I read that for RAW images to be usable, they must be post-processed using a program like Photoshop or Lightroom.
If you shoot raw, can you preview the image on the LCD of your camera?
Is it turned into JPEG so it can be displayed, or you can you not see it until you post-process it outside the camera?
If it's the second answer (can't preview from camera) isn't it hard to determine whether you shot a good picture?
My question is how can you see from the digital screen of camera ,the preview of image in RAW format?
The camera creates interprets the RAW data into a viewable image for display purposes, so you can see it just fine on the camera's display. It also embeds a JPEG preview of the image in the RAW file, so that you have some way to tell which RAW file is which even before you process the RAW file into an image. When you import images into your computer you can generally see a little thumbnail image for each file, and that comes from the embedded preview image.
If it's the second(can't see prequel from camera) isn't hard to determine whether you shot a good picture?
It's often hard to know whether the image is really good because the display on the camera is much too small to see the entire image at full resolution, but you can usually see it well enough to know that the exposure is in the right ballpark, that the framing and composition are about what you wanted, etc. Most cameras will also let you look at histograms that show the distribution of pixels by brightness or color channel, which lets you determine the degree to which you may have under- or over-exposed some parts of the image.
If you shoot raw, can you preview the image on the LCD of your camera?
All digital photos start out as raw data.
If you are "shooting JPEG" the camera converts the raw data to a viewable image before storing it on the memory card. If you are "shooting raw" the camera saves the raw data to the memory card. But the camera also processes the raw data and creates a jpeg preview image and attaches it to the raw file. When you look at the picture on your camera's LCD screen that is almost always what you are viewing - the jpeg preview image.
You can't really view a RAW image, because a RAW file is not much of a viewable image. It is a set of linear monochrome luminance values that has not had gamma correction, other light curves, demosaicing, etc. applied. When the data is converted to RGB using demosaicing certain settings such as gamma, contrast, color balance and temperature, saturation, etc. are applied.
... isn't it hard to determine whether you shot a good picture?
Even when you look at the jpeg thumbnail/preview image on your camera's LCD it is often hard to tell if you shot a good picture. The screen is much lower resolution than your image. The brightness may be adjusted too bright or too dim. The color may not be accurate and is probably not adjusted to compensate for the ambient lighting where you are viewing it.
You are much better off learning to use the histogram (also drawn from the JPEG preview) to judge exposure rather than looking at the brightness of the LCD screen. A perfectly exposed image can look grossly overexposed if the LCD screen is at the brightest setting when you are in a darker environment. It can also look very dark when you are viewing it in very bright light.
The LCD display on the back of your camera is designed to make every picture you take look as good as it possibly can. In other words, it lies like a politician! If you are viewing a 25 MP image on a 1MP screen it means that each pixel on the screen is displaying a combined 5X5 pixel area of the original image. Your focus could be blurred by as much as the width of four pixels and you wouldn't be able to tell a difference from a perfectly sharp image! Likewise, the color and contrast are rendered in a way that the manufacturer thinks is most pleasing to the most potential buyers. If the preview picture on the LCD screen reduced contrast enough to display the entire dynamic range of the RAW file, no one who buys a camera based on how the picture they just took in the crappy light of the store looks on the back of the screen would ever leave the store with one.
