I have updated my Sharpness and Aperture Selection of Full-Frame DSLRs post to include the corner crops from the same photos used for the center crops that were already there. Here’s the image I added – see the link for full information.
Tag Archives: L
Sharpness and Aperture Selection on Full-Frame DSLRs
(Note: This article was originally posted in 2007 and I should probably update the test using newer gear – though the point of the test and the post remains.)
Last month I wrote about a set of tests (“Full Frame Lens Test“) that I conducted with my lenses and my Canon 5D body. My object was simply to better understand how the camera/lens combinations would behave so that I could make better decisions about appropriate lenses and apertures while making photographs.
One discovery was that, compared to using a crop sensor DSLR, I can get excellent results when I shoot at smaller apertures with good lenses on the full frame body. I tended to avoid apertures smaller than about f/8 on the crop sensor camera, but there seems to be little or no real liability in using f/11 or even f/16 on full frame.
To illustrate I put together the following composite image. (The image appears in reduced form on this page. Click the link to see the full size version.)
The example includes five versions of a small section from near the center of a photograph taken with the Canon EOS 5D using the EF 24-105mm L IS lens at a 50mm focal length. The camera was on a tripod, MLU and a remote release were used, and the AF was turned off. The images are 100% crops – in other words, actual pixel size is displayed in these tiny excepts from the much larger original images. (You would virtually never view a print at this magnification. These are equivalent to tiny sections from a print that might be about 5 feet wide!) The images have been slightly sharpened in post-processing, but are otherwise unaltered.
I shot at apertures of f/4, f/5.6, f/8, f/11, and f/16. In terms of the sharpness of this portion of the image, I am quite certain that all five examples are plenty sharp for making prints. That said, there are some differences. To my eye:
- The f/4 and, to some extent, the f/5.6 versions are slightly but noticeably softer at this magnification.
- The f/8 and f/11 versions seem to me to have approximately equal sharpness. Some parts of the f/8 image seem slightly sharper, but other parts of the f/11 image seem sharper. In the end they are pretty darn equivalent, though I’d maybe give the f/11 a very slight edge overall.
- The f/16 image may be slightly less sharp than the f/8 and f/11 versions, but the difference would not be noticeable in a print, even a rather large one. In any case, f/16 appears sharper than either f/4 or f/5.6.
After doing this test I no longer hesitate to shoot at f/11 or f/16. Not only does this give me the possibility of getting greater depth of field when I need it, but it also means that I can compensate for corner softness on some lenses (e.g. the 17-40mm) by using a smaller aperture without fear of losing center sharpness.
(Addition: 4/23/07 – Other Canon L lenses seem to give similar results, including my 17-40mm f/4 L and my 70-200mm f/4 L.)
Added 2/23/08:
In response to a question in a photo forum I put together a sample image showing corner sharpness from the same original images used in the example above. (The earlier example shows 100% crops from near the center of the frame.)
(image temporarily unavailable) 
Technical info: Shot using a Canon 5D with the Canon EF 24-105mm f/4 L IS lens at a 50mm focal length. In aperture priority mode, the aperture was changed manually between shots. Initial focus was with AF, which was then switched off before shooting the series. Camera was on a tripod and MLU and remote release were used. Shots were converted from RAW with ACR and no additional post-processing applied. Print made at this resolution would be approximately five feet wide. The crop is from the far lower left corner of the frame.
In addition to noting the softer image in the corner at f/4, also note that the image is a bit darker due to the expected increase in corner light fall-off (“vignetting”) at the largest aperture. Sharpest version in this series shot with a FF body seems to be at f/11 as in the center crop example above. But note that f/8, f/11, and f/16 are not very different in overall sharpness – and in the end any of these apertures would produce a very sharp print.
In response to another forum discussion, I have added another example, this time using the Canon EF 50mm f/1.4 lens and showing performance at f/5.6, f/8, f/11, and f/16. In other respects the test is the same as described already in this post. This image is seen to the right and below.
