Wednesday, June 11, 2008

What is HDR?

Now I'm sure you all have seen those awesome photos with vibrant clouds which still retain enough detail so that everthing else doesn't look like a silhouette. If you haven't then you haven't been keeping your eyes open. On with the show!

What is HDR?

HDR stands for High Dynamic Range. I'm not going to go into the technicalities as other places explain this better. Like here or here. This site is for simple advice and quick "how-to" advice. The basic jist of the process is this: when you take a photo on your camera, your sensor can only grab so much information. If your photo is bright, then it captures lots of "bright" data, limiting how much "dark" data (such as shadows, dark corners etc) it captures. This is most evident in something like a sunset shot. If you have trees or anything else in the same composition and it receives minimal light, it will just look like a silhouette.

Now the opposite is also true. Let's say you're taking a photo of a face outside, on a bright sunny day. If you look at the face, you'll see all the colour gradients and detail, but have a look at the sky in the background. It'll be very close to white with very little detail in the clouds at all. (Yes, at some point, I will take photos to illustrate these principles - use your imagination for now).

These typical images are called LDR (low dynamic range) images as they can only capture one specific "range" of values. What HDR is simply taking 2 or more LDRs at different exposures to create something that has the widest dynamic range.

What do I mean? Let's take the face example. If you are taking a photo of a face and you set your exposure so that the face is correctly exposed, then chances are the clouds will be over exposed and you'll lose detail. Now if you correctly expose for clouds, your face will look to dark and again you lose detail. But if you take both shots and magically combine them, you keep all that detail. Sweet and simple huh? Only if you have the right software- combining manually is just painful!

This is why software like Photomatix and the new feature Photoshop CS3 has a HDR function. It allows you to select an image at different exposures and combine them into one image. In my opinion, Photomatix works far better.

Friday, February 1, 2008

batch processing and resizing images using photoshop

This is a quick tutorial from yours truly so that you can batch process/resize images quickly. Using this, you an just let photoshop do everything in the background and spend your time on more worthwhile endeavours. Like juggling pancakes.

Ok, first up, I'm using Photoshop CS3. Other versions have minor quirk changes, which I'm sure anyone with half a brain can figure out. If you truly have problems, leave a comment and I'll try to get back to you.

[ Step one ]

Put all the images that you want to batch process into one folder. For the sake of this tutorial, I'll assume what you all want to do is resize big, high resolution images into lower resolution/low file size images.

[ Step two ]

Go to Photoshop, hit File>Scripts>Image Processor

[ Step three ]

For the "select images to process", select the folder

[ Step four ]

Now for the "select location to save..." part, either select "use same folder" and Photoshop will resize/lower the resolution and overwrite the file, or you can specify a new directory to actually save it into if you want to preserve the originals. All this should be "well, duh!" -ish.

[ Step five ]

Select what you want the output to be: JPG, TIFF or PSD. Then select what quality of file you want (for JPGs) and what size you want them to be in pixels. Hit "Run" and watch Photoshop do its thang. So go on, get juggling! You have no excuse anymore!