Originally Posted by
Jonathan Ashton
Roger I have been in touch with Martin Evening , Author, Adobe Photoshop CS6 for Photographers
here is his reply, I hope it may prove helpful, not having done mosaics I cannot add further.
Hi Jon,
Ideally, you want the individual images that you use to construct a mosaic or panorama stitch to all be of the same exposure brightness. That is, in an ideal world. When using Photomerge techniques in Photoshop if the exposure does not match you will see this at the align layers stage, but the blend layers function will correct for this. So, if you don't have perfect matches these can still be resolved in the processing.
To get a perfect match it is best to find a median exposure for your panorama and use this on a manual camera setting to shoot all the other shots. That way you are sure to have matching exposures. But, with most panoramas. the exposure required will vary across the scene, so you may end up shooting some photos too bright or too dark. You can get around this by combining HDR techniques with Photomerge, but that gets complicated. Therefore, if you need to expose differently for different sectors of the panorama and you aren't going to do HDR work, then maybe it is best to use an auto setting, have some photos appear brighter at the ACR processing stage and let Photoshop take care of the blending for you. These are the options you have at the moment as I see it. One thing that can help is to use the Match Exposures command in Lightroom to help even out exposure brightness differences in your selected photos.
I have processed lots of panoramas. Sometimes with uniform manual exposures, sometimes not, but always via Camera Raw or Lightroom first. Sounds to me like you don't need to change what you are doing that much.
Regards,
Martin