Lens upgrade

[veritasimagery]

Okay, so I have about had it with the focusing issues I have been having with my EF-S 55-250. Sometimes it will nail the focus perfect, but other times it misses all together. It's been running about 50/50.

The question is this: what is a good replacement for this lens. Yes, I know primes are often the best way to go, and I plan on getting some, but right now getting enough primes to replace a 55-250 is not feasible. Also, since I'm shooting with a "crop" body, I know there will be differences in focal lengths outside the EF-S line. So I am wondering about third party lenses or possibly an "L" that will get me in the ball-park and perform better than this thing is.

Just did some looking on B&H and saw that Canon EF 28-135 f/3-5.6. How does this lens compare? Looking at the reviews it seems favorable, but I am still wondering about any focusing issues. Being a full-frame lens, does this put it in the same focal range of the EF-S that I have?

[inkista]

Comparing focal lengths is comparing apples to apples. 28-135mm is shorter than 55-250mm by a pretty big deal. Focal lengths don't change just because you change the size of the image plane behind the lens. It's a physical property of the lens. So, a 55-250 is 55-250 on a crop and 55-250 on a full-frame; it just shows a different field of view because of the sensor size acting sorta/kinda like cropping off the edges of the images.

I think the lenses you might want to contemplate are the EF 70-300 IS USM (non-L, the black one, not the white one), and the EF 70-200 f/4L USM (non-IS). The feature you want to look for with telephoto zooms and autofocus speed is USM. However, accuracy might be another issue, like lens or body calibration, and how you use the AF system/points.

With the 55-250 IS, is the issue of not-focusing that it doesn't focus FAST enough for a moving subject? Or that it doesn't hit a stationary subject in good light?

[RAWcop]

Don't be afraid to look at 3rd party lenses. I have a Tamron 18-200. Nice lens for all around use. There is also an 18-270 that has an image stabilization built into it, but a little more expensive. If you are looking for a fast lens that will blur the background, as mentioned above, the canon 70-200 f/4 or sigma 70-200 f/2.8 or tamron 70-200 f/2.8 would be the choice for long zoom.
I guess it all depends on what you are taking pictures of the most. Are you shooting sports, birds, portraits, etc............ ?

[veritasimagery]

Originally Posted by inkista

With the 55-250 IS, is the issue of not-focusing that it doesn't focus FAST enough for a moving subject? Or that it doesn't hit a stationary subject in good light?

It's the hitting a stationary object.

Attached are links to a couple of images.

http://www.flickr.com/photos/veritas...6984/lightbox/

http://www.flickr.com/photos/veritas...9113/lightbox/

The focus was centered on the tree, and the center of the boat. These are converted straight from the RAW file with no processing.

[veritasimagery]

Originally Posted by inkista

However, accuracy might be another issue, like lens or body calibration, and how you use the AF system/points.

That I understand, and I have learned how to use the adjusting AF points. That's the reason I am getting bugged. In both the photos I linked to, the AF point is directly over the subject. The boat is the biggest failure. The boat is centered, the center AF point was being used, good light, stationary subject. This should have been an easy one for the lens.

Never had these issues with my EF-S 18-55. Just the 55-250. Like I said, sometimes it nails it, and sometimes it just sucks.

Might I need to send it to Canon for re-calibration?

[ceremus]

Are you shooting with a tripod? Your shutter speeds are quite long for the focal lengths you're shooting at. On the trees photo your SS is at 1/6 sec, which is very difficult to handhold even with IS. On the boat shot you're at 1/60 at a focal length of 250mm, which again even with a stabilizer is pushing it when shot handheld.

If these are indeed shot handheld it could certainly explain your softness issues. A basic rule of thumb for shutter speeds is you should be using the nearest reciprocal shutter speed of your focal length. So if you're shooting at 200mm your shutter speed should be at least 1/200, at 250mm 1/250, and so on. If your subject is in motion, double your shutter speed. (This applies mostly to telephoto lengths, you're not guaranteed to get a sharp shot at 1/50 on a 50mm lens.)

A stabilized lens gives you more flexibility with this rule, but it will only take you so far.

[Hill Country Hack]

Were these shots at the extreme end of the focal length? My little 70-300 non IS kit lens gets just soft at the far ends of the focal length even on a tripod. Not as soft as your boat shot, but soft none the less if hand held no matter how fast the shutter, up to 1/500 (the soft is most likely camera shake on my end since I'm too cheap to but a monopod).

[inkista]

Don't think it's misfocus, more likely motion blur on the second shot. If you look, NOTHING in the frame is sharp, as it would be with a misfocus. Your shutter speed is 1/30s, while your focal length is 250mm. I know the advertising says it's four-stop IS, but I can only reasonably count on two most of the time.

The 1/focal_length rule of thumb is that, while handholding, you want your shutter speed to be at least 1/focal_length to mitigate camera shake blur. With an IS lens, you can go one or two stops down, so in this case, 1/250s -> 1/125s -> 1/60s. 1/30s, you might start to see blur. Some folks use the effective focal length (i.e., throw in the crop factor), or double or triple the focal length for critical sharpness. And, of course, this all supposes you've already got great handholding technique, and know how to use a steady stance, time your breathing, hold your camera, etc. Telephoto technique is different from walkaround technique is different from fast prime technique.

One more thing, the 55-250 IS is likely to sharpen up considerably if stopped down to f/8-f/16, especially at the long end of the lens. Consumer-grade lenses tend to be relatively soft wide open. Try bumping up your iso. This isn't a tiny little P&S camera sensor. Go ahead and use iso 800.

[veritasimagery]

Thanks guys.

I guess this is the learning curve moving from "P" into the manual stuff. When the camera was picking it's own settings I rarely had this issue. The same goes back to when I was shooting my old Canon film cameras in "P". Now that I am trying more creative input into it, I am running into stuff like this. The hard part is that the images don't look that soft in the LCD screen, just when I get them up on the computer, so I never know in the field if there's an issue.

As far as stance goes, I've been using my rifle skills there. The shot with the tree was done in the kneeling position with my left elbow (lens arm) propped on my left knee and hand under the lens.

[ceremus]

Good deal, man. My telephoto lens is currently a Canon 100-300mm, it's a discontinued consumer zoom, image quality isn't bad but there's no stabilizer and I found out quickly if I wanted to get any kind of consistent good quality results out of it I need to get used to shooting in manual mode.

Good luck!