jerryc41 Loc: Catskill Mts of NY

Good word choice.

Photocraig

I agree. SS.
That 100-400 MkI lens filled a lot of Photography and Outdoor and Sports Magazine pages in its day. For the hobbyist printing at less than 24 inches, it would take a very discerning eye and pixel peeping to see any difference.
Nice shots, Sharpie.

LFingar Loc: Claverack, NY

You didn't mention a budget number so I'll toss my hat in the ring for the EF 100-400 L II also. The EF 100-400 L I is also a very fine lens. One thing to remember about the mk I is that it is a slide zoom. You might love it or hate it. That feature was a deal breaker for many people, but that lens can be had used for a quite reasonable price. There is also Canon's EF 70-300 L. I had one. Very nice lens. Quite compact. Excellent optical qualities. Built like a tank. It also can be had for a reasonable price used. Can't use extenders with it though. At least, not Canon extenders, as I recall.

jeep_daddy Loc: Prescott AZ

Canons new 100-400 lens is very sharp and works with the 1.4x teleconverter now. You can't go wrong with this OEM lens.

GENorkus Loc: Washington Twp, Michigan

Look into a fast 70-200mm. My "goto" lens. Most of the other teles lenses have more reach but you need more light or a rediculas high ISO value.

tinplater Loc: Scottsdale, AZ

I would not completely discount the Canon EF-S 55-250 IS which is an amazingly sharp, lightweight, inexpensive lens. I also have the Canon 100-400 II, the Canon 300mm 4.0, and the 70-200 2.8. But for just having available without a lot of weight and hassle, I strongly recommend this lens which can be had for $129 refurbished from Canon!! Attached is an image taken with this lens...

(Download)

camerapapi Loc: Miami, Fl.

It would be most useful knowing your planned use of the lens you want to buy. Without this important piece of information at least I cannot make any meaningful recommendation.
A lens that has proven useful to me has been my 70-300 VR but if BIF is what I have in mind I go to my old 80-400 VR. These are Nikon made lenses but I am sure there are similar equivalent with Canon lenses.
Knowing what you plan to do with the lens is of big help when making any recommendations.

Bill Emmett Loc: Bow, New Hampshire

Hi, Don't over look the Tamron SP 150-600mm. It does need a lot of light, but really takes sharp photos. Don't forget Tamron warranties its lenses for 6 years. That includes upgrades, and updates. I use mine on both full frame, and cropped bodies.

B

Jersey guy Loc: New Joisey

Lots of good replies...thanks to everyone. "BIF"? Checked Google etc., and finding no answers that fit this discussion, I am going to make a SWAG...."scientific wild ass guess" and opine that it translates to: birds in flight. Am i right? What is so irritating to this frugal shooter is that I can probably afford the upper scale lenses but just can't bring myself to do it.

foathog Loc: Greensboro, NC

I've met PLENTY of people with breath that smells like bait.

Jersey guy Loc: New Joisey

Now now, Foathog! Be nice!

JBruce Loc: Northern MN

As an owner of the three Canon L lenses mentioned, 70-200 f4L IS, 70-300L IS and the 100-400L Mk2, if I could have only one, I would choose the 70-300L IS. It's fairly light and compact, moisture/dust resistant and sharp as either of the other two. I think it's the best all around tele-lens made, bar none. My wife uses it exclusively, except for some interior close-up work. Actually she stole it from me, so l got the 100-400 to replace it, but I most frequently carry the 70-200, lighter for my 78 years, and save the 100-400 for times when I really need the reach. [Edit] And in response to your frugal comment, check out used: they're pretty dang reasonable.

amfoto1 Loc: San Jose, Calif. USA

Since you are shooting with a Canon EF-S 15-85mm (an excellent "walk-around" lens, BTW)... You must have a Canon camera, and APS-C "crop" model that can use both EF-S and EF lenses.

You can't go far wrong with most Canon lenses. It's more a matter of how much you want to spend and how much reach you need...

First AVOID the EF 75-300mm non-IS, non-USM. You'll see it offered cheap, under $200 often. IMO, it ain't worth even that. It just isn't one of Canon better tele-zooms optically. It also lacks stabilization and uses cheaper, slower, noisier micro motor focus.

