No, you cannot do that. The whole idea behind working in Lightroom is that the original images, the ones downloaded from the camera, are left completely untouched. If you don't want to go from Lightroom to Photoshop with your JPEG images then you will have to work with them from Bridge. The few times that I have shot JPEG images, I just go ahead and process them through Lightroom like I do my raw images. I end up with a TIF image alongside each JPEG for the ones that I resort to Photoshop.
Ok thanks. But it's difficult to keep thinks straight when you have more than one camera and more than one photographer and more than one file method right?
Say one guy shoots Raw out of a 5D and another guy shoots Jpeg out of a Rebel XT? Your edit settings in the preferences can't exceed what a file spec is capable of right? So I could open the 5d Raw 16bc/Tiff/ProPhoto/240ppi no problem. But if I use those settings with a jpeg whose original settings are sRGB 72ppi... maybe that's what the smart object feature is for?
If you're talking about default settings, they are file type-specific.
Once the JPGs are being adjusted in LR, they are using the LR internal 16-bit ProPhoto-based colorspace so why wouldn’t you also want to use 16-bit ProPhoto for them? Is LR only a file-browser or are you using it to make initial adjustments before opening into PS.
Another question would be if your LR and PS/ACR versions are matched (for example LR 5.6, PS-CC/ACR 8.6) or if your PS version is older so you have to create a TIF on the way to PS instead of just letting PS call ACR to open everything from LR?
The way things work using Edit In from LR if the versions are matched would be that PS receives the LR adjustments, then calls ACR to open the file with those LR adjustments and ACR is in fact reading the original JPG and applying the adjustments before opening it into PS. Once in PS you’re using whatever workspace you have defined for RGB and hopefully in 16-bit to avoid posterization.