(image temporarily unavailable)
Conclusions: Based on this set of images and other taken with different lenses under similar conditions, I have come to some conclusions that work for me with my Canon lenses and full-frame Canon 5D body.
- In general the sharpest whole aperture seems to be around f/11.
- It is very difficult to distinguish any resolution differences at f/8 or f/16 – there are subtle differences when viewing the test images at 100% magnification on my monitor but these are essentially invisible in prints.
- f/5.6 or f/22 will tend to be a bit less sharp, though perhaps not for the same reasons. At f/5.6 I begin to notice a bit more of the diminished sharpness as a lens is opened up – more on some lenses than on others. At f/22 the effects of diffraction become just a bit more noticeable. However, if the shot demands it I do not hesitate (much) to use either of these apertures as the very slight decrease in sharpness is quite tiny if visible at all in a print and both provide some other advantages in certain situations. (I’ll even use the largest f/4 aperture on the test lens when isolating the subject is important or when low light demands it – and the results will typically be just fine.)
- At larger apertures the performance becomes more tied to the particular lens so it is more difficult to make any generalizations beyond the fact that vignetting increases and sharpness will be less optimal.
- The smaller apertures decrease any corner light fall-off (“vignetting”) or softness, generally to a point where both are insignificant.
- With all of this in mind, unless I have a reason to select some other aperture I typically use f/11 as my general starting point when shooting with my full-frame DSLR body.
G Dan Mitchell is a California photographer whose subjects include the Pacific coast, redwood forests, central California oak/grasslands, the Sierra Nevada, California deserts, urban landscapes, night photography, and more.
Blog | About | Flickr | Twitter | Facebook | Google+ | 500px.com | LinkedIn | Email
Text, photographs, and other media are © Copyright G Dan Mitchell (or others when indicated) and are not in the public domain and may not be used on websites, blogs, or in other media without advance permission from G Dan Mitchell.
Canon EF 24-105mm f/4 IS L Lens
I have owned the Canon EF 24-105mm f/4 IS L lens since 2006. I originally picked this lens for several reasons:
- On my full-frame cameras, this lens covers a very useful range from fairly wide to slightly long, making it a very flexible and versatile lens.
- The lens is quite sharp and has good contrast throughout its focal length range.
- For its focal length range the lens is relatively compact. This is important to me since I frequently hike or backpack with photo gear.
- The f/4 maximum aperture is generally sufficient for the kinds of photography I do.
- The image stabilization (IS) feature is helpful for handheld photography and somewhat compensates for the f/4 maximum aperture.
Like most lenses, this one has a “personality” that gives it particular strengths and weaknesses relative to the individual photographer’s work and working methods. My extensive experience with the lens convinces me of the following:
- Resolution is very good when the lens is used with care. Sharpness is excellent throughout the focal length range, being best in the middle portion as expected. Sharpness can diminish a bit at the long end compared to, say, 50mm – but this is usually not a reason to switch to another lens except in those cases where I have plenty of time to do so.
- Vignetting (corner light falloff) is certainly noticeable at f/4 and especially so at the shortest focal lengths. For most of my photography this is not an issue since I most often shoot at smaller apertures. However, I do shoot the lens at f/4 and wide angle focal lengths. In these cases a) the vignetting is actually a nice effect with some subjects, b) it can be corrected easily and pretty much automatically in post when necessary.
- Barrel/pincushion distortion is mostly not an issue, though the lens does produce noticeable barrel distortion at 24mm. Here the situation is somewhat similar to that with vignetting. In most cases, I don’t even notice the barrel distortion in actual photographs. I do notice it in photographs that have lines parallel to and close to the edges of the frame. When necessary, I let my raw conversion software (ACR) apply an automatic correction and the image lines up nicely and still has very good resolution.
- There is a false notion that this lens is not sharp at 24mm. This is incorrect. I think that this rumor -which is what it is – got started on internet discussion boards where people morphed the descriptions of the vignetting and barrel distortion into “poor performance at 24mm” and then further to “must not be sharp.” This is simply wrong. Sharpness is fine at 24mm.
