Help with a "walk-around ...

[DP]

Own a Canon 40D with 70-200 2.8 L and 17-40 1:4 L lenses.  Nearing 80 years, in addition to these would like a reasonably sharp, compact /light walk-around.  Considering Tamron 28-300, 18-250, 18-270, or Canon 70-300 DO.  Or something else?  Your thoughts appreciated.   DP

[Bob Atkins]

Why not the Canon EF-S 17-85/3/5-5.6IS USM? It covers a useful range, it's image stabilized, has a true ring USM focusing motor which gives fast and silent foicusing, and it's fairly small and light. Image quality is quite good.

If you want an extended zoom range, I'd take a look at the Tamron 18-270mm f/3.5-6.3 Di II VC. It has Tamron's version of image stabilization. Youd perhaps be sacrificing some image quality for the extended zoom range, but there's no denying that having just one lens to cover the whole 18-270mm range is very convenient.

[DP]

This is helpful !  If I go for a more extended range than the 17-85 provides, your suggestion of the Tamron 18-270 is probably the answer for me.  While the Tamron 18-250 lacks VC, is there any trade off for the 18-250 being more compact for travel even though it lacks stabilization?  Or does VC trump size, being there's not a huge dimensional difference in the two lenses?  I sort of stumbled on your forums ... what a benefit!
                                                            DP

[Bob Atkins]

Personally, I wouldn't buy a telephoto zoom for "walkaround" use without some sort of image stabilization, since these lenses tend to be pretty slow at the long end (f5.6 or f6.3). The slowest shutter speed you could normally use to get a sharp image in the 250-300mm range would be around 1/400s without stabilization. Most stabilization systems will allow you to use a shutter speed of 1/100s or slower and still get sharp images, even when fully zoomed out.

I'd definitly pick the VC lens over the non stabilized version.

[DP]

Your advice makes a great deal of sense to me, which I greatly appreciate!  Thank you ...       DP

[yayas]

One question Bob,
If I remember correctly, you said the autofocus only works on aperture of 5.6 or bigger.
At the Tamron's longest end, where the max aperture is 6.3, how does the AF work?

Thanks

[Bob Atkins]

They fake it somehow! I'm not 100% of the technical details, but for many years the 3rd party lens makers have produced lenses which are f6.3 at the long end of telephoto zooms and AF works OK. I presume that they use some electronic means to fool the camera into thinking the lens is actually f5.6. Sigma actually had an f7.2 lens which seemed to AF OK most of the time.

All Canon lenses are f5.6 or faster, even at maximum zoom. The f5.6 limit is simply what Canon decided was a safe cutoff point. In fact f6.3 (and even f7.2) is normally fast enough for the AF system to operate, but Canon like to "play it safe" and use an f5.6 limit.

[KeithB]

Also, f6.3 on a telephoto still has a pretty small "acceptable focus" range compared to a wide angle.  I would guess that the actual aperature limit (which is probably pretty loose anyway - much like IS effectiveness)  for autofocus is a function of the focal length.  Longer focal lengths can get by with larger apertures.

[yayas]

Thanks,
a new knowledge for me.

[dppollet]

Of course it depends upon the walk around situation.  I have found that Canon’s EF 100-400mm f/4.5-5.6L IS USM zoom is ideal in many situations, especially at theme parks and zoos where you are often more than 50 feet away from the subject. 

Alternatively, I have also found that Canon’s EF 24mm f/2.8 prime lens to be ideal when the subject is within 15 feet.  I recently used one to photograph a California mission and a ghost town and obtained excellent results. 

However, if you want the convenience of a zoom, then I would recommend the EF 24-105mm f/4L IS USM because it has IS, an L model zoom generally provides performance that compares to that of primes, and finally, it complements the range of the EF 70-200mm f/2.8L USM that you already have. 

[KeithB]

"I have found that Canon’s EF 100-400mm f/4.5-5.6L IS USM zoom is ideal in many situations, especially at theme parks and zoos where you are often more than 50 feet away from the subject. "

This is fine as long as you don't wan't to take pictures of the folks with you, but I find that my 70-300 at 70 mm is way to narrow for pictures - in a petting zoo for example - where you want to stay reasonably close to the action.  In this case, I have to switch to the 17-85.