bud 77 Loc: Long Beach, WA

Thanks blurryeyed, I will have an opportunity to shoot some next week and will back down to f11 as you suggested and see what I get. I like to get the max depth of field but That should work. bud

Blurryeyed Loc: NC Mountains.

Read about Hyperfocus, it is very interesting and surprising, I often carry an old manual 35mm prime that is very sharp, I know that set at f/8 and focused about 15 feet out I don't have to worry about focusing my camera unless the subject is very close to me. That linked article may be very helpful, I am sure that there may be better articles out there if you find the subject interesting and useful, play with the calculators to help you understand your lens.

bud 77 Loc: Long Beach, WA

I do use a depth of field calculator and turn off IS and auto focus and set focus point at about 10 feet and that works for me when I am shooting landscapes with a tripod. Thank you so much for taking the time to help. I retired about two years ago and have been studying photography as a hobby.

rocketride Loc: Upstate NY

A perfectly corrected optical system will always be sharpest (have its highest resolution) wide open. The theoretical resolution of an optical system depends on exactly two things; the wavelength of the light being imaged and the angular subtent of the light cone on its shorter conjugate (which is generally the distance between the lens and the image). The lower the f# of the lens, the greater that angular subtent and the smaller the diffraction pattern formed as the image of a point source. This scales linearly-- an f/2 lens can theoretically resolve point sources half as far apart (in angle) as an f/4 lens can.

Theoretical resolution also varies with wavelength. The shorter the wavelength, the smaller the diffraction pattern will theoretically be.

Few photo lenses are so well corrected that aberrations (which decrease with stopping down) will not overwhelm diffraction until the lens is stopped down a stop or two. The EF-S 10-18 at 15mm is apparently one of them.

camerapapi Loc: Miami, Fl.

This is a great idea. I was about to say that each of us needs to determine how much wide we want to go. In my particular case my 12-24 f4 Nikkor is all I need.
I do not believe it is a good idea to use your wide angle at f22 where surely diffraction will degrade the image to some extent. Crop bodies have a large depth of field in comparison to full frame.
If in need of a wide angle try to establish first how wide do you usually go with your photography, it will make your selection easier.

dsmeltz Loc: Philadelphia

DOF calculations are independant of sensor size. Given the same apeture, focal length and distance from subject the DOF is the same on a crop, FF or MF.

rocketride Loc: Upstate NY

But DOF is not independent of pixel size. Smaller pixels mean less leniency-- i.e., the "blur circle" has to be smaller for blur not to be visible.

wj cody Loc: springfield illinois

if you are really concerned with your digital images and want the best lens for landscapes, and intend on making large prints of your work, the 24mm or 25mm wide angles, being prime lenses, will ALWAYS deliver better results than ANY zoom lens across all apertures.

ANY zoom lens is an optical compromise between its widest and longest range. a prime wide angle lens is the most difficult, optically, to manufacture. any faults in its construction are glaring in the print results. to further degrade at every aperture, the wide angle optic by compromising it with a zoom lens, of any make, is rather pointless.

if convenience is your major objective, then, by all means, go for a zoom lens.

speters Loc: Grangeville/Idaho

Pointless? They are the best selling type of lenses world wide, for a long time and for a reason!

wj cody Loc: springfield illinois

i agree, and more kias are sold than volvos. which would you rather get in an accident with?

of course they sell more of them. after all, think of the "convenience" of only one lens. oh, and they are lighter, and you don't have to carry anything else. along with your digital imaging device, it will do everything for you - couldn't get luckier, i imagine.

speters Loc: Grangeville/Idaho

There are plenty of "zoom-Volvos" out there, some of them better optically then primes!

amfoto1 Loc: San Jose, Calif. USA

First things first... the EF-S 15-85mm is usually considered a darned sharp lens. I've seen very few complaints about it being soft.

Do you have a "protection" filter on it? If so, try some shots without it.

Also, [I]stop using f22[/u]! Some of the softness you are seeing is due to diffraction. The optimum aperture on a 50D (APS-C, 15MP camera) is about f8 for an 8x10/8x12 print. Actually you probably wouldn't notice much diffraction at f11 and larger print sizes.... but at f16 and especially f22, you will see a lot of it occurring. Diffraction "robs" the image of fine detail and makes it look sort of plasticky or soft.

