Let's have a look at the Canon 300mm f/4L IS, a moderately long, moderately fast telephoto lens for the Canon EOS system. It was released in 1997 and remains on sale today, over twenty years later, but like the 100mm f/2 I wrote about a while ago it has spent most of its life in the shadow of other, more popular lenses. Nonetheless it fills a niche, and I decided to try it out because 300mm is apparently just right if you're planespotting at Hong Kong airport.
Here's what the lens looks like:
The tripod foot is just slightly too small to use as a comfortable handhold, but you could always add a large quick release plate.
And here's Brad Pitt:
About a month after writing the rest of this post I took the lens off to Venice, where by coincidence there was a film festival.
It's interesting to see the diversity of equipment used by the press pack - SLRs, mirrorless cameras, Sony, Canon, Nikon, third-party lenses, even a mobile phone.
I have no idea who they are.
300mm is a classic focal length, good for a wide range of sporty-wildlify-portraity applications, often paired with a teleconverter. It's just at the cusp of the super-telephoto range, and I like to think that the advent of crop-sensor digital SLRs at the turn of the millennium breathed new life into 300mm, because suddenly it was 450mm. It's still very much a jack-of-all-trades, master-of-none, but a combination of cropping and standing further away can work wonders.
Canon sells the lens with a box and a case, but not a hood, because the hood is built-in. Built-in lens hoods were a Canon thing in the 1990s. The 300mm f/4's hood pulls out and twist-locks into place:
I wish more lenses had built-in lens hoods. Some lens hoods have an aggressive look, but the 300mm's hood is just a tube, and perhaps because of this the lens doesn't feel as conspicuous as other L-class lenses. As with Canon's other L-class primes the 300mm doesn't extend or rotate when it focuses. It has a 77mm filter thread.
With the hood retracted the 300mm f/4 is relatively compact. It's slightly heavier than an f/2.8 standard zoom, but it feels lighter because the body is less dense. It doesn't have weather sealing, but even after standing downwind of a bunch of dusty tanks at Tankfest I didn't notice any more dust inside the lens. I have no idea how it would stand up to rain. When you clean the lens afterwards I suggest you blow off the dust, then extend and lock the hood, then blow off the dust, then unlock the hood and blow off the dust again. Dust seems to collect in the hood mechanism.
Bit of history. The EOS system was launched in 1987. In the first year there was a limited selection of lenses, mostly cheap zooms, but at the top of the tree was the Canon 300mm f/2.8L USM, a big, heavy professional lens that showcased Canon's new ultrasonic focusing technology.
In the 1990s Canon fleshed out the EOS system, but for a while the range of lenses was very binary, split between halo designs such as the 200mm f/1.8L and 50mm f/1.0L at the top end and cheap plastic-bodied zooms and primes at the low end, with very little in the middle.
In particular there were no mid-range primes, so in 1991 Canon launched the 300mm f/4L, which was aimed at people who wanted 300mm but didn't want or couldn't afford the f/2.8. The 300mm f/4 looked very similar to the 300mm f/4 IS featured in this post - it was a metal-bodied, white-painted lens with a built-in lens hood and a 77mm filter thread - but unlike the IS version the minimum focus distance was three metres instead of one and a half metres. The IS' focus window labels the close focus distance as a macro range, although the maximum enlargement ratio is a relatively ordinary 1:4.
I'm going to stop highlighting the letter L. It's really awkward and I don't want to do it any more.
The non-IS 300mm f/4 existed long before the modern internet came into being and there's very little about it online. The few reviews I can find suggest that it's slightly sharper at f/4 than the f/4L IS but much the same stopped down. It's an interesting choice on the used market, but against it the youngest examples are now over twenty years old and Canon doesn't service it any more. The three metre minimum focus distance strikes me as awkward.
Optically the 300mm f/4 IS' only real deficit is purple fringing in some situations at f/4.
The controls are simple. Stabilisation mode two is single-axis only. The focus limiter prevents the lens from hunting below 3m. The tripod foot is removable although underneath it there are exposed screws.
The original 300mm f/4L was replaced in 1997 by the 300mm f/4L IS, which added generation one image stabilisation. I have one! You're reading about it right now. The IS unit is rated for two stops of stabilisation, and on a personal level I can get generally sharp images at 1/100th and decent usable images at 1/40th if I hold myself really still. Image stabilisation goes wrong if you activate it while the lens is on a tripod - I tried it to see what happened, and the viewfinder image jumped to one side and wobbled a bit. My hunch is that this does nothing for corner sharpness.
Bokeh is just fine. This image illustrations one of the problems with the 5D MkII, a camera which is now, frighteningly, just over ten years old - it doesn't cope well with highlights.
I have no way of formally testing the 300mm f/4L IS, and even if I did I wouldn't, because I don't have the expertise to do so. The reviews I can find are generally eight-out-of-ten, e.g. it's of a high standard but not exceptionally sharp, and over the last few years it has faced very stiff competition from a new generation of zoom lenses.
St Mark's Square shot at f/4, 1/180th, ISO 100, with IS.
Straight from the camera central sharpness is okay, but not bitingly sharp.
However a bit of sharpening can help that. There's a subtle red glow around highlight edges.
Similarly the extreme top-right corner is good but not great...
...but again it can be improved with a bit of sharpening and mild CA correction. My impression is that at f/5.6 the lens becomes fractionally sharper, but I couldn't see a convincing improvement.
Just for fun here's the same location shot at 200mm with a Canon 70-200mm f/2.8 IS.
For my purposes I have no issue with central sharpness wide open. Lensrentals' MTF testing suggests that the 300mm f/4 IS isn't on a par with the best 300mm f/2.8 or even 100-400mm zoom lenses in the centre of the image, but that it's more consistent across the frame, with solid corners and less distortion than a zoom lens.
