Here is an interesting montage that I have created for a book cover on feminine spirituality. The original sculpture is a large item in a stately home in England and I photographed it using the natural, available light coming into the gallery. I also tried to position myself not only to get a decent composition of the sculpture, but also to try and get a plain background - in this case a stone wall - instead of a background cluttered by other sculptures or windows.
Once I had downloaded it onto the computer, I then opened the image in Photoshop and used the rectangular marquee tool to draw a rectangle around the whole image. I then went into Edit/Copy. Then I went into File/New and the menu that opens then has the correct dimensions for a the new file canvas that I am going to create. At the bottom of this menu I selected the 'Clear background' option, opened the new file and then opened Edit/Paste to put this image of the sculpture onto a clear background. I then used the eraser tool to rub away all the backround, getting in very close with a small diameter eraser so that I could get into all the little corners and angles. I am then left with an image of the statue on a clear background. I then selected another image of a dramatic sky, making sure that the image of the sky was more than big enough to create a background to the sculpture image and that both files had the same resolution - in this case 72 d.p.i. These settings could be altered and matched using the Image/Image size menu. I chose the largest sky image that I could because if the image was quite small, even though I could enlarge it to a decent size, the image quality would be poor, looking 'grainy' or having a coarse texture.
I opened the sky image, and then, using the marqee tool, I drew a rectangle around the sculpture image, copied it as before and pasted it onto the sky image by clicking on the sky image window to activate it and then going into Edit/Paste. The sculture then sits against a dramatic sky. Using the 'Move' tool, I could move the sculture image around over the sky to get the best position. I wanted the lightning to appear to be related to the vase/beaker that she is holding aloft. Once I was happy with the positioning and also happy that there were no remanants of the original background wall in front of the sky, I cropped the image and then saved it as a jpeg by going into File/Save As and selecting jpeg as the file type.
In it's original form, this image is made up of two layers - the background sky (base layer) with a clear film (Layer 1) laid over it on which is printed the sculture image. However, once I save this as a jpeg, these layers are merged together and I will no longer have the opportunity to move the sculpture into a new position over the background. If I want to keep the option of being able to move the sculpture to a new position against the sky, I will also have to save the image as a Photoshop file rather than a jpeg.