Points in Focus Photography

On Canon Rumors on Canon’s new 24-70mm f/4L IS USM


Today Canon announced two new lenses, an EF 35mm f/2 IS and an EF 24-70mm f/4L IS USM zoom. In many ways, both will no doubt have their controversies. It’s not unexpected, then, to see people start voicing their opinions on the lenses, and Canon rumors is right there with their opinion (and no so am I).

If you’re interested, you can read the entirety of the CR opinion piece here. I’ve quoted the few points that I feel have warranted a direct response.

First, I’d like to mention that the new EF 24-70 f/4L IS may be longer at the 70mm end then the model suggests. Lets wait and see if it’s actually 70mm, as it could be significantly longer. “24-70″ has appeal from a marketing standpoint, as it’s a highly desired focal range. If you look at the EF 70-200 f/4L IS, it’s actually quite a bit longer at the “70mm” end. [emphasis mine]

Before I go on, let me just say, I would put the odds of Canon deliberately mislabeling the focal lengths on this lens to the scale that this comment makes any sense, to be somewhere between none and zero.

I’ve included the whole paragraph for context, even though I’m really only interested in the bolded portion, the assertion is that the 70-200 f/4L IS has a focal length considerably different than it should be. I have to admit, I was struck somewhat odd by the idea that Canon should or would deviate from the standard practice in labeling lenses, or that we should expect that they might.

The nice thing about so much in photography is that much of it is testable. In fact testing things has, in my opinion, gotten a bit out of control, sometimes to the point that many photographers forget that their job is to make evocative images, not peep at pixels.

Now I want, rather badly actually to simply say that statement is untrue and move along. It would certainly save a lot of work, but that would also leave me a statement that’s just as unsupported as the one I’m trying to examine.

Fortunately, it’s actually not hard to approximate the focal length of a lens; you merely need a wall, a tape measure, and some trigonometry. Obviously, this isn’t as good as a serious engineering measurement approach but it’s sufficient to get at least an idea as to whether the claim is plausible or not.

The 70-200/4 IS is an internal focus lens, which means the indicated focal length is only correct when the lens is focused at infinity. As the focus is racked closer to the lens, the focal length contracts as a byproduct of movements made by the internal lens groups. Since the amount the focal length change varies from design to design, this may be a contributing factor the author’s assertion, I don’t really know.

The abridged version of the methodology goes something like this. With the 70-200 focused at infinity and zoomed 70mm, I moved the camera around keeping the wall and sensor parallel until I had the edges of the sensor lined up with something I could measure. I measured that distance, and the distance from the film plane to the wall then subtracted 5.35” from the camera/wall distance to get the distance from the lens’s optical center to the wall. In my case, I measured the distance on the wall at 44 inches, and the distance from the lens’s optical center to the wall at 87.15 inches. Plugging that in gives me an angular field of view of 29.34°, which is right about what you should expect for a 70mm lens on a 36mm wide sensor.

Working backwards though the field of view equation, , results in an focal length (f) of approximately 71mm. Close enough for me to be unconvinced about the author’s assertions or that Canon is misrepresenting focal lengths.

Second, I have worked in photo retail and own a lens rental company and I can honestly say that no one ever bought or rented an 24-105 f/4L IS over a 24-70 f/2.8L because of the additional 35mm of range.

Before I go any further on that, I want to point out something about the 35mm of additional range. While 35mm doesn’t sound like a lot, it can be quite significant. Go 35mm wider than 50mm and you’re not going to miss the differences. In fact, focusing on it being only 35mm belies that it is in fact a loss of 50% compared to the 24-105. In fact, the difference in going from 70 and 105mm is considerably more pronounced than the difference in going from 105 to 135mm.

While I can’t argue with the author’s experience, I can provide a data point to the contrary (god I love invalidating absolute statements). I bought an EF 24-105mm f/4L IS USM because of the increased range, decreased weight, and IS in that order. Price wasn’t really a consideration, doubly so since I already owned a 24-70/2.8L before I bought the 24-105.

The simple reality of it is that for me, the 24-105 fills a need that a 24-70 can’t, even if it’s stabilized. My 24-105 is my choice for cutting down weight, not just because it’s lighter than the 24-70, but because it covers 30% of the range of a 70-200, which often means I can leave that at home too. Which brings me to the following.

I also think that people will like not having overlap if they have a wonderful EF 70-200 f/4L IS, or 70-300 f/4-5.6L IS.

As far as I’m concerned, some overlap is not a bad thing at all.

Overlap is flexibility. It means not having to change lenses as often in situations where you’re dancing right on what would otherwise be the boundary between lenses.

Overlap is not having to carry as much gear all the time. If you’ve got a 17-40, 24-105 and 70-200, you can take just the 17-40 and 70-200, or just the 24-105 and leave the rest and not be completely without coverage. Give up the overlap, and you’re taking all 3 lenses, just in case.

We obviously all see the photographic world though our own lens. For me the 24-70 f/4 IS is something of a mixed bag. On it’s own, as an addition to Canon’s lineup, the EF 24-70mm f/4L IS USM looks quit solid. I don’t personally think the maximum magnification or hybrid IS as nearly the selling point the CR author or Bryan at The Digital Picture see it as, but the lens isn’t something to sneeze at either.

As a kit lens for the 6D, I’m somewhat left wondering if it’s a good of a deal. I guess that call really comes down to whether or not more reach is desirable or not. Personally, I find it unlikely that I’d ever recommend the 24-70/4L IS over the 24-105/4L IS. Putting aside the differences in image quality, having carried and used both ranges I find it simply impossible to go against the increased focal range. Moreover, while the maximum magnification sounds impressive at first blush, the working distance will be ruthlessly short.

However, if this is intended to be a replacement for Canon’s EF 24-105mm f/4L IS USM, then I think Canon will have missed the boat. I seriously hope that’s not the case.

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