Wednesday, May 14, 2014

The Science behind HDR photos


As usual, after the sadness of the whole “Results and Ranks”, comes the period where you really don't care about it anymore. This happens at least with me, and perhaps a good thing for me as well.

This time around, as I've mentioned it before, I took to Photography as a hobby. It took me a while to understand all the basics of photography and I became aware of some of the techniques used to enhance photos. This is going to be a HUGE post, so deal with it. Also, all the photos posted here were captured from my home, yesterday.

Single Photo HDR
Camera EOS 1000D  with GPlus HDR
The original photo straight from SLR
Quite boring, right?



I won't be going into the basics of photography due to the abundance of tutorials available on google, which perhaps will also offer a much better explanation of things. Exempli Gratia, I still don't know the difference in metering modes, although they “seem” to be very important. In this post, I will be talking about the effect which usually results in photos look more like CGI and less like actual images. This is the HDR or High Dynamic Range effect.

The camera (regardless if its a smart phone or bonkers expensive SLR) has a certain range of colors which they can express at a certain degree of exposure. Over exposed images have more detail in the poorly lighted parts of the photo, but a complete washout occurs in the bright part. Underexposure usually results in shadows in the dim lit parts but captures the bright part with much more detail. What HDR basically does is it merges these (usually 3, but can be more) differently exposed images into one single image. For eg, in a scattered cloudy landscape scene, it takes the sky part from the underexposed image, since it has more detail, and the scene part from the overexposed image, which has more detail for the dimly lit subjects, and combines them. This allows for much more range of colors to be present in a single photo, and since we can adjust the range of this “mixing” , we call it High Dynamic Range.

Normally exposed photo of my backyard (sort of)
Here, because of the excessive wind, 3 photo HDR didn't worked well. It resulted in too much ghosting. The app HDR was... well,decent...

Same photo, HDR with Google Plus app


There are softwares, like the Google Plus Photo app, which have inbuilt HDR filter which creates HDR image from a single photo, relying heavily on algorithms and codes. Of course, its good, but its not as good as the real deal, since you can never get the detail of 3 differently exposed photos from just one. Its like the software that converts 2D content into 3D, works, but not that good. However, in cases where the subjects move a lot, like trees swaying in the wind, the single shot HDR is the best way to go, as you would never be able to overlap the images, as explained by the previous set of photos.

Thankfully, nearly all the cameras and smart phones have the option of setting the exposure level, so you can take 3 photos with different exposure and combine them with software. Someone may say that their device has inbuilt HDR mode, especially inside the camera app itself. Well, yes! But, I think that the HDR mode in smart phones isn't that good... and if your device is a DSLR like the EOS 5D MK-III, then shame on you for reading all this, and I will conclude that you are an idiot having more money than you know what to do.

Normal Photo

HDR using Dynamic Photo HDR


What we need to do is that take three photos, in exactly the same position, with exposure -2, 0, and +2. These steps are called stops. So, we need 3 photos, each 2 stops apart. More than 3 also works, but the diff decreases exponentially. Once these photos are captured, copy them to a PC. Now, there are many softwares that can do the HDR effect. The obvious one is Photoshop. Photoshop CS4 and above have HDR command in Files>Automate>(somewhere). There is also one called Photomatix (Professionals only). But the one I use is called Dynamic Photo HDR, which has the advantage of being really easy to use and understand what you are doing and how will it affect the photo, along with the fact that its free! Also the fact that it works with JPEG, RAW, a single photo, and can mimic the HDR effect on videos, makes it perfect for me.

Once again, Photo a normal camera would capture.

Google Plus HDR

Dynamic photo HDR
Probably the best for this set.


The software itself is about 20 MB in size. After loading it, create a new file. Specify the 3 pictures you want to mix, then press the Guess EV button. After a while, you will see a preview of the HDR image. When you proceed, you will be asked to align the images, as the 3 photos will ALWAYS be a little bit different... Use the scrolls to adjust the images (Both sets). If the alignment is way off, use the anti-ghosting feature. (I recommend reading the inbuilt tutorial). When you are satisfied, hit next. After a while, it will say you to “Tone Map HDR”, proceed and start experimenting! Vary the intensity, the colors, the curves, the dynamic lighting, the radius and everything else till you are satisfied with the image. At the bottom right, there is the option to save. 

Standard Camera Click

Google Plus HDR

3 Photo Dynamic photo HDR
Once again the best IMO

HDR photography is a very exciting area. You should try it at least once. BUT, HDR effects work well only outdoors, and that too landscapes. The best HDR effects come where the sky is cloudy, and the sun peeks out. Indoor HDR photos, are very tough to master, but if done properly, can produce radical results. If you want more info on HDR images, the Instruction Manual of the Dynamic Photo HDR has more than enough content, which is super easy to understand, along with adequate theory and tips and tricks.

One more thing, you need brains to figure out if 1 pic HDR will be enough or 3 pictures would be required. Eg:- the first pic of the plane, I obviously cannot take 3 pictures! So single photo HDR, implying the App, would be better. If however the object does not moves, the 3 pic HDR is way ahead of the game.

Trying my 55-250 zoom lens
The TV Tower on the mountain is approx 25 km from my home


Be sure to check out my Google Plus profile for more examples of HDR images. Also, feel free to ask questions and show off your HDR pics to me! I may post some i like here... :)

Good day to all!