user19085: I'm interested in shooting slow-motion videos of sports (eg. ping-pong, badminton; for analysis and such). After trying an iPhone camera I wish to get something higher quality/more crisp (ideally 1080p@240fps).
However, finding something decent at an affordable price-tag seems to be rather difficult. hispeedcams.com is a quite good source for this purpose. Here are some notable finds.
research
rather professional solutions (too expensive)

RED RAVEN "[...] 4.5K Full Format (FF) at up to 120 fps, or in 2K FF at 240 fps, [...]" (at $8,950.00 (USD), €9,030.00 (EUR), £7,970.00 (GBP))
Panasonic AG-DVX200 "120-fps Variable Frame Rate" ($3,795.00)
SONY NEX FS700 "120fps at 4K" ($3,499.00)

dedicated high speed cameras (more than needed)

edgertronic SC1 "- 701 fps @ 720p: Color 8GB DDR3 Install IR Filter - 400-675nm response" ($5,495.00)
chronos 1.4 "1,057fps [at] 1280x1024" (2,999.00$

action-cams (too limited): ("240fps at 720p and 120fps at [...] 1080p")

Sony FDR-X3000 ($348.00)
GoPro Hero 5 Black ($399.00)
Yi 4k+ ($339.98)

DSLM/MILC (which would also be nice as default photo cameras but don't have a optical TTL view finder)

Panasonic GH5 apparently 1080p@180fps (€ 1.999,00)
Sony A6500 1080p@120fps ($1,399.99)

It would be nice to have something more versatile than action-cams, but less expensive than those professional devices. As I don't want to shoot slow-motion only, cameras specially designed for that aren't really what I am looking for either.
This leads to the (still quite expensive) GH5 (or similar DSLM) and also to a few
questions:

What should I look for in gear for a beginner?
Is there something (DSLRs/DSLMs) in between (regarding price) GH5 and action-cams (similar to a6500) supporting slowmo ?

Some specifications mention that high-speed capture is only available for a few seconds

Is there always a maximum on how long can I capture slowmo if it is not noted?
If a camera is advertised with (eg.) 8sec 1000fps, at which rate could it record permanently then ?


note:
I have asked for DSLRs on photography already with comments mentioning the GH5 only - I can remove this partial question if it is not fitting
I have split off the SDI part-question here.

user14504: You may want to look into Sony's camcorder line (even legacy; like the NX5U). 
The NX5U and I think even the FX1000 (which is an HDV Tape Format and can be had used on a place like ebay for under $1000) could do bursts of full 1080p 240+ for a "limited time". 
If I remember correctly the FX1000 by sony could do 240 frames at for 10 seconds. It would buffer the video into internal memory; then queue the tape; then record to tape when the 10 seconds was up. 
It was limited in terms of it's usefulness; but it sounds like based of what you want to use the slow motion capture for; it may be worth looking into to. 
Burst cameras (even the iPhone now does this); will give you a higher frame rate, with limited record time for a much lower price than say going the RED route or Phantom Route. 
Or you could rent a RED, RED Epic's will do 480FPS at 1K; and they can be rented cheap; as they are everywhere... and sit on the shelf most day's of the week by people who own them. 

user2836: There isn't really any magic bullet in high speed photography.  High speed photography is difficult because of the amount of data involved and the sensitivity necessary for the sensor.  Both of these factors combine to drive up the cost of all portions of the camera to do it well.  You can either sacrifice quality (which the iPhone does) or you can sacrifice affordability.
The higher the frame rate gets, the less time is available to expose each frame and thus the more sensitive it needs to be.  This makes the cost of the sensor higher.  Additionally, that data needs to be transferred off the sensor more quickly, which means more expensive sensor, it needs to be processed more quickly, which means more expensive electronics and it needs to be stored more quickly, which involves more expensive media.
Some cameras try to save on the cost and maximize quality by putting the money in to a faster sensor, but then putting a limited amount of high speed cache in the camera.  This means that the camera can not record continuously at high speed, but rather will record at high speed until the cache is filled and then will have to wait while the processor and storage have a chance to process the data after the fact before it can do another high speed recording.
If you are able to use burst capture like this, it may be the best chance at getting something which is capable of both high speed capture at high quality and also not breaking the bank, but that only works if you are ok with the limitation of not being able to record continuously.

