Notes on the Canon 24-105 F4 IS Lens

The other day I thought it would be fun to bring out my Canon 24-105mm F4 IS L lens and put it up against my CN-E 24, 50, & 85 cinema primes on the C300. I love my 24-105, and use it quite often. I'm often tempted by it's convenience factor, but this test really opened my eyes, & the results were quite telling. I shot everything at F4 on the zoom, and T4 on the primes. I don't have time just now to post up the results, but here are my findings:

At 24mm, my 24-105 is quite sharp and resolves very, very close to what the 24mm prime gets. I think the increased micro-contrast of the prime gives it more perceived sharpness, but the actual resolved detail between the two is nearly the same (remember, we're talking HD resolution here). The 24mm prime has a noticeable 'zing' compared to the zoom. Color is more vivid with the prime and better contrast.

At 50mm, we see the resolved detail of the zoom lens start to wane just a bit. Micro-contrast is playing a big role here, but in the finest details, you can see a definite difference. Again, the 'zing' factor is there. Color and contrast is in a different league.

At 85mm, there's a different story. The prime is considerably 'crisper' and whereas you might be able to add post sharpness to make them close, there's no denying that the prime is flat-out eating the zoom lens for lunch. Color and contrast between the two lenses aren't even existing in the same dimension at this point.

In all three focal length samples, the prime lenses give a far snappier image, with much more vivid color and very crisp details. The 24-105 looks a quite dull next to the cinema primes, but for the price, it really should, I suppose!  The more you look at comparing images, the duller the 24-105 starts to seem.

Transmittance - now here's where things get really weird. The transmission of the zoom is just a hair more than 2/3 of a stop darker than it's advertised aperture through these three focal lengths when aperture is wide open at F4. Oddly enough, at F4, there is ZERO transmission loss through the entire zoom range. If you stop down, though - even to just F4.5 - you'll begin to lose almost half a stop from widest to telephoto. By the time you stop down to F5.6, you'll be losing almost a whole stop by zooming from 24mm to 105mm! It's the weirdest thing, and I can't figure out what's going on to make that happen. By all means, go test this for yourself with a white card - set your in-cam waveform for spot and watch what happens to that area. I nearly fell off my chair when I saw it happening.

Anyway, there's always a price to pay for convenience - and I must say that the 24-105 has that in spades. If you're in a situation where you need to be as versatile as possible and have no time for lens changes, this is a very strong choice and I'll continue to use mine for a long time to come. However, if you want the best image quality, and to save yourself some time in post, you can't beat prime lenses - and especially the Canon Cinema primes! The difference in quality is really palpable, and placing these lenses up against each other really made me see that three dimensional quality that great primes bring to the table. Images from the primes have a pop that is not easy to replicate with anything less than the absolute best zoom lenses, in camera or in post. Trying to get a 24-105 to look as good as prime in color grading would be like chasing the dragon, and I think it would ultimately never be possible to catch it.

Some of my notes for those that use and enjoy the 24-105: it's strongest at the wide end, losing detail and lustre toward the long end (this could possibly be beneficial for close-up shots in docs where there is often less than flattering lighting and no make-up on the subject.) If you want to avoid losing transmittance when you zoom, stay at F4 and ride the ISO for your exposure. As soon as you stop down, you'll get varying exposures as you zoom. Color and contrast is the biggest sacrifice in using this lens, but it's a beast of a doc lens for it's range and IS. It's a poor choice for narrative shoots, pre-set interviews, and any shoot where you have the luxury of changing lenses when necessary.

I'll try to post up some of my test images when I get the chance. Happy Holidays, everyone!