[reh321]

Unfortunately yes, a Rebel will be the limiting factor in AF performance, for sure. A flagship camera is required, as well as some pretty demanding conditions, to see a difference that makes buying one or the other actually worth it.

In other words, if you're going to be shooting similar subjects and environments, then there's a good chance you shouldn't need to worry about how the lens will perform.

Considering that Pentax AF overall may not reach the level of a Canon 1DX or Nikon D4s, I'd say the point is indeed moot anyways. But if Pentax is actively working on improving their SDM autofocus, (and if they're not just collaborating / sharing that AF tech with Tamron) ...there is a small chance that in the future it could make a noticeable difference.

So, is there a practical reason for needing that level of performance? I got every picture I ever tried, including pictures of trains moving at 50mph; every picture focused quickly and correctly. I'm not sure what more I could want.

[Matthew Saville]

So, is there a practical reason for needing that level of performance? I got every picture I ever tried, including pictures of trains moving at 50mph; every picture focused quickly and correctly. I'm not sure what more I could want.

I wouldn't call some of the stuff I do "practical", maybe more along the lines of weird / envelope-pushing, (see my other post in the thread about FF) ...but yes, sometimes it is highly welcome, if not needed...

Otherwise, all telephoto sports shooters willing to use a crop-sensor would have jumped ship from Canon and Nikon to the K-3 / K-3 II, IMO, as it's a far superior camera in almost every other way to the Nikon 7xxx series and Canon 7-series.

[reh321]

I wouldn't call some of the stuff I do "practical", maybe more along the lines of weird / envelope-pushing, (see my other post in the thread about FF) ...but yes, sometimes it is highly welcome, if not needed...

Otherwise, all telephoto sports shooters willing to use a crop-sensor would have jumped ship from Canon and Nikon to the K-3 / K-3 II, IMO, as it's a far superior camera in almost every other way to the Nikon 7xxx series and Canon 7-series.

And, of course, this lens is definitely not telephoto. It appears to me that Pentax has chosen not to compete in the sports arena (if you'll pardon my pun) - that they're more interested in those shooting landscape and related areas (although I guess that would include you). They may feel that they need to concentrate on certain niches, and leave other areas to those with greater resources. I don't know whether their focusing "issues" are in the camera or the lens - although I hope they do.

[FantasticMrFox]

Otherwise, all telephoto sports shooters willing to use a crop-sensor would have jumped ship from Canon and Nikon to the K-3 / K-3 II, IMO, as it's a far superior camera in almost every other way to the Nikon 7xxx series ...

Hardly. The Nikon D7xxx series have marginally better image quality (dynamic range and high ISO) compared to the Pentax Kx series, and definitely a better AF module, especially for AF.C. The K3 (II) has its strength, but it is hardly 'far superior' to the Nikon D7100/D7200.

[y0chang]

I've used a 7100, and the 7100 has worse ergonomics, a pathetic raw buffer, and it feels like a hunk of plastic compared to my k5. The af module is pretty advanced, but other than tracking focus, I didn't notice that much difference. Granted this was with a sigma 150-500mm and so YMMV with a ultra fast 1st party lens like a nikon 70-200mm

[ElJamoquio]

Never used a 7100.

The D7000 was much better at AF than my K-5. The K-5 was better at all other respects.

[normhead]

I think it's pretty much decided, if AF is your only consideration, a Nikon D7xxx series or D750 is your way to go. For many of us, the picture we get is more important than how fast the camera focussed, so Pentax will do. It's just a question of do you really want to change systems every time one system is marginally better than another at something. It has to be a pretty major difference before it's worth the cost of changing brands.

It's been demonstrated how much better the D750 is than an K-3 for tracking a subject coming towards you at high speed. The only images I've taken like that in the last 2 years were test images for that thread. Honestly, I'm not switching for that. And similarly, if I owned that system, I can't think of anything that would inspire me to switch to Pentax. The simple fact is, there are a lot of cameras out there that do pretty much the same thing.

All the lenses that made me stay with Pentax when i went digital, my ex took with her after the divorce. Life is cruel.

[cali92rs]

All the lenses that made me stay with Pentax when i went digital, my ex took with her after the divorce. Life is cruel.

Marriage is grand...
Divorce is a hundred grand.

[Matthew Saville]

Hardly. The Nikon D7xxx series have marginally better image quality (dynamic range and high ISO) compared to the Pentax Kx series, and definitely a better AF module, especially for AF.C. The K3 (II) has its strength, but it is hardly 'far superior' to the Nikon D7100/D7200.

Hence, my use of the phrasing "in almost every way"

Aside from the marginal difference in image quality, (same sensor source, sorta) and the debatable superiority of Nikon's general interface / customizability, physically speaking the K-3 II is a more robust, flagship-like camera than the Nikon by a long shot, and the 7D mk2 by enough of a margin that anybody not highly concerned about AF or an existing stable of lenses should find the decision to still be an easy one.

Some of that is fact, some of it is opinion, but either way my original point was actually just that these differences aren't significant enough to be noticed by the average shooter. You've got to be quite an envelope-pusher for the differences to sway you towards any one camera or another.

=Matt=

[thibs]

Aside from the marginal difference in image quality, (same sensor source, sorta) and the debatable superiority of Nikon's general interface / customizability, physically speaking the K-3 II is a more robust, flagship-like camera than the Nikon by a long shot, and the 7D mk2 by enough of a margin that anybody not highly concerned about AF or an existing stable of lenses should find the decision to still be an easy one.