Diffraction is sensor size dependent in that it becomes more obvious the more an original capture is enlarged. For example, an APS-C sensor (such as your 50D's) needs more enlargement to make an 8x10/8x12 print, than does a full frame sensor (such as 5D series). So diffraction will be more obvious with the smaller sensor camera (thus you need to limit how small an aperture you use more with the APS-C camera). I know with my 18MP 7D the DLA (Diffraction Limited Aperture, at 8x10) is f7.1... though I'll use f8 and f11 without much concern. With my 21MP 5D Mark II, the DLA is f10... and I use f11, f16 pretty freely.

Also, if making 13x19 or 16x24 or larger prints, diffraction can become more obvious, but is typically offset to some extent by greater viewing distances.

In addition to the above link regarding hyperfocal focusing distances... the same site has a good explanation of diffraction, if you want more info: http://www.cambridgeincolour.com/tutorials/diffraction-photography.htm

You should get or make a depth of field calculator and use it (here's one online: http://dofmaster.com/dofjs.html).

Then learn to use hyperfocal focusing distances.

For example, if you set your lens to 15mm and f11, focus the lens to 5 feet, everything from 2 feet to infinity will be in focus! At f8 instead, everything from 2.5 feet to infinity is in focus.

So you don't really need to use f22! It's just costing you image quality.

I also am not sure if you should be turning off IS. Some Canon lenses do not require it... and in fact can correct for fine in-camera vibrations such as mirror slap/shutter shake. I don't know about the 15-85mm in particular... whether its IS needs to be turned off or not. But you can easily test it yourself. Does the IS cause movement, when the camera and lens are locked down on a tripod and there is no movement? It's sort of like a feedback loop and you can see it occurring in the viewfinder. If so, turn IS off (no harm will be done to camera or lens). If not, leave IS on... it might help with fine vibrations, even on a tripod.

Now, do you still need another lens? If you want something wider, Canon EF-S 10-22mm USM is one of the best in it's class. The new EF-S 10-18mm IS STM is a cheaper alternative that's getting some pretty good reviews.

The Tokina 11-16/2.8 rivals the Canon 10-22mm for sharpness and is the only f2.8 zoom in the ultrawide category. However, it's more prone to flare... and to get f2.8 you have to accept that very narrow range of focal lengths. f2.8 is not very commonly needed on ultrawides anyway, other than perhaps by photojournalists and astrophotographers. If you want ridiculously wide, you might want to look at the Sigma 8-16mm... the widest available, short of a fisheye lens, but also has some relatively strong distortions.

There simply aren't many prime lenses that are particularly wide on crop sensor cameras. Rokinon 14mm (also sold as Samyang, Bower, Vivitar 13mm, and more) is one of the few that's affordable... manual focus and manual aperture... sharp, but has significant distortion (moustache type). Canon 14/2.8L II is very pricey. So is the Zeiss ZE 15mm.

It's only moderately wide on a crop sensor camera, but one prime I use and like is Canon EF 20/2.8. In fact, on a crop camera the "best" part of this lens is used (on full frame it shows more softness in the corners and stronger distortion effects at the edges.

This was shot with that 20/2.8, at f5.6, on 50D (with B+W Kaësemann C-Pol filter)...


Hopefully the crop/enlargement gives you some idea, but Internet resolutions really don't do it justice. When printed 11x14 or larger, there is sharp detail right to the edge, using this lens on a crop camera. Actually this lens on a full frame camera really ain't bad, either (5DII, f11, same filter)...

wj cody Loc: springfield illinois

sorry, but they're not. it's simply a matter of optical configurations and lens barrel tolerances.

rocketride Loc: Upstate NY

Lens barrel tolerances? As opposed to optical formulas? There's at least one zoom lens that has been discussed on this thread that at one focal length was sharpest wide open. (I.e., diffraction was the limiting factor to resolution at all f-numbers.) Unless you can name an APS-C prime lens of the same focal length that matches this performance, your assertion that prime lenses are categorically optically better than zooms at all times and at all places is blown straight out of the water. Any given well-made prime is probably going to be sharper than any given well-made zoom, but there are exceptions. . .

speters Loc: Grangeville/Idaho

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