You can use the Vision Color LUT plugin in VP14. It was free but now costs a little. It's slow, but then apparently so is the native Vegas LUT FX in VP15.

As monoparadox says, you can mimic a LUT with Vegas FX and improve the performance. Color Curves gives you more control than Levels. I did it for Panasonic V-Log footage and apparently got very close indeed, according to my scopes. If you're concerned that you're missing something by using FX instead of the LUT, you could switch back to using the "correct" LUT for final render.

As for the benefits of shooting log, it's a huge subject. It's worth reading that whole thread I linked to. My understanding is that the benefits are questionable if you're shooting 8-bit, but more worthwhile if you're shooting 10-bit or more. I don't shoot V-Log on my GH4 because I'm only shooting 8-bit internally. If I was recording 10-bit on an external recorder like an Atomos Shogun then I probably would.

thank you very much for your information.

as I'm a new guy on S-log. i heard this is more flexible on post production. but i'm not sure how does it work and how i can use this function on Vegas pro 14 regularly. i just know S-log, C-log, V-log is something which is similar to RAW-video but not RAW actually. i don't know how to release all the data in the file in post production.

I am new to S-log as well, I got curious since V15 has the native ofx plugin, so I downloaded some free stuff, last week-end I experimented a bit with my RX10iii in shooting S-Log2 compared similar shots with "normal", and did some reading on the subject. The Sony RX10iii seem to produce only 8 bit XAVC so according to Nick the benefits are questionable, on top of that the RX10iii switches to ISO 800 if you set it record in S-log, even if normally the scene would be ISO 100 auto metered. For me personally I will use S-log very sparsely, like when the subject is small and very brightly lit versus a large dark background.

S Log is a complex and probably the currently most misunderstood aspect of digital filmmaking. It does not really have anything to do with RAW, it's a way of vastly expanding your dynamic range by altering gamma curves, compression and using over exposure.
There's some great and demystifying tutorials by Alistair Chapman :

http://www.xdcam-user.com/2014/08/exposing-and-using-slog2-on-the-sony-a7s-part-one-gamma-and-exposure/

( s log etc starts at roughly 1 hour )

plenty more on YT

you could also do a quick'n dirty transcode to REC709 in sony catalyst browse, but i guess that would sort of defy the purpose of S-Log and all of its post possibilities.

If you have Vegas Pro 15 and a fast Computer, maybe you wish to use the new ACES 1.0 workflow to grade slog 2/3 to rec.709. But be Aware that grading of 8bit slog footage will have some limitations always, regardless if you use LUTs or an ACES workflow.

S-Log allows you to capture the widest dynamic range the camera is capable of; however, it can be problematic because it requires you to overexpose the footage anywhere from 1-2 stops over what Sony recommends, and it does not do well in low light. In my opinion, S-log 2 is better for daylight and uncontrollable light situations whereas S-log 3 is better for low light and controlled lighting situations. If you shoot s-log in low light, you are probably going to need to get the Neat Video plug-in to deal with noise in some parts of the shadows. As for grading, you can grade by hand or by using LUTS. If you are shooting 8-bit, it won't hold up to heavy grading, but can be modestly graded. If you don't upgrade to v15, then you will have to get the Vision Color plug-in as Nick suggested. You can also use Catalyst Browse, which is free, grade your footage, and export a 3D LUT, which you can then apply in Vegas. Personally, when grading by hand, I often find that a simple S-curve adjustment using Color Curves is all you need to punch some life back into the footage. I also like using Logarist, which is uses LUTS to get you in and out of the Logarist color space, which is not the same as ACES, but comparable. The best thing to do is to experiment with grading by hand, trying different LUTS, and just seeing what seems to bring the footage to life in a way that matches your vision. I like to say that once you understand the limitations of S-log, anything is possible. But, at least for me, it took me a while to get used to using it.

That's the exact misunderstanding I was talking about. Have a look at Alistair's tutorial, he really makes it clear what LOG is about and where it works and where it doesn't . It's NOT about high or low light situations, it's about being able to capture a scene that has an extremely wide dynamic range, like 14 stops from dark corners to a bright window for example, and where most other curves and filming techniques would fail by having to adapt to either the shadows or the highlights of the scene. When the S-log curves first became available on prosumer cams, there somehow was a widespread rumor that they were meant for low light situations, resulting in people all over the internet complaining about the amount of noise in their shadows.

