[Danaher Dempsey]

I bought a Nikon V1 when they were blowing them out some years ago.
$400 for body and 10-30mm zoom and 30-110mm zoom (crop factor 2.7)

That camera has incredible focus speed and accuracy.
With extension tubes it maybe the best tool for extreme macro close ups due to amazing focusing.

It also does fairly well with video. With an older 1" sensor ... not good in low light.

You might take a look at the current Nikon J5 with excellent modern sensor
with 10-30 zoom (35mm equivalent 27-81mm) => $500

with 10-30 zoom and 30-110 zoom (equivalent 81-297mm) => $750

or with 10-100 zoom (equivalent 27mm-270mm) => $1050

Check out Thomas Stirr Photography for amazing macro photos.
Thomas Stirr Photography -

Nikon has decided to cancel their new 1" sensor DL camera, which could mean increased emphasis on Nikon 1 system.

I bought a Nikon 1 system power zoom made for video and it worked very well.
Nikon 1 NIKKOR 10-100mm f/4.5-5.6 AS VR IF CX HRI ED Lens (PD-ZOOM)
which is about $300 used today.

---------- Post added 02-15-17 at 05:14 AM ----------

For more on selecting a Nikon 1 camera body =>
Factors to consider when choosing a Nikon 1 body - Thomas Stirr Photography

and Macro photos =>
Macro Archives - Thomas Stirr Photography

[johnmflores]

My Panasonic LX-100 is incredible. The image quality is top notch, and it is the most responsive camera I've used in years. Focus is ridiculously fast. It's a non-interchangeable lens camera with an M4/3 sensor. My only complaint is that it's just a standard (but fast! f/1.7-2.8) 24-70 equivalent zoom. I wouldn't want it as my only camera. But as something to have for family gatherings and any other time when packing a bag of lenses isn't practical it is perfect. I've even taken it in the bag as an emergency backup on professional shoots. I've never needed to use it but I wouldn't be the least bit concerned about the quality I would get from it if I ever had to.

This might be my recommendation if it fits the budget. It is smaller than even the K-x and would be easy enough to always have in the bag. The K-x can still be used outdoors in good light with a longer zoom lens.

[normhead]

The K-x was a pretty good low light camera. So in that sense going to a smaller sensor is a step backwards , not an upgrade.

Something a lot of people are fastidiously ignoring.

What builds on the features of a K-x? Directly, a K-30. Same basic abilities, but better in every regard, added an extra element to correct the tungsten light issue and increased resolution, without giving up any of the features that made the K-x a great camera.

The K-3 and every camera after built on those improvements.

Once you start horse trading, giving up features that made the K-x what it was, you might as well start from scratch and just buy any camera.

Giving up low light capability for a camera that will see indoor use? People are recommending that? Sane people?

My wife went from a K-x to a K-5, she's still using it. After using a K-x a k-5 will blow you away. Anything more modern even more so.

Staying with Pentax is going to give you everything you had with the K-x you used for 7 years, only better. Changing brands, you're going to give up some Pentax magic.

Amazing how many folks who post in threads like this, don't even understand what that is.

If size is the thing you like most about the K-x, you want a K-S1. You don't need to migrate to a whole new system to get a smaller camera, despite the implications of some of the posters above.

[johnmflores]

The K-x was a pretty good low light camera. So in that sense going to a smaller sensor is a step backwards , not an upgrade.

Something a lot of people are fastidiously ignoring.

What builds on the features of a K-x? Directly, a K-30. Same basic abilities, but better in every regard, added an extra element to correct the tungsten light issue and increased resolution, without giving up any of the features that made the K-x a great camera.

The K-3 and every camera after built on those improvements.

Once you start horse trading, giving up features that made the K-x what it was, you might as well start from scratch and just buy any camera.

Giving up low light capability for a camera that will see indoor use? People are recommending that? Sane people?

My wife went from a K-x to a K-5, she's still using it. After using a K-x a k-5 will blow you away. Anything more modern even more so.

Staying with Pentax is going to give you everything you had with the K-x you used for 7 years, only better. Changing brands, you're going to give up some Pentax magic.