- Handling is great. Compared to the lens sometimes cited as an alternative, the 24-70mm f/2.8 L, this lens is more compact and a bit lighter. The lens is solidly built and the controls are accessible and easy to use.
- Over time any lens can go out of adjustment and require service. If you use your lenses a lot, you will eventually discover this truth. In my experience, two particular issues might eventually come up with this lens. First, I notice and others have described the development of “zoom creep” after a time. The tension on the zoom mechanism seems to loosen and if you point the lens straight down it may “zoom out.” Second, although I have only my own experience to go on here, I have a slight suspicion that the lens may be a bit more susceptible to going out of adjustment with rough treatment compared to some other Canon zooms. After a few years of being banged around on the trail, mine had to go in for adjustment of a focus issue on one side of the image. After adjustment it came back working great.
- While a f/4 zoom is generally not going to be a super bokeh lens (though there are exceptions), this lens does OK. It can produce slightly “busy” bokeh at some middle apertures. Surprisingly, it produces very nice bokeh when used with an extension tube for macro work. (In fact, for hand held photography of things like wildflowers, extension tubes attached to this lens with its IS feature can work very well.)
The dimensions of the lens are similar to, but slightly larger than, my 17-40mm lens. However, the 24-105 is noticably heavier, though not enough so to compromise its use as a walk-around lens. Speaking of which, it is regarded by many as a nearly perfect lens for this role on full-frame bodies. In fact, I’ve had great success using it for street photography!
On a 1.6 crop factor body it is less useful as a single lens solution than it is on a full frame body, since 24mm is not all that wide on this camera. (It is roughly equivalent to a 38mm lens of a full frame body which is only moderately wide.) I did use it on a cropped sensor body for about a year when I first purchased it. In practice, I found that I tended to switch back and forth between the 24-105 a wider zoom a lot. Unless you are not fond of wide angle shooting or you like to switch lenses a lot, there can be better solutions for use on cropped sensor bodies. The following are a couple of other lenses to consider if you shoot a cropped sensor body: Canon EF-S 15-85mm f/3.5-5.6 IS USM Lens or
Canon EF-S 17-55mm f/2.8 IS USM Zoom Lens. (The links go to site sponsor B&H Photo.)
My article on backpacking photography discusses how I combine the 24-105 with other lenses to produce a very viable and reasonably light backpacking kit. In a few cases I have gotten along quite nicely on pack trips with just the 24-105 , though in most cases I combine it with the Canon 17-40mm f/4 L and/or the Canon EF 70-200mm f/4 L for more flexibility.
Bottom line: I’m quite happy with the EF 24-105 f/4 IS L lens. Color and contrast are great and it is very sharp for a zoom. The zoom range is excellent on a full frame body and might be useful for some shooters even on a 1.6 crop factor camera.
Related:
- Tests and Reports page.
This lens is available from site sponsor B&H Photo, and your purchase though links at this site help support the blog. If this information was useful to you in making your decision, please consider purchase through the following link: Canon 24-105mm f/4L IS at B&H
Other gear mentioned in this article, with links to B&H:
- Canon EF-S 15-85mm f/3.5-5.6 IS USM Lens
- Canon EF-S 17-55mm f/2.8 IS USM Zoom Lens
- Canon EF 70-200mm f/4L IS USM Lens
G Dan Mitchell Photography
About | Flickr | Twitter | Facebook | Google+ | 500px.com | LinkedIn | Email
Text, photographs, and other media are © Copyright G Dan Mitchell (or others when indicated) and are not in the public domain and may not be used on websites, blogs, or in other media without advance permission from G Dan Mitchell.
(Basic EXIF data is available by “mousing over” large images in blog posts. Leave a comment if you want to know more.)
Canon EF 17-40mm f/4 L Lens
Updated on July 6, 2014 – After relying on this lens for nearly 10 years, I am about to replace it with a Canon EF 16-35mm f/4 L IS, a lens that just recently became available. (I’ll review that lens a this blog after I have a chance to use it.) With this change in mind, I am updating this post one more time.
