I have just upgraded my V4 installation to V5 and discovered that I now have problems with strange artefacts appearing in rendered outputs.

I am wondering if it because in V4 I could use wide Gamut and in V5 it is disabled or at least I cannot select it.

Basically I render the same sequence in V4 & V5. The V4 result is perfect and the V5 strange.

All clues much appreciated.

Wide gamut was deactivated by default for MP4 videos, because some users had compatibility issues for example with vimeo and with no 4 it doesn't really deliver any advantage.
You can turn it back on in the expert settings.
If you get artifacts, set the quality one step higher and try again.

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Enabling wide gamut did the trick. Thanks for the speedy reply.

Hello again. I am back to my rendering problem since the recent update to 5.2.2. 2 very similar sequences one fine and one not. The wide Gamut trick doesn't work anymore as the mp4 file which results is unrecognised by my imac. The Artefacts are strangely in a very dull bit of blue sky which has nothing going on. I tried a few different settings motion blur on and off and diff levels diff export from lightroom options. Different qualities and all to no success.
I read this thread https://forum.lrtimelapse.com/Thread-wei...ing-to-lr5 and tried forcing to 16:9 which solved the problem but it is a bit annoying to have to do as it limits my post prod camera movement. Is there anything else I can try?

Are you getting an orange warning in the render dialog? Which settings are you rendering with? Which player are you using for playback?
Please post a screenshot of your render dialog.

how do I post a picture?

aha figured it out ...

So yes orange warning but often get that and all is fine. playback is quicktime or Final Cut pro. Trying 3K instead of 4K right now .. no warning so lets see.. fingers crossed.

OK 3K success! so looks like I've just been a bit unlucky with something in this particular sequence compared with other similar ones.. .. .. good excuse to go pro! Thanks for the help.

With 4k 3:2 you are exceeding the MP4 specifications. That's why LRT gives the warning.
For such resolutions, ProRes is definitely the way to go. MP4 is a consumer codec.

I just went Pro .. super fast rendering and no strange artefacts ... Perfect. Thanks.