Wednesday, January 6, 2010

H.D.R and Panoramas


We have tried to make this post different from the regular tutorials on High Dynamic Range and Panoramas. In here we show you how to combine both the techniques first, and then take it one step further.
For the beginners, heres a quick overview of these techniques seperately.


High Dynamic Range, also popularly known as HDR is the tonal range of in the image. In simpler words, it is the transition range from the brightest part in an image to the darkest part. If the transition is in few steps, then the image has low dynamic range, and such an image would normally have blown highlights and high contrat. Simmilarly, if the transition has a lot of steps, lots of shades and colors with details in the brightest and the darkest part, then that image is said to have high dynamic range. The HDR technique is simply shooting two seperate exposures of the same frame by keeping the camera on tripod and just changing the shutter speed. Later in photoshop, you stack them in layers and paint out the dark and blown areas to give your image that HDR look.

Panoramas are images in a panoramic view, ie. that the width is atleast thrice the size of the height. You can take an image and crop it in that proportion to make a panorama out of it, but in doing so, the print size becomes too small. So, in comes the stitching technique. Here you take vertical frames one by one, while panning across the scene. Again, a tripod is a must for the perfect blending. Later in photoshop you blend them together with a automating tool called photomerge. If your shots are perfect, you can easily do it manually also. The resulting panorama will make for a good size print.

NOW, what we are doing in the next step, is combine these two techniques. Take a look at this chart below.


The above diagram should give you an idea of what we are trying to do. We are creating panoramas with high dynamic range. To do this, simply put, all you have to do is treat each frame of your panorama as an HDR image frame also, ie. when taking the first frame of the pano, shoot it in two different exposures. Repeat this for the other three or four frames you wish to take. In Photoshop or Elements, arrange the dark frames together and make one pano out of it. Do the same with the lighter shaded frames. Now, these two panoramas, stack them in layers in photoshop, and do the HDR painting to reveal shadow and highlight details. The resulting image of the above frames is shown below.



If you want more control, you can shoot three frames for HDR. Yes, that would be a third panorama to blend.....but no pain, no gain. Also, try to do little or absolutely no photoshop correction when making the first two (or three) panoramas. Do all the final corrections after blending the panos to an HDR image.

Another example of an HDR Pano:


The above image took a bit of more work because of the moving speed boat. In such cases, use that whole area where there is movement from the best exposed image. Ideally, this technique will work best only with landscapes with no movements or motion in it.

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