The Canon EF 17-40mm f/4 L lens has long been a core lens in my kit, covering the wide to ultra wide angle range on my full frame cameras. For my primary uses it is a great performer. It is almost always in my kit when I backpack, and I often use it for landscape photography and occasionally for other types of photography, too.
As I have written elsewhere, every lens has a “personality” that makes it more or less suited to different types of photography and different photographers. This personality is the result of the relative strengths and weaknesses of the lens. No lens is objectively “best” in all ways, so the real interesting question is how well various lenses line up with your specific needs. With that in mind, here are some observations about the 17-40 based on nearly a decade of use since 2005.
- Overall, the lens is capable of excellent resolution. Center sharpness is good at all apertures (leaving aside for the moment the effects of diffraction blur that will soften the image from any lens at very small apertures) and it can be quite good when the lens is stopped down a bit. It is important to note that ultra wide zoom lenses (and even prime lenses) can have some issues with sharpness and other factors such as chromatic aberration, especially in the corners of the frame. This lens is not immune to these issues of ultra wide lenses, though it handles most of them quite well in many cases.
- Corner sharpness varies depending upon aperture. In my experience, the lens shows noticeable corner softness at f/4. Whether or not this is a problem depends a lot on how you will shoot the lens and what your expectations are. I have used the lens wide open for street photography in closed-in spaces, and the soft corners added a character to the shots that I liked. If you require something closer to corner-to-corner sharpness wide open, the Canon EF 16-35mm f/2.8L II is likely to be a better choice if you mainly shoot low-light, hand-held, full-frame work. (Read more about the 16-35mm options later in this post.) However, if you are looking for an ultra wide zoom to shoot more static subjects from the tripod and you will use smaller apertures for larger depth of field, the 17-40 is just as good – and lighter and less expensive to boot. Stopped down a bit and on the tripod, the 17-40 produces excellent results.
- In mid-2014 Canon introduced another alternative lens, the EF 16-35mm f/4 L IS. This lens offers significantly better corner performance that either of the earlier lenses along with image stabilization. This lens offers significant improvements to corner performance, a narrower focal length range, and a price that is roughly between that of the 17-40 and the f/2.8 16-35. (Read more about this option later in this post.)
- The lens has a great reputation for resistance to flare, and my experience is in line with this. This may be more important in an ultra wide lens since its wide field of view is more likely to include the sun or other flare-producing light sources, and because the shallow lens hoods that are required for ultra-wide lenses don’t really shade the lens much at all.
- Build quality is just what you would expect in an L lens, and there is something about the compact and simple nature of this lens that seems to give it an even more solid “feel,” for whatever that might be worth. Along these lines, it uses 77mm filters, which are very common on other L zooms.
If you poke around on the net long enough, you’ll find posts that suggest that the 17-40 isn’t sharp enough or that the 16-35 is a better choice. This turns out to lead to some complicated issues, so let me take a shot at dealing with them
- Is the 16-35 sharper than the 17-40? Yes and no. The 17-40 is just as sharp (or even a bit sharper) in the center at any aperture, though it is not as sharp in the corners at the largest apertures. So, “yes” if you mainly shoot wide open in very low light. But “no” if you mainly use the ultra wide lens stopped down while shooting from the tripod, for things like landscape and architecture.
- Is the 17-40 poor in the corners? Again, yes and no. First, many ultra wide angle lenses have issues in the corners – this is pretty much the nature of the beast. (There are a few exceptions, but they tend to be very specialized and very costly. Note: I’m expecting that the new Canon 16-35mm f/4 L IS may be one of this exceptions.) Second, wide open the 17-40 is not great in the corners, at least in my experience. At f/4, and to a lesser extent f/5.6, the corners are soft and for several reasons. However, stopped down it is much better in the corners — as good as its traditional Canon alternative, the 16-35mm f/2.8. (Some of the reports of poor corners seem to come from a typical characteristic of many ultra wide “test shots,” which often include very close scene elements in the lower corners – and the issue is more about DOF than about lens sharpness.
- If you shoot a cropped sensor camera, neither of these will likely be the best choice – more on that below.
