need for a longer lens that so many talk about, but then I've never been interested in shooting macro with dangerous animals.

burkphoto Loc: High Point, NC

Personally, I’d want two or three zooms and a macro. But WHICH zooms and WHICH macro leads me to ask:

What do you want/need to photograph? Without knowing that, I can’t give you the most helpful answer.

ThornleyD

I have the canon mpe- 60, 100L and 180L macros and find all to be great but each has its own niche. The mep 60 only allows macro work and does not focus (move camera to focus) but allows up to five time lifesized, the 100mm is great and makes for a very sharp 100 mm lens, the 180mm is also great but is somewhat of a beast & requires a tripod to get sharp macro images but does give more working distance.

That said, if I was a new macro user, I would get the Canon 100 mm macros for ease of use and overall performance and multiple uses.

Scruples Loc: Brooklyn, New York

Sounds like you are on point here. Lenses are like tree leaves. They are so many, many are so different and ultimately will be replaced by another leaf.
I have a suggestion for you. Before investing a boatload of cash on a lens because someone recommended it, try renting it for a short time. Put it through its paces. If you like the photographs, buy one. If you don't like the results you wasted a small amount of memory card space and you got some useable knowledge. The specs that are published by the lens manufacturer are hard to read and understand anyway.

wdj Loc: NE NORTH CAROLINA

I strongly recommend the Canon EF-S 17-55mm f/2.8 IS USM. I used one on a 50D for years and it produced some truly excellent images. It is a great walk-around lens and is reasonably good in low light. I succumbed to GAS several years back and ventured into the full frame world with a 6-D and subsequently a 5D m4.