A beginner to photography often wonders what using those mighty 'L' lenses is like. They often hear rich photographers swearing up and down that any lense not bearing the 'L' designation is useless. The term 'consumer grade lense' is said with a sneer and an upturned nose. Often the beginner is left feeling that the equipment he/she can afford will never produce quality photographs.I happen to be one of those photographers that can afford those expensive lenses. And yet I only use a single lense that bares the 'L' designation. My other lenses are all of the 'consumer grade' variety. I don't want the 'L' versions of the other lenses I own. They're too heavy. They're too white. And the lenses I'm using already do the job just as well.
But isn't 'L' glass always better than 'non-L' glass? The answer to that question is flatly no.
Let me qualify that. The L version of any particular lense always includes additional optical performance in areas the non-L version just can't reach. In most cases, that means it can take sharper photos at wider aperatures than the equivalent non-L version can.
But what if the photos you're shooting don't call for a wide aperature?
_That_ is why I'm saying 'L' glass isn't always better than 'non-L' glass. When wide aperatures aren't needed, the non-L version generally performs just as well as the L version. In some cases, they even perform better. And yet the the non-L version is usually less than half the weight and substantially less bulky. The lighter lense is easier to hand hold and easier to move around with. Especially over long periods.
In short... under such conditions the smaller 'consumer grade' lense is actually better.
Now, I'm not talking about the el cheapo lenses here. The cheapest bottom of the line zoom lenses are targetted at beginners who don't know any better, and they really are garbage. I'm talking about typical moderately priced lenses. All the average decent stuff.
As the aperature is closed down, more and more of the physical lense is literally not even being used. When you think about it this way, it becomes obvious why larger wide aperature lenses lose their advantages over smaller lenses as the aperature used in the photograph gets smaller. The extra glass isn't actually being used at all in that case.
Now if your photographic subject calls for lense capabilities which fall within the range that only an 'L' lense can do well, then obviously the 'L' lense is the better choice. I have one such lense in my set because I have found a common need for it in the photography that I do.
Anyway... to back up what I'm talking about, I'm going to provide some comparison photos.
Each comparison is a blow up of a small piece of the picture taken by both lenses. The camera used was a Canon EOS D30 set for mirror lockup and mounted on a Bogen tripod. The subject is the cover of a book shot from some distance away.
The left photo in each comparison was shot with a Canon EF 200mm f2.8L prime lense. The right photo is shot with the Canon EF 75-300mm f4.0-5.6 IS zoom telephoto lense. Note that not only is this a comparison between L and non-L, but also between prime and zoom. While the 200mm f2.8L is reputed to be intensely sharp, the 75-300mm IS lense is often ridiculed on the internet as a very soft lense with weak optics. Further, since the camera is firmly mounted on a tripod, the IS function of the 75-300mm is useless. Further still, the 75-300mm is weakest in its 200mm to 300mm range... especially at 300mm. All of these factors strongly favor the 200mm f2.8L prime lense. The seperation in quality between these two lenses for these tests should be about as wide as it gets within the Canon lineup.
These photos are virtually identical in quality. The 200mm prime is slightly better. But only on close side by side comparison.However, the 200mm prime wide open is nearly two stops faster than the 75-300mm zoom. So this isn't actually an even comparison between the two at all. It just shows that their quality is similar at 200mm in a wide open state.
All lenses are at their weakest when they are wide open. L glass is no exception.
There we go. This comparison clearly shows where the 200mm prime shines over the 75-300mm. At f5.6, the zoom lense is still almost wide open. But the 200mm prime is stopped down 2 whole stops from its wide open state. There's a very big difference between the two in terms of definition and sharpness.
Whoa! What happened?! Are these still the same two lenses?Indeed they are. But the results from both lenses are virtually identical. One is very slightly darker than the other, but that's an exposure difference due to an open window and changing sunlight outside. In terms of image definition, I don't think I could determine which lense took which photo in a blind test. In fact, my friend even pointed to the one on the right and told me that it was the sharpest one before I labelled them.
At f8.0 and higher, these two lenses are showing identical photographic quality.
This is a bit less of a straight test. The 200mm prime has been fitted with a Canon 1.4x extender to boost it to 280mm. The images have been scaled slightly to match eachother since the prime lense doesn't actually quite reach 300mm.But, nevertheless, it's very obvious that the 75-300mm is quite weak wide open at 300mm. Zoom lenses are usually weakest wide open at their longest settings. It's produced a usable image, but the results aren't stellar. Taking photographs under this condition is best avoided.
The prime lense and extension combo, on the other hand, is stopped down one whole stop. And its quality looks very good. It even picks up the dithering pattern in the printing on the cover quite well.
Closing the aperature just one stop produces a big difference in the quality of the 75-300mm side. Notice a pattern here? From wide open to closed down one stop is the greatest transition in image quality for any lense, L glass or not.It's still not as sharp as the other side though. But it's pretty close. It is picking up the dithering pattern in the printing also, though not as well. It wouldn't be very easy to tell the difference between the two lenses in a normal photograph at this aperature. Remember that these comparison images are blown up from only a small portion of the actual photograph.
And here we are again. The results are practically identical once the 75-300mm zoom is at least two stops down from wide open.
At wide aperatures, the 200mm f2.8L prime is very clearly better than the 75-300mm f4.0-5.6 IS zoom.But when the aperatures aren't so wide, the optical quality of both lenses are equivalent. And if these were real world targets taken under real world conditions, you can bet the IS function and zooming capabilities on the 75-300mm would help level the playing field. But that's not the point I was trying to make.
My point was that 'L' lenses are not magical. They don't inject magic into every photograph like their owners would often have you believe. They perform better at the edges of the photographic range. But that's all. Outside of that, they're just heavier and more bulky to do the same job.
Again, that's not to say that 'L' lenses are not useful. If your photographic needs call for those difficult ranges, then you really do need one.
But pay attention to what aperatures you're actually using in your photographs. If you're consistently pinned at or near wide open aperature, then a better lense would help. But if that's not the case, then a bigger, heavier, and more expensive lense would only be more to carry around. It wouldn't improve your photographs at all.
There's no point in being able to shoot well at wider aperatures than you actually use.