19085: <p>I'm interested in shooting <strong>slow-motion videos of sports</strong> (eg. ping-pong, badminton; for analysis and such). After trying an iPhone camera I wish to get something higher quality/more crisp (<strong>ideally 1080p@240fps</strong>).</p>
<p>However, finding something decent at an affordable price-tag seems to be rather difficult. <a href="http://www.hispeedcams.com" rel="nofollow noreferrer">hispeedcams.com</a> is a quite good source for this purpose. Here are some notable finds.</p>
<h1>research</h1>
<p>rather <strong>professional solutions</strong> (too expensive)</p>
<ul>
<li><a href="http://www.red.com/red-raven" rel="nofollow noreferrer">RED RAVEN</a> &quot;[...] 4.5K Full Format (FF) at up to 120 fps, or in <strong>2K FF at 240 fps</strong>, [...]&quot; (<a href="http://www.red.com/store/products/red-raven-brain-deposit?utm_source=red.com&amp;utm_medium=RRmicrosite&amp;utm_campaign=RED_RAVEN_Launch" rel="nofollow noreferrer">at $8,950.00 (USD), €9,030.00 (EUR), £7,970.00 (GBP)</a>)</li>
<li><a href="http://pro-av.panasonic.net/en/dvx4k/" rel="nofollow noreferrer">Panasonic AG-DVX200</a> &quot;<strong>120-fps Variable Frame Rate</strong>&quot; (<a href="https://rads.stackoverflow.com/amzn/click/com/B016043JWA" rel="nofollow noreferrer" rel="nofollow noreferrer">$3,795.00</a>)</li>
<li><a href="https://pro.sony.com/bbsc/ssr/product-NEXFS700UK/" rel="nofollow noreferrer">SONY NEX FS700</a> &quot;<strong>120fps at 4K</strong>&quot; (<a href="https://rads.stackoverflow.com/amzn/click/com/B00HWC8NCQ" rel="nofollow noreferrer" rel="nofollow noreferrer">$3,499.00</a>)</li>
</ul>
<p><strong>dedicated high speed cameras</strong> (more than needed)</p>
<ul>
<li><a href="https://edgertronic.com/our-cameras/sc1" rel="nofollow noreferrer">edgertronic SC1</a> &quot;- <strong>701 fps @ 720p</strong>: Color 8GB DDR3 Install IR Filter - 400-675nm response&quot; ($5,495.00)</li>
<li><a href="http://www.krontech.ca" rel="nofollow noreferrer">chronos 1.4</a> &quot;<strong>1,057fps [at] 1280x1024</strong>&quot; (<a href="http://www.krontech.ca/store.html#!/Cameras/c/21981408/offset=0&amp;sort=normal" rel="nofollow noreferrer">2,999.00$</a></li>
</ul>
<p><strong>action-cams</strong> (too limited): (&quot;<strong>240fps at 720p</strong> and <strong>120fps at</strong> [...] <strong>1080p</strong>&quot;)</p>
<ul>
<li><a href="http://www.hispeedcams.com/best-slow-motion-cameras-2016/" rel="nofollow noreferrer">Sony FDR-X3000</a> (<a href="https://rads.stackoverflow.com/amzn/click/com/B01LYSJB8A" rel="nofollow noreferrer" rel="nofollow noreferrer">$348.00</a>)</li>
<li><a href="http://www.hispeedcams.com/best-slow-motion-cameras-2016/" rel="nofollow noreferrer">GoPro Hero 5 Black</a> (<a href="https://rads.stackoverflow.com/amzn/click/com/B01M14ATO0" rel="nofollow noreferrer" rel="nofollow noreferrer">$399.00</a>)</li>
<li><a href="http://www.hispeedcams.com/yi-4k-slow-motion-samples/" rel="nofollow noreferrer">Yi 4k+</a> (<a href="https://rads.stackoverflow.com/amzn/click/com/B01CW4B2P8" rel="nofollow noreferrer" rel="nofollow noreferrer">$339.98</a>)</li>
</ul>
<p><strong>DSLM/MILC</strong> (which would also be nice as default photo cameras but don't have a optical TTL view finder)</p>
<ul>
<li><a href="http://www.panasonic.com/de/consumer/foto-video/lumix-g-wechselobjektivkameras/dc-gh5.html" rel="nofollow noreferrer">Panasonic GH5</a> apparently <strong>1080p@180fps</strong> (€ 1.999,00)</li>
<li><a href="https://www.sony.com/electronics/interchangeable-lens-cameras/ilce-6500-body-kit" rel="nofollow noreferrer">Sony A6500</a> <strong>1080p@120fps</strong> ($1,399.99)</li>
</ul>
<p>It would be nice to have something more versatile than action-cams, but less expensive than those professional devices. As I don't want to shoot slow-motion only, cameras specially designed for that aren't really what I am looking for either.</p>
<p>This leads to the (still quite expensive) GH5 (or similar DSLM) and also to a few</p>
<h1>questions:</h1>
<blockquote>
<p>What should I look for in gear for a beginner?</p>
<p>Is there something (DSLRs/DSLMs) in between (regarding price) GH5 and action-cams (similar to a6500) supporting slowmo ?</p>
</blockquote>
<p>Some specifications mention that high-speed capture is only available for a few seconds</p>
<blockquote>
<p>Is there always a maximum on how long can I capture slowmo if it is not noted?</p>
<p>If a camera is advertised with (eg.) 8sec 1000fps, at which rate could it record permanently then ?</p>
</blockquote>
<hr />
<h2>note:</h2>
<p><em>I have asked for DSLRs on <a href="https://photo.stackexchange.com/questions/89552/overview-of-camera-features-abilities?noredirect=1#comment159123_89552">photography</a> already with comments mentioning the GH5 only - I can remove this partial question if it is not fitting</em><br>
<em>I have split off the <a href="https://video.stackexchange.com/questions/21586/sdi-serial-digital-interface">SDI part-question here</a>.</em></p>
 14504: <p>You may want to look into Sony's camcorder line (even legacy; like the NX5U). </p>

