What version of Premiere? I'm running CC 2014 and just created 4K sequence and exported a JPEG and resulting image was 4K = 3840x2160. Any chance your Sequence might be 2K, even though the video content may be 4K? The Sequence is going to dictate the exported frame size. Select your Sequence, then "Sequence Settings" at top of screen to verify.
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I'm running Premier Elements 14.1
The properties window of my clip as read in the Project Assets window says Image Size: 3328 x 2496, Frame rate 29.97.
The Summary: Output shows 1920 x 1080 while the Source: shows 3840 x 2160.
See screen shot of the Export settings window.
And if I Select Frame instead of Custom it only shows four resolutions:
This is the Premiere Pro forum, not Elements, that is why things are different. Sorry, can't help you
The Forums page doesn't seem to have a forum for Premier Elements
This is why I posted my question here.
Where else can I submit my question with hopes of getting an answer?
Thank you John for pointing out where the forum is.
Thank you Desai for revealing how to get it to export at 4K size.
I suspect that they (those who set defaults and update features in the software) missed this part of the interface regarding 4K video. The "Frame" tab shows different ready to go resolutions, the highest of whcih is HD 1080 and on the custom screen, I wouldn't and I didn't think to unlock the ratio and then type in a higher resolution that displayed.