Thursday, August 14, 2008

Large strobe or is it?

For a portraitist, a large light source that throws dispersed light is heaven! When this kind of light falls on the skin of the subject, it brings out a soft skin texture which is attractive and soothing to view. Now, what if your light source is fairly large and it is controlled to be somewhat directional? You get a dramatic angled light. If drama is what you want, you've got it. My room has no other light except the light jumping off the LCD monitor of my computer. I asked the subject to stand in front of it and I positioned it lower than his eye level and tilt it slightly upwards. This was what I got: dramatic and soft.

Sunday, June 15, 2008

GPS for your camera

When the EXIF of your images are geotagged with actual (Latitude, Longitude, Altitude) coordinates, Google and other software can help locate the specific spot that the image was taken. You can display maps of the location you shot the images and click into it to see the images. How do you get that data into the EXIF?

Bascially, as of 2008, there are 2 ways:
  1. Real-time tagging
  2. Post-processing
Real-time tagging
For real-time tagging, the GPS data is passed into the camera and that data is received by the firmware of the camera. It's interpreted and encoded into the EXIF area of the image by the camera. This is probably the safest and most aligned with what Nikon had in mind when they provided the 10-pin socket for GPS device attachment. Within this solution, there are variations to achieve the same result.

You can get a regular GPS device spend a couple of hundred dollars more on specialized cables to connect that GPS to the camera. Examples of these cables can be found here.

Another way is to get a di-GPS and plug it directly onto your D200, D300 or D3 Nikon camera. It works well but the draining of electricity from the camera seemed a little high to me at 45 mAmp.

Yet another way is to carry a fairly affordable bluetooth-enabled GPS device in your pocket. Buy a Blue2Can and plug it into the camera. The Blue2Can will pick up the GPS data broadcast from your GPS in your pocket and convert it to data suitable for the camera 10-pin interface. No cables are involved. You do not need to turn your camera into a octopus with 8 cables crawling all over. And, the Blue2Can only use 2.5 mAmp of your camera battery.

I would trust real-time geotagging solution more than the next method because the raw geotagging data is presented to the camera and the writing of the data is completed by the firmware of the camera. This is safe.

There are several available methods out there. Most use a host of software to do it. But, the most popular method is to carry a GPS logger. Essentially, the GPS logger will write a timestamped GPS coordinate into its memory every so often (it is configurable from 1 sec to whatever). An image recorded in your camera also has a timestamp. When you upload all of your images into your computer at the end of the day, you need to run a piece of software which will go through all of your images' timestamps and match those of the GPS logger. This piece of software is often a free software (produced by unpaid software developer) which will then write the real GPS coordinates into your images' EXIF after it finds a matching timestamp in your image(s).

There some downside to this method.
  1. One obvious one is to get both the clock of the camera and the GPS logger in synched otherwise the matching step (described above) will not work correctly.
  2. Another downside is a little scary to me. I am essentially allowing a piece of software not approved nor tested by Nikon to write over certain parts of the images. I don't know about you but my out of town trips cost thousands of dollars and if there is any chance of anything corrupting my images, I would want to rule it all out --- totally! The cost of a GPS solution (even if it is $400 will only be a very small fraction of the cost of one trip). We really do not know how Nikon encodes their NEF files because it is a proprietary format and they do not have the need to tell you how and when they change and move certain bytes from here to there. These 3rd-party software may work fine now because the programmers have correctly guessed from reverse engineering where things are stored in each image.
Some of these software/devices are these:

One more variation is that of field post-processing geotagging. ATP Electronics came up with a solution where you stick your flash memory card into it after the images are taken and it will automatically write the geotags into your images right on the flash memory. This is great because you are post-processing it in the field. Hmmm, do I need to do post processing in the field? As of 2008, I do not think there is one for CF cards, they are so far for SD size cards only. Again, the 2 disadvantages mentioned above exists: something not produced by Nikon is writing over your images and I have to keep clocks in synched.

Once again, I am posting what I have researched onto this blog to help others with more readily available information. I do not claim to be a GPS expert and I certainly do not claim that you should rely on this blog for any critical tasks.

AcknowledgementsI gathered these information after I read many threads from forums in Photo.Net and

Tuesday, April 15, 2008

Robin's Hood

Many photographers who are puzzled over the hood issue get confounded even more when the world moved from film to the digital world. Do we really need a hood around the front end of a lens? Why can't an expensive lens take care of it without a hood? What's the reasoning behind it?

Let me start with a real life example and I assume that you do drive a car. Imagine yourself driving through a dark tunnel. When you are in the last 200-300 yards inside the tunnel, looking out from inside the tunnel, what do you see? You will notice that the scene outside the tunnel is crisp and almost sparkling clean. When you get closer to the edge of the tunnel, you notice that the crispness of the scene outside is reduced. When you finally approach the very exit of the tunnel, you will feel the crispness of the scene dropping by a large fraction compared to what you originally saw while you were deeper in the tunnel? Check it out next time when you drive through that tunnel!

That crisp image you saw while inside the tunnel is synonymous to what your film or digital sensor sees with the lens hood attached. Basically, the lateral light hitting the front element of the lens is blocked out by hood: a lot of it is blocked. When you are about to exit the tunnel, the lateral light begins to pour in from all directions, interfering with the relevant light from your subject that is entering your eyes (the lens). This effect lowers the contrast of the image cast on your retina and reduces the crispness of the edges of the subject you are looking at, too. This lateral light interference plagues film and digital sensors.

There's no lens I know of in the market that can reduce this effect without a hood. This is exactly the reason why you should get a hood even if the lens does not come with it. In general, it will give you a better image almost all of the time. Actually, right now, I cannot think of a situation it won't.

Happy hooding and don't take Robin's.