I’ve been into photography for about 10 years now. Back in 2008 I took the step from a point and shoot up to a DSLR and bought a Canon 450D (aka the Rebel XSi). It’s been a great camera over the years, but for quite some time I have been feeling like I have outgrown it. I wanted a new camera with better low-light capabilities and all the extra options like micro focus adjustments and more megapixels to work with. Last week, I found a pretty sweet deal on a Canon 5D Mark II, so I ordered one.

Part of this upgrade was bittersweet though. For the past couple of years, my favorite lens has been the EF-S 17-55mm f2.8 IS. Though it’s not an L series lens, the image quality and sharpness is incredible. It’s just an excellent standard zoom lens for Canon crop sensor cameras. Unfortunately, with the 5D being a full frame camera, the 17-55mm simply won’t work with it.

I had to decide what to do for a new walk-around lens. I thought about going the all-primes route. I love my 50mm prime, and the image quality of primes is top-notch. But primes don’t fit my style of photography as well, so I decided to stick with the zooms. I was left with a few options. If I wanted to keep an f2.8 aperture, I could grab a 24-70mm f2.8L II, or buy the older 24-70mm f2.8L on the used market. The first version of that lens is pretty heavy. The second version is lighter, and crazy sharp, but costs over twice as much. If I decided that f4 would be a good enough aperture, then I could go for the just-announced 24-70mm f4L IS, or the 24-105mm f4L IS (which is the kit lens of the 5D Mark II). Finally, Tamron has a nice 24-70mm f2.8 VC lens, which is the only full frame lens in this zoom range that offers both a wide f2.8 aperture and image stabilization.

While the Tamron was tempting, I decided to stick with the Canon options. I also threw out the 24-70mm f2.8L II pretty quickly, because it’s well outside my budget.

That left the used 24-70mm f2.8L and the f4 zooms. Each of these lenses come with a compromise. The 24-70mm f2.8L doesn’t have IS, and is a bigger and heavier lens. I wasn’t sure I wanted to carry around that extra weight all the time. The 24-70mm f4L IS is a new lens, and is rumored to be sharper than both the others, but costs about $500 more. The 24-105mm f4L IS has the extra zoom range, but isn’t as sharp as the 24-70mm f4L IS. So I could go for speed, sharpness, or range. This is a pretty tough decision for a lot of photographers.

I decided to go for the 24-105mm f4L IS. From the reviews, it sounded to be about as sharp as the 24-70mm f2.8, while being a good amount less weight to carry around and offering more of a zoom range. That extra zoom range was a big deal to me, because often I’ll pack my 70-200mm lens while traveling, and with the extra reach of the 24-105, I might be able to leave that longer lens at home from now on.

After making my decision, I wanted to do an image comparison between the new 24-105mm lens and my current 17-55mm. So I setup a quick composition, mounted my XSi on a tripod, and started setting things up. The camera settings I decided on were JPEG images (to remove any raw processing variables), mirror lock-up enabled, triggered with a 2 second timer, and IS was disabled on both lenses. I manual focused using live view on the digit on the 1 ball and the exposure ended up being 0.5 seconds with an f4 aperture at IOS 100. These JPEGs are straight out of the camera, with the exception of the white balance. I chose the white balance settings from one of the photos in Aperture and stamped all the other photos with it so that all the images would start with the same color settings.

Test Setup

I took photos at f2.8, f4.0, 17mm, 24mm, 55mm, and 105mm. Of course both lenses weren’t capable of all those combinations, but I did every shot I could. Below I’m going to focus more on the 24mm and 55mm focal lengths, because those overlap between the two lenses.

24mm: On the 24-105mm lens, 24mm is as wide as it gets, so the 17-55mm has an advantage of not being all the way at the end of its zoom range. The 17-55mm is also stopped down at f4, giving it an even greater advantage here. So how did the 24-105mm lens do? Well, while both lenses produced similar results, the 17-55mm was a bit sharper and the 24-105mm lens produced richer colors.

17-55mm f4.0 at 21mm

55mm: Here the 17-55mm is all the way at the long end of its zoom range, while the 24-105mm lens is pretty much in the middle. The 17-55mm still has the advantage of being stopped down though. Here, the 17-55mm lens was still sharper, but not by as much as the 24mm frame. The color of the 24-105mm lens was still better, but not by as much as the 24mm frame. This comparison was probably the closest result, and I had to look pretty hard to find any difference at all between the frames.

24-105mm f4.0 at 55mm

Zooming the 24-105mm all the way out to 105mm resulted in a softer image. Some other reviews online mention the 24-105mm lens starts to get soft at around 90mm, and my 105mm shot definitely agreed with that.

How about some uneven comparisons between the two lenses? I looked at 24mm using f2.8 on the 17-55mm lens, and f4 on the 24-105mm. Here, the sharpness is about the same. If I had to pick a winner in this situation, the 17-55mm would be it, but not by much. Again, color on the 24-105mm was nicer.

Comparing the two at 55mm with the 17-55mm lens set at f2.8 and the 24-105mm lens set at f4 was the outlying result. Here the 24-105mm lens was sharper. Not by much, but it was noticeable. The 24-105 also retained its nicer color rendering.

The results were close enough (and only visible by pixel-peeping) that I don’t think I’ll notice the difference day to day with the new 24-105mm lens. But what an impressive showing by the 17-55mm. It’s just amazingly sharp, and I’ve loved using it over the past couple of years. If you’re looking for the best image quality on a standard zoom out of a crop sensor camera, you won’t find much better than the 17-55mm f2.8 IS.

What about other factors? Well the biggest difference in these two lenses is the build-quality. I didn’t take this as much into account when I originally bought the 17-55 (back then I compared it to the 24-105mm as well and decided I wanted the wider field of view). When I unpacked the 24-105mm lens earlier today, I was floored at how much more solid it felt. The zoom rings are really smooth, and the whole thing just feels really solid. I was expecting a difference between the two, but the build quality differences were much greater than I was expecting. The 24-105mm lens is also dust and weather resistant, so you’ll be in better shape if you are out in the elements with this one.

The other difference is the maximum aperture. With f2.8, the 17-55mm lens is much more flexible. It won’t play as big of a role in this switch for me though. Full frame cameras will typically be more sensitive to light because of the bigger image sensor. So I could easily bump my ISO up one stop on the 5D to get the equivalent light of the f2.8 on my 450D (and still have shots with less noise than on the 450D).

I have posted full resolution copies of all the photos to my Flickr account so you can compare them for yourself. You really can’t go wrong with either lens. They both have great image quality, one’s a little wider angle, ones a little longer, but overall their similarities far outnumber their differences.