K-x had very good low light image quality. Not very good low light AF and OP mentioned not knowing what part of the image the K-x was focusing on and missing focus on fast-moving children.

A 1" sensor like the LX100 will have faster AF, face-detect, visual cues on the display, a faster lens, and deeper DOF thanks to the smaller sensor. Will it have more noise than the K-x? Under certain circumstances, perhaps, but a noisy in-focus shot is more valuable than a less-noisy out-of-focus shot.

And I'd hazard a guess that an LX100 will have better AF than even a K-5.

[VoiceOfReason]

The K-x was a pretty good low light camera. So in that sense going to a smaller sensor is a step backwards , not an upgrade.

Something a lot of people are fastidiously ignoring.

What builds on the features of a K-x? Directly, a K-30. Same basic abilities, but better in every regard, added an extra element to correct the tungsten light issue and increased resolution, without giving up any of the features that made the K-x a great camera.

The K-3 and every camera after built on those improvements.

Once you start horse trading, giving up features that made the K-x what it was, you might as well start from scratch and just buy any camera.

Giving up low light capability for a camera that will see indoor use? People are recommending that? Sane people?

My wife went from a K-x to a K-5, she's still using it. After using a K-x a k-5 will blow you away. Anything more modern even more so.

Staying with Pentax is going to give you everything you had with the K-x you used for 7 years, only better. Changing brands, you're going to give up some Pentax magic.

Amazing how many folks who post in threads like this, don't even understand what that is.

If size is the thing you like most about the K-x, you want a K-S1. You don't need to migrate to a whole new system to get a smaller camera, despite the implications of some of the posters above.

Yeah, people dismiss the KS1, but they can be had cheap and the image quality is quite good. I bought some as Christmas presents for people in 2015, and I even got to play with one of them some. It was small, responsive, and was to me a direct descendant of the Kx.

[normhead]

And I'd hazard a guess that an LX100 will have better AF than even a K-5.

I guess the whole part about missing the unique things he likes about Pentax is lost in this answer. Funny how people claim to be answering post, but miss the main point. There, I clarified it.

Unless you're going to tell me an LX100 has everything a K-S! has, and more.

[johnmflores]

I guess the whole part about missing the unique things he likes about Pentax is lost in this answer. Funny how people claim to be answering post, but miss the main point. There, I clarified it.

Unless you're going to tell me an LX100 has everything a K-S! has, and more.

I think that the OP's desire to get sharp, in-focus, shots of fast-moving children
AND stay within the Pentax ecosystem
AND stay within the stated budget
AND do all of that without a lot of investment in time or practice
Is a tough challenge.

Could the K-S1 do it? Perhaps, but even the K-3 struggles tracking moving children in poor indoor light and requires some patience and skill to get the shot. Otherwise, the KS-1 is likely a fine camera that would fit in the budget. If the OP would invest the time (and perhaps find a fast prime too if they don't already have one) then maybe it will work.

But another way to achieve the OP's stated goal is to give up the brand loyalty. And my suggestion is to use a camera that has a fast lens and good face-detect autofocus and give up the Pentax ecosystem. Simple as that.

[clackers]

And my suggestion is to use a camera that has a fast lens and good face-detect autofocus and give up the Pentax ecosystem. Simple as that.

Face detection will rely on slower focus from the sensor readout at some point, John, not good in low light.

PDAF is the best in low light.

I would want a big sensor, too, if shutter speed to capture the kids is being traded for ISO.

[normhead]

And I'm not going to go with that until I see a side by side comparison. What often happens in these kinds of situations is, folks under-estimate Pentax, people over-estimate the competition, really bad advice gets handed out.

Have you guys even done taking fast children in bad light on these small sensor systems? If there' no pictures it didn't happen, if there are no side by side examples proving you tried two systems head to head, it didn't happen.

And I have to ask, what systems don't struggle tracking children in poor indoor light?

Say you tried it with a K-3 and it struggled, how do you know something else was better.

The biggest problem I had with my K-1 was keeping up panning. It had nothing to do with the AF when I kept the kinds within the selected AF points. I've got gymnasts running straight at me. I'm not sure what could be more difficult. No light 3200 ISO to get 100s at ƒ1.7. What's the problem?

