Posts Tagged ‘sharpness’
Ever since Canon’s new 24-70mm f/2.8L II arrived late last year, lens reviewers around the web have been saying very nice things about its sharpness. DxOMark is the latest tester to do so. Here’s what it has to say:
[...] the Canon EF 24-70mm f/2.8 MkII is the highest scoring professional fixed-aperture mid-range kit zoom of any brand in the DxO Mark database and comfortably outperforms rivals as well as the firm’s earlier Mark I version, particularly with regard to the sharpness levels across the frame. We’re used to seeing a noticeable deterioration in performance in the outer fields at longer focal lengths even with high-quality optics from the big-name marques but the new Canon bucks that trend.
The company writes that the main issue is the lens’ price of $2,500 — quite steep when compared to rival lenses. Check out the full review for a more detailed breakdown of how the new 24-70mm performs.
Modulation Transfer Function (MTF) charts are a very commonly used tool in the photo industry for measuring and describing how sharp a particular lens is. However, it’s a system that is largely enigmatic to those outside the realm of optic experts and camera gearheads.
For those of you who don’t want to learn how to read MTF charts, camera gear testing service DxOMark has announced a new metric that boils a lens’ sharpness down to a single easy-to-understand-and-compare number: the Perceptual Megapixel.
Despite its girth, weight, and price, Canon’s original 24-70mm f/2.8L is a highly-regarded general-purposes lens. When the followup Mark II version was announced back in February, the higher-price tag, similar specs, and lack of IS had many photographers scratching their heads. Then the reviews started coming out.
After being announced back in 2002 as a replacement to the 28-70mm, Canon’s 24-70mm f/2.8 (above right) quickly became an extremely popular and highly regarded lens due to its friendly all-around focal range and sharpness. When the Mark II version was unveiled back in February to succeed “The Brick”, as the Mark I version is called, photographers grumbled at its hefty $2,300 price tag, the fact that it uses an 82mm filter instead of 77mm, and the lack of Image Stabilization. Roger Cicala over at LensRentals tested out the new lens, and has extremely positive things to say about it:
This is short, sweet, and simple. The resolution absolutely, positively kicks butt and takes names. It is way better than the lens it replaces. It’s better at 70mm than the best Canon zoom I know of, the 70-200 f/2.8 IS II. It’s even better at 24mm than the sharpest 24mm prime we have, the Canon 24 TS-E. In the center, in the corners, it doesn’t care. We only had 5 copies to test, but they were all very similar with little copy-to-copy variation.
Resolution is not everything, of course. But it’s certainly an important thing. Unless the real lens reviewers find some dramatic problems with this lens, I’d have to lean towards worth-the-money on this one. I can’t believe I’m saying that a $2,300 standard zoom is worth the money. But then again, I can’t believe I’m seeing a zoom lens out resolve a $2,000 world-class prime, either.
Okay, okay. Time to sell a kidney.
Canon 24-70 f/2.8 II Resolution Tests [LensRentals]
Really more useful for landscape and macro photographers who are going to be shooting through very small apertures (f/22 and above), this video from FStoppers explains what diffraction is and how it can affect your shots. The trade off, as they explain in the video, is between a large depth of field and a sharp image; and the trick is to find your “sweet-spot.”
The difference isn’t as obvious on the video even at 1080p, so if you want to see full resolution examples be sure to head over to the original post.
You probably know that stopping down (i.e. increasing your f-stop number) can increase the sharpness of your subject, but how much should you stop down to boost resolution without losing that nice, creamy bokeh? Roger Cicala did some research on this question and writes:
For those lenses that do benefit, stopping down just to f/2.0 provides the majority of resolution improvement. The difference between wide open and f/2.0 is generally much greater than the difference between f/2.0 and the maximum resolution.
Getting the edges and corners sharp requires stopping down to at least f/4 for most wide-aperture primes, and some really need f/5.6. Stopping down to f/2.8 may maximize center sharpness but often makes only a slight difference in the corners, at least on a full-frame camera.
None of the lenses performed any better after f/5.6 (for the center) or f/8 for the corners. Most were clearly getting softer at f/11.
If you’re using a wide-aperture lens, stopping down to just f/2.0 will reap big gains in sharpness while still keeping the depth-of-field narrow. Furthermore, for some lenses you don’t really even need to worry about stopping down for sharpness, since it hasn’t a relatively negligible effect on the outcome.
Stop It Down. Just A Bit. [LensRentals]
As you might know, different copies of the same lens can vary in quality, and some people go as far as to purchase multiple copies to pick the sharpest one before returning the others. Roger Cicala over at LensRentals wanted to quantify exactly how much variation actually exists between copies of the same lens, so he subjected some to Imatest quality tests:
[...] while the Canon 100mm f/2.8 IS L lens is a bit sharper than the other two on average, not every copy is. If someone was doing a careful comparative review there’s a fair chance they could get a copy that wasn’t any sharper than the other two lenses. I think this explains why two careful reviewers may have slightly different opinions on a given lens.
That’s interesting to think about. Two highly objective reviews of the same lens could come to different conclusions about relative sharpness compared to other lenses, simply because there are differences among copies of that lens. Too bad reviews are usually based on a single copy of a lens, rather than the average performance of multiple copies.
Notes on Lens and Camera Variation [LensRentals]
One of the things you’ve likely seen when looking at product or review pages for lenses is an MTF chart, used by manufacturers to give consumers an idea of how sharp a particular lens is. If you’ve never gotten around to learning how to interpret these charts, here’s a helpful 10-minute video tutorial on the subject. Luminous Landscape and Cambridge in Colour have great tutorials on this as well if you’re more comfortable with text-based tutorials.
DOF Calculator is an app for Android phones that helps you easily calculate depth of field and hyperfocal distances. Simply tell it your camera, lens, and aperture setting, and it’ll spit out the numbers you need for optimally sharp landscape photographs. You can download it for free by searching for “DOF Calculator” in the Android Market.
For a quick video tutorial on how hyperfocal distance works, check out this post.