All photos NOT taken with my iphone have vanished from iphoto

Question

I have just found that all pictures in iphoto except those taken with my iPhone have simply gone. I have searched for them but they don't appear to be anywhere on the machine. Furthermore, I have two cameras that I have downloaded images from quite happily for years from and now my Macbook can't download from them. It doesn't recognise one and just says there's a fault and it can't download images from the other.
Can anyone help? 

Answer 1

The preceding reply is only accurate in part.
You, too, can influence the way your photos look in an email message read on your friend's computer. You do not say how you enclose the photos as attachments, so I hope you are using the email button at the bottom of the iPhoto window (after having selected the one or more photos you wish to send). Clicking the email button should bring up a dialogue window, asking you to select the Size of enclosure you wish to send: using the drop-down menu, you can select between Small, Medium, Large, and Actual size. The size you select will depend on the eventual use that is to be made of the photos: if this is simply for viewing in the email message, then Small and Medium are appropriate; if the photos are to be viewed more closely, or printed at a relatively small size, then Large might be a better choice; if the photos are to be further processed, or printed in rather better quality, then Actual size is what is needed (actually, you might then simply prefer to send the originals).
The other selection boxes in the dialogue window are to allow you to include textual information, embedded in the photo file(s). Such information should already have been entered in the Information panel in iPhoto for each photo. Usually, you can leave these selection boxes unchecked.