Rich1971 wrote in post #12863430
George, do the filters affect it that much?
Yes and no. Any time you add a layer of glass to the optics there is going to be some degradation of the image... With a simple, single layer filter such as a UV, you are adding two glass/air boundaries that the light rays need to cross, sort of complicating their path to the sensor. (Note: it's worse with multi-layer filters such as polarizeres and variable neutral density, which add four glass/air boundaries that the optical engineers never designed into the lens.) Exactly how much effect can range from practically nil to quite a bit. A cheap, lousy uncoated filter can really make a mess of things. A good quality, multi-coated filter will usually have minimal negative effect, but in certain situations even it can do some harm to images. It will have greater effect on a macro shot, when focusing very close, than it will on a portrait or scenic shot that's focused farther away, for example. A filter will also have more effect when there's strong specular light sources in the image, such as flare and loss of contrast. Dust on the front element of a filterless lens will have more effect at macro shooting distances, too, than it would on more distant shots (dust will also have more negative effect if not using a lens hood and allowing oblique light to strike it).
Besides, just how much "protection" do you honestly think a thin piece of glass can provide? Over the years I've probably seen as many lenses damaged by a broken filter (when glass shards gouge the front of the lens) as I've seen "protected" by one. At best, the "protection" is anyone's quess... A dropped or bumped lens might have survived just fine without any filter at all (there is no practical way to test this with every lens and every possible situation).
UV filter used to be common usage by pros because many films were overly sensitive to UV light. I used one a lot when I lived in Colorado, because UV is even stronger at high altitude. People misinterpreted the frequent use of the nearly clear filters (also Haze, Sky and Skylight) as providing some mythical kind of "protection" (which really can't be proven one way or the other)... And camera stores and filter manufacturers were only too happy to encourage this, selling filters to somehow protect that precious new lens purchase. And, older lenses (especially from the 1950s and 60s) had relatively vulnerable coatings and softer glass, so were more prone to damage from frequent cleanings (especially with the wood based paper "lens tissues" that were commonly sold and used for cleanings). Modern lenses and their coatings are much, much tougher.
In some sense, using a "protection" filter is laziness, not wanting to occasionally do a proper, careful cleaning of the lens itself. That's sort of a false expectation, anyway, though. Not too long ago I bought a used 300/4 IS from a guy who had a "protection" filter on it from day one and had bought it for use on a trip, then told me he'd not used it for four or five years, it sat in its case, in a closet for all but a few uses... Said he didn't think he had ever removed the filter. I did, and the lens was in serious need of cleaning under the filter. Both sides of the filter also needed cleaning. So, really you are ending up with more optical surfaces that will be in need of an occasional cleaning.
I'd also feel lazy not using a lens hood. The hood that came with your lens actually provides much better protection when in use... Both physically against bumps and against oblique light striking the front of the lens (or any dust specks on it). The lens cap provides great protection when the lens isn't in use.
Do I use UV filters? Yes. I have a set of them (good quality, multi-coated ones) in my camera bags ready to install if I'm shooting out in a sand storm or by the ocean when there's a lot of salt water spray in the air. But I don't leave them on my lenses 24/7/365. I only install one when it's actually needed. The horse and rider are at full gallop and turning immediately in front of me here (rider is slightly soft focused, due to shallow depth of field)... arena dirt, flying rocks and stones showered me an instant after this shot was taken...
...But my 300/2.8 IS has no filter threads up front, and would need about 120mm filter even if it did... So I just dip the lens down at the last instant and protect the front element with the deep lens hood.
Another thing. At close distances, depth of field get very shallow. You see that in your B&W macro examples, even if shot at f11 (not sure what aperture you used on them... I think you were referring to the b'ball player portrait with those exposure settings).
The problem is, with a crop sensor camera such as your 50D, you really don't want to stop down much more than f8 or f11 or you will start to lose fine detail to diffraction. You'll see it more at f16 and smaller apertures. Actually f8 is a little smaller than the most limited aperture with a 1.6X cropper (varies depending upon sensor density, probably is closer to f7.1 or so, with 50D). At f11 it might be very slightly apparent if you look very, very closely. I wouldn't use smaller aperture, though.
To familiarize yourself with diffraction, I suggest shooting a set of shots of a flat subject with a lot of fine detail, such as a weathered fence or bricks, at different apertures. Do it all on a tripod to eliminate camera movement, set your focus very carefully, set Av and an ISO that will allow you to shoot a series, start wide open and stop down one f-stop at a time all the way to f22, taking a shot at each full f-stop. Look at the images later, magnified a lot to 1:2 (50%) or greater. You will see fine detail start to disappear at f11, and more and more of it lost at smaller and smaller apertures. It's good to do this, so you know what to expect. Some shots it won't matter and you can live with it... Others, such as macros where you want absolutely every bit of detail, you need to know your limits.
