Long discussion about a simple thingy.

1. Pixel is a dimensionless term. There is no specification how big a pixel is. How big it SHOWS is depending on the used hardware, printer, monitor, scanner, camera, etc. For example with a inkjet-printer a pixel can be seen as one dot coming from the spray valve..

2. According to that pixel definition a image consists of its size, e.g. paper 11 * 8,5 inch, AND the resolution what the technical equippement can/shall print, show, scan etc. And this resolution is normally named in DPI = Dot per Inch, sometimes olderwise I have found also PPI = Pixel per Inch. DPI is normally convienient on paper where PPI was used for monitors ... in the times there you could count them directly on the screen without magnifying glas :-) So in this case igohigh wanted a papersize of 11 * 8,5 inch with a resolution of 300 DPI. Poser did that correctly I guess. But Photoshop has by default a other interpretation and shows as 72 DPI in size 45.828x35.412 inches. If you divide 300 through 72 you get a factor 4.16666. Now multiplicate the 11 or 8.5 inch with that factor and you get relatively exact the sizes 45,8... or 35.4,,, So nothing has changed to the pixel content of the file and caisson is absolutely right with his hint to change the DPI in Photoshop with out resampling the stuff.

Every time output size, e.g. a paper sheet, and resolution go hand in hand and determine how much pixels come into the file, on paper, on monitor or for example on a film. For example old diapositive films had DPI of 2500 and more depending on the graininess of the emulsion. Photoshop and also TGA use that low DPI count as a relict of times there monitor could not handle more.

@Rhia474 if that is a new Poser bug (I don't believe) can only be said if your given output size in inches stayed the same. You have only named the DPI but not the image size.