One of the most affordable is the EF-S 55-250mm IS STM, which can be found for around $300. It's a much better lens optically than the 75-300mm, plus it has both stabilization and faster, quieter, smoother STM focus drive ("stepper motor"). If you shoot video, STM is the best choice. Note: there also is a $50 cheaper EF-S 55-250mm IS with micro motor focus drive. It's equally good optically, but the focusing system is noisier, slower and not as smooth.

For action shooting, the EF 70-300mm IS USM offers good image quality and faster USM ("ultrasonic motor") focus drive. Typically USM lenses are at least 2X as fast focusing as STM, but they aren't as smooth and make a little noise that can be picked up on soundtracks, so might not be as good for video. The EF 70-300mm IS USM sells for $650 normally, but there is a $200 instant rebated offered on it right now bringing the price down to $450.

There are also two more premium versions of EF 70-300mm: There is a pro-quality "L" and a much more compact "DO". Both have IS and USM, offer top image quality, and they're in the $1350 to $1400 range. The "L" is larger though huge or all that heavy (roughly 2.3 lb., if memory serves), has additional seals for better dust and moisture resistance, is painted off white with pro-quality durability, and can optionally be fitted with a tripod mounting ring. The "DO" uses "diffractive optics" to be especially compact (a little over 1.5 lb.), making it an excellent travel lens for someone trying to keep the size and weight of their kit to a minimum. It also is a good match for some of the smaller, lighter camera bodies where some of the bigger lenses may seem nose-heavy and unbalanced (adding a vertical/battery grip to the camera body can help with that, BTW).

Yes, there also are the four EF 70-200mm lenses, all of which are L-series, pro quality durablity, painted white and sealed for dust/moisture resistance, with higher performance USM focus drive and top image quality. All of them work well with a 1.4X teleconverter, too, to be able to give an effective 280mm. There are two f2.8 (larger, heavier) and two f4 (about 2/3 the size & weight). In each of those pairings, there are IS and non-IS versions. The 70-200/2.8 IS USM Mark II is the latest, greatest and top of the line model, with extremely high image quality and costing around $2100. The 70-200/4 IS USM is the second newest, sells for about $1200, has nearly equal image quality, just not as large an aperture, so it can't blur down backgrounds as much and will be a little more limited for low light shooting. Both those use fluorite elements for very high image quality and both have newer style, three to four stop image stabilization. The other two are non-IS lenses that cost less... but I've been using IS lenses for fifteen years and really think it's worth the additional cost, especially on telephotos such as these. If you shop used, there also is the EF 70-200/2.8 IS USM "Mark I" that was discontinued a few years ago, which uses an older form of IS (2 to 3 stop) and doesn't use a fluorite element, but still has very good image quality and top performance. All the f2.8 lenses come with a tripod mounting ring. One is not included with the f4 lenses, but they optionally can be fitted with a tripod ring (Canon's costs about $160, but there are Chinese clones that cost around $50 and seem to work pretty well).

The Canon EF 300/4L IS USM ($1350) is another excellent option. I've used it a lot myself and, yes, it works quite well with a quality 1.4X teleconverter, to give you an effective 420mm f5.6 with image stabilization. It is about the weight and only slightly larger than the 70-200/2.8 zooms. Has a convenient, built in lens hood and comes with a tripod mounting ring. It is an older model that was one of the first to have IS, so uses an older version of that giving 2 to 3 stops of assistance... and that needs to be turned off manually if using the lens locked down on a tripod (most other IS lenses self-detect lack of movement and turn off IS automatically).

Some folks swear by the EF 400/5.6L USM ($1250), too. It's quite fast focusing and sharp, while still being reasonably compact. Note that it does not have IS.

Both the 300mm and 400mm are L-series, which means they are pained white and have pro-quality build/durability, extra sealing for resistance to dust & moisture. There are some advantages to primes such as the 300mm and 400mm... they are internal focusing (don't grow in length when focused), so are well-balanced all the time. They also are reasonable size and weight. And, for their reach, they cost less than zooms with similar reach and build quality.