On full frame, this lens complements any of the 24mm-xxmm L zooms. It does overlap their focal length ranges a bit, but I find that useful for several reasons. (I shoot the EF 24-105mm f/4L IS and the EF 24-70mm f/2.8 L II. (See more about these lenses here: “Canon 24-70mm f/2.8 L II vs. 24-70mm f/4L IS vs. 24-105mm f/4 L IS“) First, it means that I am a bit less likely to need to change lenses. Second, it means that I can sometimes stay away from the ends of the focal length ranges of either lens, and this can produce just a bit more image quality in some cases.
Some photographers combine the 17-40 with a Canon EF 70-200mm f/4L IS USM lens (link to B&H) and then add a 50mm prime to “fill the gap.” I don’t do this, but I can understand how it could work well and save some weight and bulk.
The 17-40 f/4 L on Cropped Sensor Bodies
Some photographers like to use this lens on their cropped sensor cameras. I used mine on a cropped sensor body for the first year or so that I owned it, but I’ve used in exclusively on full frame bodies since that time. In my view it is merely OK on cropped sensor cameras, but not a stand out performer. The main issue is that, in my experience, you end up caught between the proverbial “rock and a hard place.” The “rock” is the relatively conservative f/4 maximum aperture with its less than stupendous corner performance. The “hard place” is the issue with diffraction blur occurring sooner as you stop down on cropped sensor cameras – many feel that you would want to be cautious about stopping down much past f/8 for this reason on crop. This doesn’t leave you with a lot to work with: f/4 is a bit soft in the corners. f/5.6 is getting better but isn’t yet great. f/8 is pretty good all around. At f/11 diffraction blur starts to become a concern. In the end, you really have only one truly good aperture. Fortunately, cropped sensor camera shooters have a great alternative in the Canon EF-S 17-55mm f/2.8 IS USM Zoom Lens. It provides better large aperture performance, a wider range of apertures at f2.8, image stabilization, and a larger focal length range. For this reason, I tend to recommend it over the 17-40 for cropped sensor shooters.
Cropped sensor shooters contemplating an ultra-wide angle lens should be aware that this focal length range does not provide equally wide angle-of-view coverage on their cameras. On these cameras the 17-40mm and 16-35mm focal lengths range from merely wide to a bit longer than normal. Basically, if you shoot a cropped sensor camera and you want ultra-wide… you do not want any of these lenses! Canon does make a lens that provides ultra-wide coverage on your cropped sensor camera though. It is the EFS 10-22mm f/3.5-4.5 lens. This is a fine lens for things like landscape photography, and the angle-of-view coverage on cropped sensor cameras is equal to that of the 16-35mm lenses on full frame.
(Note that these EFS lenses are not designed to work on full frame cameras.)
Compared to the Canon EF 16-35mm f/2.8 L II
The Canon alternative to the EF 17-40mm f/4 L has long been the Canon EF 16-35mm f/2.8L II. (The current, newer version is signified by the addition of “II” to its name.). A few important points include:
- This 16-35mm lens provides one additional stop at f/2.8, which is useful to those doing handheld ultra-wide angle photography. It is a popular and useful lens for things such as journalism, wedding, and event photography for this reason.
- This lens also provide better corner performance at large apertures where the 17-40 shows its corner weaknesses, especially at f/4 and to lesser extent f/5.6 and possibly f/8.
- The 16-35mm f/2.8 II is no better than the 17-40 at smaller apertures, where the 17-40 is at least as good and perhaps marginally better in some ways, so there is little advantage in the 16-35mm f/2.8 for landscape photographers and those doing similar work who may typically shoot such a lens at smaller apertures.
- The 16-35mm f/2.8 II is approximately twice as costly as the 17-40mm lens. It is also larger and heavier.
- The II version of the 16-35mm lens uses a larger 82mm diameter filter thread. (The older version has a 77mm thread diameter, which is common to a number of Canon L lenses.)