Almost all of the images in this post were moving objects shot through a mass of air at relatively slow shutter speeds with a hand-held lens using image stabilisation. I suspect that although a 300mm f/2.8 might be theoretically sharper I would need a monopod (and permanent burst mode) to notice any significant improvement in image quality.
There's essentially no geometric distortion. There's a little bit of vignetting at f/4, but I didn't bother to correct it and you probably can't see it in any of these images. The sharpness is good enough that you can do quite aggressive cropping. Contemplate the following image of an IFV commander:
It's actually a close crop from this image, with the contrast boosted:
For the sake of comparison, the following image shows how 300mm stacks up against other focal lengths:
The red box is 400mm, the yellow box is 600mm. Cropped down to 600mm a 21mp image is roughly five megapixels, which is more than enough for the internet.
One thing. Most people on the internet love their 300mm f/4 IS, but there are some outliers. Some people seem to hate it, and I have no reason to doubt their sincerity. I have a theory; it's not great at close focusing distances, and if you shoot tame birds (for example) at the closest extreme you might be disappointed with the images. Here's a shot of a tree at fifteen metres or so, followed by a 100% crop of the extreme top-right corner, taken at f/8:
It's not razor-sharp and the last fifty pixels or so have some CA, but it's pretty sharp. Here's another target, also at f/8, but shot at the closest focusing distance:
As you can see the corner at close range isn't very good. Whether it's field curvature or just an ordinary lack of sharpness I know not. At f/8 central sharpness is fine at close distance (I can see the texture of the paper) but at f/4 it's not as good either, so perhaps the people who disliked the 300mm f/4 IS shot mostly at close range. Who knows. This section of the review strikes me as one of those things that I will take down and try to forget about in the future because a massive flaw in my methodology will become apparent, but I tried hard to make sure that the album jacket was perpendular to the camera, and the other corners were just as bad, although frustratingly they don't have detail in them.
Incidentally the Canon 5D MkII's autofocus system is mediocre, but the 300mm f/4 is fast and accurate and worked well enough at Goodwood.
f/4 isn't quite as background-melting as f/2.8, but it's not bad if the target is relatively close. It's a stop more background-melting than most zoom lenses, two stops if you don't like shooting your zoom lens wide open at 300mm.
I mention up the page that the 300mm f/4L IS tends to be overshadowed. That's because Canon makes a wide range of telephoto lenses, both primes and zooms.
The most obvious alternative is a second-hand Canon 100-400mm f/4.5-5.6L IS Mk1, by all accounts a very good lens. It's a push-pull zoom that tends to suck up dust, and the typical second-hand example is now over a decade old, but it has a powerfully appealing combination of range and general competence. I might have bought one, but it's heavier than the 300mm f/4 and I already have a very good 70-200mm zoom lens, so I would probably only ever use it at 400mm.
Furthermore the Mk2 version of the lens is a major upgrade, and I suspect that the Mk1 version of the lens still has some depreciation left. I can remember when they sold for £800; they're now roughly £600. The Mk2 version will eventually hit the used market, at which point the Mk1 will depreciate even more.
For these and other reasons I decided against the 100-400mm. The next obvious choice is the 400mm f/5.6L, a venerable super-telephoto from 1991 that's still on sale today. It occasionally pops up on the used market. On a technical level it's a bit like the original non-IS 300mm f/4. There's no weather sealing or image stabilisation and the minimum focus distance is 3.5m. Optically it's apparently good but not great. I've always assumed that Canon doesn't sell many of them, and that most people go for the 100-400mm instead. I wonder if Canon assembles new copies of the lens from a bin of parts that were made twenty years ago. Who knows.
I opted against the 400mm f/5.6L partially because of the minimum focus distance, partially because good examples don't come up very often on the used market, mainly because 400mm is less versatile than 300mm. Furthermore handholding a lens at 400mm without image stabilisation is difficult. Will Canon replace it, or drop it from their line-up, or keep it? I don't know.
The aforementioned purple fringing is generally a non-issue, but it can occasionally be problematic. Photoshop can fix it. This is also another example of the lens being not great at closer focus distances.
Anything else? The modern 70-300mm f/4-5.6 IS II - a black, consumer-level lens - is apparently very good, but I wanted something more robust. The ancient 100-300mm f/5.6L is apparently decent at 300mm, but it's made of plastic and used examples are very old. I would be nervous about its little plastic gears. I could buy a teleconverter for my 70-200mm f/2.8 IS, but I'm not keen on teleconverters. I would end up with a long, unbalanced lens that focuses slowly and doesn't perform very well wide open.
The 70-300mm f/4-5.6L IS (the white, odd-shaped L lens, not the consumer model) is apparently very good, but it feels redundant. Why not buy a 100-400mm instead? Canon has been selling 300mm f/2.8 and 400mm f/2.8 lenses since the dawn of the EOS system, but even the earliest examples are still very expensive on the used market. They're excellent lenses but I can't justify the expense.
At the highest end of the range Canon's 600mm and 800mm lenses are rare and exotic. They're not so much standalone lenses as the central element of an image production system. They require an infrastructure of monopods, assistants, a van, padded lens boxes, a relationship with a Canon specialist etc.
My impression is that when faced with the need for a telephoto Canon lens most people opt for the 100-400mm f/4.5-5.6L, for good reason - it's versatile, and I could probably have taken any of these photographs with one, albeit that I would have been shooting a stop down and the background would be more distracting. Nonetheless the 300mm f/4 IS more than justifies its existence. At the very least it gives me an excuse to get out of bed on a weekend.