But there also is some added flexibility working with a zoom lens. In addition to the above, Canon offers EF 100-400mm L IS USM Mark II ($2200). I've just recently been shooting with one and it's an excellent lens, with very high image quality, fast focus and the very latest image stabilization (same type used on the super teles that cost up around $10,000). The first version of this zoom, which was discontinued about a year ago, is no slouch either. One key difference, the Mark II uses a traditional two-ring design... separate rings for zooming and manual focus. The original or "Mark I" uses a push/pull design with a single ring. Some really like that... it's fast for things like Birds In Flight or air shows... but some (including me) aren't fans of the design. Personally I don't think I get as steady shots with push/pull zooms. But, that's just me. You can sometimes still find the original/Mark I brand new for around $1500, and there are a lot of used ones around for a little less. Note: I can't say about the Mark II because I haven't tried it, but the Mark I "hates" filters! It seems to "go soft" when any filter... even very high quality, multi-coated... are added to it. There's little reason to put a filter on it "for protection", anyway... it uses a very deep lens hood that does a respectable job protecting the lens from most things. The 100-400mm lenses are a bit larger than the 70-200/2.8 and 300/4... about 1 lb. heavier. They are similar in size to the 400/5.6, but about 3/4 lb. heavier.

Until recently, the EF 300/4L IS USM was Canon's closest focusing telephoto longer than 200mm. It is handy for near macro close-ups of small, shy subjects that are difficult to approach, such as butterflies. It gives roughly 0.25X or 1/4 life size magnification (most true macro lenses give 1.0X or 1:1 or full life size). However, the relatively new 100-400mm Mark II now claims these honors... not quite as close, but due to it's longer focal length it gives slightly higher magnification, around 0.31X if memory serves, which is close to 1/3 life size.

And, yes, there are various third party telezooms available. Sigma, Tamron and Tokina all make a variety to choose among. However, I personally don't see much reason to look beyond what Canon offers, which is a pretty nice range of prices and models. One thing, a Canon lens is pretty much guaranteed to work well on a future Canon camera, should you ever decide to upgrade bodies. There is no similar guarantee with third party lenses. Most are fine, but in the past a few older 3rd party lenses have not worked properly on newer Canon cameras. To be fair, in a lot of cases the manufacturer offered a fix. But in some cases the lens essentially became a paperweight. I have an older Sigma 28-75mm that works fine on EOS-3 and Elan 7 film cameras, and on DSLRs up to the 10D... but won't work on 30D and later Canon cameras. As soon as it tries to focus, it locks up the camera with an error code. It's not new or valuable enough lens to have fixed, even if it were offered and possible. My point, though, is that there is at least some additional risk of obsolescence with 3rd party lenses for use on Canon cmaeras, that is of little or no concern with Canon lenses.

So, how much reach do you need? And how much do you want to spend?

If you are in the US, the Canon USA website offers refurbished lenses at some discount.... that might be a way to stretch your money a bit. However, it's catch as catch can for refurbs.... Some lens models are available there pretty much all the time, while others only rarely show up and sell out very quickly. Refurbished can be a good way to go... but always compare with new prices. I was ready to pull the trigger on a couple refurbished camera bodies recently, but found they were actually cheaper brand new, with the Canon instant rebate program and some bundling both Canon and the retailers were offering.

Have fun shopping!

Jersey guy Loc: New Joisey

Wow! Amfoto1, that was a pretty exhaustive analysis. Thanks so much! Lotta stuff in there to digest. At this point I will just sit back and review all of these replies and investigate some of those "used" suggestions. I guess I would answer those who ask "what use do I intend for this lens" that I just want that extra reach for those occasions when I might want to be a little closer to the action...whether it be wildlife (not a lot), events like grandkids soccer games, graduations and the like. I would only lug it around when I think there might arise a photo op where I would like a little more selective DOF or to get a good closeup without a lot of cropping. As I stated at the outset, my 15-85 is so sharp that I can crop pretty tight most times when needed----assuming good exposure, no shake, etc.,---to the point where I would want just a tad more than 200 at the top of a new lens otherwise I wouldn't consider it to be much of an advantage over the present lens.

Thanks again to all, and I would still entertain any new replies.