Compared to the Canon EF 16-35 f/4 L IS
As of the date of the current revision of this post, Canon had just introduced a new EF 16-35mm f/4 L IS lens that can be an alternative to the 17-40mm f/4 L and, for that matter, to the older EF 16-35mm f/2.8 L II. Some considerations follow:
- Although this lens has the same f/4 maximum aperture as the 17-40mm lens, it adds image-stabilization (IS). IS allows you to hand hold the camera at lower shutter speeds by compensation for camera motion/vibration.
- Every review I have read reports much better corner performance than that of either the 17-40mm f/4 or the 16-35mm f/2.8, including very good performance wide open. The best performance seems to be at the shortest focal lengths, where the coverage does not overlap that of longer zoom lenses. (I will update this section based on my own experiences after I have a chance to use the lens.)
- This lens is larger and heavier than the 17-40mm lens, being more like the 16-35mm f/2.8 in these characteristics. It is priced midway between the other two lenses.
- This lens uses the more “standard” 77mm filter threads.
The Bottom Line
In some ways, this is almost as much a post about options for covering this focal length range as it is about the 17-40 f/4 L itself. It is also a good example of the fact that there is no one “best lens” in a general sense, but that it is really about which lens is right for your particular needs. With that in mind, a quick recap of three options along with some general ideas about situations in which any of them might be a best choice:
- If you use a full frame camera, mostly shoot from the tripod, and tend to favor smaller apertures for greater depth of field and other reasons, then the 17-40mm f/4 L could be the best choice for you. It is smaller and lighter than the alternatives and costs quite a bit less.
- If you want the best overall lens performance performance and can get along with image stabilization and without the f/2.8 aperture, the new EF 16-35mm f/4L IS may be your best option.
- If you use a full frame camera and often shoot handheld in low-light situations and thus need to use larger apertures, the 16-35mm f/2.8 L II could well be the best bet for you. Of course, it can also do much of what the 17-40 will do, though with a higher cost, smaller focal length range, and greater weight and bulk.
- If you shoot a cropped sensor camera the EFS 17-55mm f/2.8 IS is probably a better choice than either of the L lenses for you – with its excellent optical quality, f/2.8 aperture, image stabilization, and larger focal length range.
Bottom line: The EF 17-40 f/4 L is a great lens for full-frame photographers who want a versatile ultra-wide angle lens for shooting large DOF subjects from the tripod, including subjects such as landscape and architecture. Its lower cost, smaller size, and lighter weight are bonuses – the latter two especially so for those who work while traveling on foot.
This lens is available from site sponsor B&H Photo, and your purchase though links at this site help support the blog. If this information was useful to you in making your decision, please consider purchasing through the following link: Canon EF 17-40mm f/4 L at B&H
If the information in this post has helped you arrive at a purchase decision, please consider using these links to make your purchase from site-affiliate B&H Photo. Your price will be the same, you’ll purchase from a reliable vendor, and a small percentage of your purchase price will help support this website. Thanks!
In addition to the Canon EF 17-40mm f/4 L, other lenses mentioned in this article and available from B&H include:
- Canon EF 16-35mm f/4 L IS USM Zoom Lens
- Canon EF 16-35mm f/2.8L II Zoom Lens
- Canon 24-105mm f/4L IS at B&H
- Canon EF 70-200mm f/4L IS USM Lens
- Canon EF-S 17-55mm f/2.8 IS USM Zoom Lens (for Canon cropped sensor cameras only)
- EFS 10-22mm f/3.5-4.5 Zoom Lens (for Canon cropped sensor cameras only)
Related posts:
- Canon 17-40mm f/4 L Sharpness: Two Examples
- Corner Sharpness of the Canon 17-40m f/4 Lens on Full Frame
- Canon EF 17-40mm f/4 L: Testing a Claim About Sharpness and Focal Length
- Canon EF 17-40mm f/4 L at B&H
G Dan Mitchell Photography
About | Flickr | Twitter | Facebook | Google+ | 500px.com | LinkedIn | Email
Text, photographs, and other media are © Copyright G Dan Mitchell (or others when indicated) and are not in the public domain and may not be used on websites, blogs, or in other media without advance permission from G Dan Mitchell.