So the solution isn't to stop down farther (and this is why a "full frame" camera is desirable for macro shooting, you can use somewhat smaller apertures such as f16 or, pushing it a bit f22, with less effect from diffraction).
Something relatively new with macro photography is "focus stacking" to get greater depth of field than is possible with the lens itself. It involves taking multiple shots at different points of focus, then combining them with software. See
http://www.heliconsoft.com/heliconfocus.html for more info. Unfortunately, the software to do this is relatively pricey. I'd love to experiment with it... maybe I can talk someone into getting it for me for Christmas!
Also consider that you are using this particular lens in a somewhat non-typical way. Sure, it's close focusing but really not a true macro lens, it isn't a "flat field" design. It's a zoom lens, and an excellent one at that (stop fretting!). Yes, it's quite close focusing... something that wedding photogs really appreciate for ring shots, cake details, and centerpieces at the reception. But you'd see more edge to edge sharpness out of a true macro lens, which wouldn't be a zoom (with
lots of additional optics inside... 24-70 has 16 elements in 13 groups, compared to the 100mm USM which has 12 elements in 8 groups and is probably more complex than most because it's an Internal Focus lens) and would be optimized for close focusing, among other things.
But 24-70 can make really interesting close-ups...
Raindrops on an oily surface in a parking lot, a relatively flat surface that's easier to control DOF. This isn't a super high magnification shot, used approx. 70mm setting from about 2 feet in front of the lens (which was on a 7D). No extension tubes, so near the closest focus distance of the lens.
The other thing to consider is what sportsmode hinted at... Use a tripod, if you aren't already doing so. It's almost essential for really sharp macro shots, more-so at higher magnifications. Shooting macro is like using a really long telephoto lens... it amplifies even tiny movements dramatically, which are recorded in the image as motion blur, but can look a lot like missed focus or lens softness.
Depending upon your shutter speeds, you might also need to use mirror lockup (which I think Live View will perform on your 50D, as a quick easy way rather than setting MLU in the menu or custom functions). Watch out for shutter speeds between 1/30 and 2 seconds, in particular. In this range, the slap of the mirror flipping up can cause slight blur in an image. Of course, it's worse with cameras that use bigger mirrors (full frame is more susceptible than a cropper... one of the worst cameras for mirror slap was the old Pentax 6x7, with it's huge mirror, and early ones didn't have MLU!)
You can use a remote release to trip the shutter, so that you don't touch the camera while taking the shot. Alternatively, with static subjects such as in your examples, you can use the camera's self timer even with a short delay.
And there are special focusing methods with macro shooting, too. Usually it's best to just turn off AF and focus manually. You get focus in close by turning the focus ring on the lens (actually for higher mag you use it more to set the degree of magnifcation, than for focusing, it sort of acts like a zoom instead of a focus ring). Then you move everything - the camera, lens and yourself - closer to or farhter from the subject to focus. For higher magnification shots, when using a tripod a
"focusing stage" such as this can be a handy accessory. This provides a rack & pinion focusing mechanism for more precise control moving the lens/camera closer to and farther from the subject.
If you do use AF, try Live View rather than the standard methods of focus (One Shot or AI Servo). Live View employs a completely different method of focus called Contrast Detection (using the camera's imaging sensor). This is slower, but more accurate. One Shot is more accurate than AI Servo, too, but they both use Phase Detect focus method (done by the array of AF sensors) that's faster, but a wee bit less accurate than Live View and Contrast Detect.
Finally, I don't know what post processing work you've done on those sample images, besides converting them to B&W of course. If you haven't already done so, you might need to do some sharpening to bring out the detail and make them appear more critically sharp (that's considerably more necessary with 7D and the other 18MP cameras, than with 15MP 50D... your camera uses a weaker anti-alias filter over the sensor). With shallow depth of field this can be tricky to get just right. You don't want sharpening in the OOF areas. So you might need to do selective sharpening, perhaps with layers and a mask in Photoshop (or similar).
Techniques such as these are very important when shooting higher magnification macro. It's a specialization that demands a lot more of the photographer and their gear.
Overall, looking at your images I don't think you have much to worry about. 24-70 is an excellent zoom and yours appears to be working fine. There are probably some things you can do to optimize sharpness in some ways... But it's still a zoom lens and a prime macro lens would likely be sharper in most situations.
Of course, personally I think "lens sharpness" is vastly over evaluated by a lot of people these days. They pixel peep their images at ridiculously high magnifications on their computer monitor, much larger than the image will ever actually be displayed. If you walk up too close to a Monet or other painting by one of the great masters hanging in the Louvre, all you will see is a jumble of messy brush strokes! Step back a little and enjoy the full beauty of that or your own images!