"Normal" scenes are much better handled with non LOG picture profiles or curves, whereas some PPs are slightly better suited for low or high light situations due to how their curves handle shadows or highlights.

If you are shooting 8-bit, it won't hold up to heavy grading, but can be modestly graded.

I think that is one of the most important things to remember. Cameras like my a6300 can shoot S-Log internally but only 8-bit and that doesn't make much sense. It doesn't hold up in grading even after a LUT is applied. It does better when shoot in 4K (XAVC-S) transcoded to 1080p XAVC-I which is 10-bit. I would have to use an external recorder to get 10-bit 422 but that is not something I would want to carry around on my holiday trips. For most of my work, 8-bit with a standard picture profile works best as I can set the ISO to 100, compared to 800 for S-Log, and avoid most of the noise even in daylight.

"Normal" scenes are much better handled with non LOG picture profiles or curves

I fully agree.

For most of my work, 8-bit with a standard picture profile works best as I can set the ISO to 100, compared to 800 for S-Log, and avoid most of the noise even in daylight.

"Normal" scenes are much better handled with non LOG picture profiles or curves

I fully agree.

+1

That's also my experience with the Sony RX10 II using D-Range Optimizer : Auto

If people do not understand how to use slog they use it in lowlight situations and complain about noise.

Similar to people who are trained to shoot within the 6-7 stops of rec.709 only, ignoring that the cheapest processors can record about 10 stops today and ignoring that compressing 14 stops to 7 stops when grading that footage to rec. 709 will harm their 8bit footages dramatically. If such a grading should happen, then 8bit is not good enough.

But for the upcoming HDR future slog is a great approach, maybe also with 8bit as long no huge grading must be done.

The Film Convert plugin is great for S-Log 2. As well providing a simple S-Log 2 fix (once you download the preset for whatever Sony camera you use, like the RX100 IV I use myself), you can also adjust the curve slider for maximum dynamic range. And it’s great to have the different film presets. Normally I will choose whichever provides the best skin tones for the footage I’m working with. Plus, you get white balance and levels control in the same plugin. I never use its film grain though.

thank you very much for all your information.

actually, I'm not sure i need to take video of S-log or not. i took video mostly underwater (Diving). as the sun light will be absorbed by the water according to the depth. i can say most of the dive is in low light condition.

on the other hand, water will absorb the color when start going deep. red color loose the most in the video according to depth.

So "low light"'; "color balance"are the main issue in my footage.

i can see that the level of S-log is more flexible on post production. but the color balance seems not helpful on color loosing. e.g. if i just take a picture by RAW, it is very easy to adjust the color balance (recover the red color) in PS.

but i found it is very difficult on video, even i made it by S-log.

does S-log just benefit on brightness/levels??? but not that useful on color balance????

if i make most of the video on this condition, and color balance is not helpful, is it better for me to going back to normal instead of S-log, at least not much noise.

You might be better asking this question on the Wetpixel forum: http://wetpixel.com/forums/index.php?showforum=13

If you share any footage, or stills from your footage, I could show you how I would adjust the colours in Vegas using Color Curves etc..

Is the dynamic range in your footage so high that it is worthwhile to use slog? I would not assume so. In addition you have 8bit only If you have lowlight in addition, then foreget slog in that case.

I think in its current form, I wouldn't waste my time shooting SLOG and 'grading' in VP..even 15, as the only thing you can do is apply fixed LUTs or manually guess-drawing a log correction curve...The whole purpose of LOG is to capture wide dynamic range scenes and have options in post to optimize your individual scene to suit your needs. GAMMA and GAMUT are two different things, and for me and my little Sony A6300 8-bit XAVC-S jobbie, I found my happy land with Cine4 and a standard colour space, so all I have to do is crank up the contrast and fix the limits. This until Vegas can grade, or the Resolve roundtrip works again, or i have a 10Bit camera with HLG...