<p>The NX5U and I think even the FX1000 (which is an HDV Tape Format and can be had used on a place like ebay for under $1000) could do bursts of full 1080p 240+ for a "limited time". </p>

<p>If I remember correctly the FX1000 by sony could do 240 frames at for 10 seconds. It would buffer the video into internal memory; then queue the tape; then record to tape when the 10 seconds was up. </p>

<p>It was limited in terms of it's usefulness; but it sounds like based of what you want to use the slow motion capture for; it may be worth looking into to. </p>

<p>Burst cameras (even the iPhone now does this); will give you a higher frame rate, with limited record time for a much lower price than say going the RED route or Phantom Route. </p>

<p>Or you could rent a RED, RED Epic's will do 480FPS at 1K; and they can be rented cheap; as they are everywhere... and sit on the shelf most day's of the week by people who own them. </p>
 2836: <p>There isn't really any magic bullet in high speed photography.  High speed photography is difficult because of the amount of data involved and the sensitivity necessary for the sensor.  Both of these factors combine to drive up the cost of all portions of the camera to do it well.  You can either sacrifice quality (which the iPhone does) or you can sacrifice affordability.</p>

<p>The higher the frame rate gets, the less time is available to expose each frame and thus the more sensitive it needs to be.  This makes the cost of the sensor higher.  Additionally, that data needs to be transferred off the sensor more quickly, which means more expensive sensor, it needs to be processed more quickly, which means more expensive electronics and it needs to be stored more quickly, which involves more expensive media.</p>

<p>Some cameras try to save on the cost and maximize quality by putting the money in to a faster sensor, but then putting a limited amount of high speed cache in the camera.  This means that the camera can not record continuously at high speed, but rather will record at high speed until the cache is filled and then will have to wait while the processor and storage have a chance to process the data after the fact before it can do another high speed recording.</p>

<p>If you are able to use burst capture like this, it may be the best chance at getting something which is capable of both high speed capture at high quality and also not breaking the bank, but that only works if you are ok with the limitation of not being able to record continuously.</p>