[johnmflores]

And I'm not going to go with that until I see a side by side comparison. What often happens in these kinds of situations is, folks under-estimate Pentax, people over-estimate the competition, really bad advice gets handed out.

Have you guys even done taking fast children in bad light on these small sensor systems? If there' no pictures it didn't happen, if there are no side by side examples proving you tried two systems head to head, it didn't happen.

I know full well the capabilities of Pentax AF up to the K-3. I've managed to capture action in all sorts of light.


Sandy aboard his trusty Yamaha FJR in VT by John Flores, on Flickr


Glen Canyon National Recreational Area, UT by John Flores, on Flickr


#56A has the bike crossed up as he exits the turn by John Flores, on Flickr


#25 is crossed up by John Flores, on Flickr

To suggest that I underestimate the capabilities of Pentax is frankly ludicrous:


Pentax K-5 shoots the cover of RoadRUNNER Magazine, Feb 2013 issue. by John Flores, on Flickr


Pentax used for RoadRUNNER story. by John Flores, on Flickr

The untold story of these shots is that it took considerable work to get them because I was working within the limitations of Pentax AF.

These days I find myself reaching for my Panasonic Lumix GX85 camera more and more because its DFD AF is, in my experience, faster and more reliable than Pentax AF (up to my experience with the K-3, at least), allowing me to get action shots in low light with a higher hit rate and less effort:


Set the Pick by John Flores, on Flickr


Foul! by John Flores, on Flickr

The icing on the cake is 4K Photo mode which is great for youth sports:


My great nephew catching some serious air at his first taekwondo tournament. by John Flores, on Flickr


Windup (processed grab) by John Flores, on Flickr

You are basically shooting 8 megapickle JPGs at 30 frames per second for up to 3 seconds so you can record a short burst and pull the photo that you want. Image quality is not comparable to a 16 megapickle Pentax DNG but more than good enough for capturing family moments and sharing them online.

Here's a video showing how Panasonic DFD AF is working hard to get a shot:

You Tube

You Tube

I recommended the LX100 because it has 4K Photo and might be well-suited to the OP's needs.

So go ahead and wait for someone to do the side-by-side comparisons. I won't bother because I've already seen in real life situations how good the Panasonic is.

[mikesbike]

Most interchangeable lens cameras these days are fairly small compared to years ago. Yet smaller size in a camera is of more importance for portability, for longer treks or pocketability for events, museums, etc. There are quality tradeoffs in going to a smaller sensor, but sometimes not enough to be noticeable. One is that smaller sensors tend to make more noise at higher ISO and lose more detail when noise reduction kicks in.

When changing systems one has to consider the cost of a whole new lens system as well. Some systems other than Pentax, Nikon, Canon, etc. have shown better performance for AF tracking of moving subjects. I sometimes shoot indoor action sports, wrestling, hockey, etc. but still stay with Pentax. I have had good success with it. But I come from years of film use where you make every shot count. It is really about learning control over the AF, using the AF button, half press, etc. with a fast eye to nail your shot, rather than using continuous AF and burst shooting (spray and pray) to "let the camera do it" with a ton of images to sort through afterwards.

For indoor action a fast lens is most important to achieve the shutter speed you need to stop action sufficiently. For this kind of photography I use a constant aperture f/2.8 zoom lens. I now shoot with a K-5 IIs, which has very good low light and excellent detail performance. You'd be better off keeping your K-x and your other general purpose lenses, and putting your money towards such a lens. Better yet, spend $100 more than the K-S2 and get a K-70, which has demonstrated outstanding high-ISO low light capability while preserving very good detail. If you can get excellent results at ISO 6400, f/4 is like f/2.8 at ISO 3200, and ISO 3200 is like ISO 1600 or even ISO 800 with most other cameras. The higher ISO quality will give you 2x or even 4x the shutter speed. If you can also buy one f/2.8 zoom lens with the K-70, even better yet. Keep your current lenses for general use when you don't need that speed. The f/2.8 lens also allows better control over background blur for portrait use. But such lenses cost more and are larger.