Nikon's interface superiority?
I dunno about their high end cams but D3xxx to D7000 (7100/7200 I dunno), their interface laughable, badly designed and without any apparent logic (to me).
Yes is this strongly subjective

I hope (for the owners) their D700+ cams are better thought.

[Zygonyx]

I would rather speek about general ergonomy, than interface.
Simple and efficient versus complex and sometimes innapropriate...

[Matthew Saville]

Nikon's interface superiority?
I dunno about their high end cams but D3xxx to D7000 (7100/7200 I dunno), their interface laughable, badly designed and without any apparent logic (to me).
Yes is this strongly subjective

I hope (for the owners) their D700+ cams are better thought.

Yes, I had this exact discussion here when I tested / reviewed the K-3. I found its interface nice, and with familiarity it really does work well. However I still found it not as customizable and adaptable as Nikon's prosumer and pro cameras. Nikon puts more effort into allowing advanced customization of both menus and physical buttons, in areas that most all others do not. (Including Canon, by the way)

Part of this is obviously entirely subjective, because it does have a lot to do with familiarity, and how people's brains / shooting habits are wired. I'll be the first to admit that.

However, I maintain that it is indeed possible for one camera / system's customizability and interface to actually, quantitatively be at an advantage over another, definitely beyond the ambiguity of personal preference.

For example on prosumer Nikons, face-detection is built into the image playback so with the twirl of a command dial it can scroll from face to face at 100% zoom, allowing portrait photographers to verify sharpness / blinking with incredible speed that saves quite a few seconds per click while on the job.

TLDR; I'm sure that practically every photographer who has only ever fully experienced a single system is probably quite happy with that one system, and considers it highly usable and practical. However myself as someone who makes a (partial) living by testing and reviewing MANY systems, I'm positive that it is possible to tally up advantages and disadvantages, and discover that they do indeed favor one system over another. Does this mean I'd refuse to use any system other than the one I conclude is the best? Not at all. If the Pentax full-frame camera interface is good enough, I'll gladly dump my Nikon D750 in favor of it. However at present, I have my doubts. I'll buy the Pentax FF body immediately when it comes out, but I may decide to only use it for adventure, landscape, and astro-landscape photography, and continue to use my D750 for weddings. Call it mere familiarity and comfort, if you'd like to, but I'll approach the experience with as much of an open mind as I possibly can and will definitely share my opinion when I have enough experience to form it...

=Matt=

[bxf]

For example on prosumer Nikons, face-detection is built into the image playback so with the twirl of a command dial it can scroll from face to face at 100% zoom, allowing portrait photographers to verify sharpness / blinking with incredible speed

Oooh, I wouldn't mind this one. Please, Ricoh.

[Kharan]

Nikon's interface superiority?
I dunno about their high end cams but D3xxx to D7000 (7100/7200 I dunno), their interface laughable, badly designed and without any apparent logic (to me).
Yes is this strongly subjective

I hope (for the owners) their D700+ cams are better thought.

I completely agree! Nikon cameras (of all types) are the only ones that always leave me staring at them at a loss. I find their operation a nightmare. Of course, I'm sure I could adapt to them in time, but it seems like a difficult proposition, at least from my limited experience with them.

I'm a Canon guy when it comes to interfaces. I find their layouts the best, followed by Panasonic and then Pentax. I don't have nearly as much trouble with Sony cams as many other people, I think their interface is fairly straightforward. Olympus and Fuji don't gel with me, but they're not bad.

[Matthew Saville]

I completely agree! Nikon cameras (of all types) are the only ones that always leave me staring at them at a loss. I find their operation a nightmare. Of course, I'm sure I could adapt to them in time, but it seems like a difficult proposition, at least from my limited experience with them.

I'm a Canon guy when it comes to interfaces. I find their layouts the best, followed by Panasonic and then Pentax. I don't have nearly as much trouble with Sony cams as many other people, I think their interface is fairly straightforward. Olympus and Fuji don't gel with me, but they're not bad.

The "limited experience with them" is key, IMO. I've had the good fortune to be able to use both Canon and Nikon DSLRs for over a decade now, getting familiar with practically every lineup of camera they make from beginner to flagship.

Once you can wrap your mind around how different the interfaces are, you begin to notice the true perks (and disadvantages) of each. As another example, Nikon didn't offer custom settings banks in the proper way until very recently; they previously had two entirely separate menu banks that were very annoying for some, but highly practical for others. I enjoyed being able to change a handful of settings all at once, but not others. (So for example I could go from shooting 12-bit compressed RAW for high-volume sports / weddings to shooting 14-bit lossless RAW, with a few other settings tweaks as well, for serious landscapes, without digging through a bunch of different menu items...)

While daunting, the Nikon interface has offered what I feel is the most generously customizable menu section possible. Canon still only offers one single page of custom menu items, Sony only offers two rows of custom menu items, and AFAIK Pentax doesn't even have something truly equivalent; although they do have some customizable interface areas that are similar. Nikon offers a custom menu that is 18 items long, or two and a half pages worth of custom menu items. That is enough for almost any OCD photographer to create a personal menu so thorough that they practically never need to dig through any of the other menus, ever!

Each brand system has it's own perks that I wish others would adopt. Maybe some are patented and will simply never find their way into other cameras. I highly doubt Nikon or Canon will EVER be able to do something like astro-tracing, for example, which is one of the reasons I'm switching to Pentax for my astro-landscape photography adventures. (That, and the incredible array of highly weather-sealed products, right down to the more affordable / beginner gear!)

=Matt=