Posts tagged Photography

NiZn PowerGenix Batteries

I’ve been meaning to write about a set of interesting new rechargeable AA batteries I came across for a while now. Last year (wow, has it really been that long?) I came across a review on engadget of some PowerGenix NiZn (Nickel Zinc) rechargeable batteries which promised better performance, higher voltage than NiMH, and greater capacity. I was compelled to invest in some otherwise experimental and new rechargeables for a few reasons:

Doing indoor photography with my girlfriend – especially weddings – it becomes apparent just how many AAs you can go through quickly. So many that it’s relatively expensive and prohibitive to keep up and carry all those batteries around. They’re expensive, and just don’t last long enough. One or two hundred shots or so, if I recall correctly.

SB600 Flash

Anyhow, right after getting them and charging them, I decided to shoot a wedding with my SB600 flash and the NiZn batteries. I was immediately floored at how fast the flash recharged and how performance never seemed to fade like alkalines do. Usually, flash performance seems to fall off exponentially with the generic alkaline batteries – eventually the time it takes to recharge gets so long you can’t take photos of anything. So what’s useful about the NiZn was the hugely fast, super quick recharge time.

That’s also… the problem. While shooting that wedding, I managed to somehow completely blow out the flash. This thing was under 2 months old, used at a few other weddings, without what I’d consider very many activations at all. The SB600 apparently has no thermal cutoff at all, allowing the whole thing to overheat. Whatever the case, while shotgunning some photos of the dance floor in low light, it stopped working. The flash didn’t feel notably hot, but the flash showed an error on the screen and wouldn’t work from then on. Anyhow, I shipped the flash back into Nikon and had a replacement about a month later, but the point is that I’m now far too scared to repeat the “experiment” again.

It seems that two things are possible:

  • The SB600 lacks adequate/any thermal protection preventing the flash from overheating or being fired too quickly
  • The SB600 possibly relies on alkaline AA battery performance to prevent the flash from being overheated
    • I realize that the NiZn PowerGenix batteries are 1.6 volts (as opposed to the 1.5 standard for alkaline, and 1.2 for NiMH). At the same time, there should definitely be regulation of some kind preventing failure.

The batteries themselves are remarkable in their performance, but it’s that which scares me out of using them in the flash where they’re needed most.

NiZn PowerGenix AA Batteries

What brings this all up is that engadget compared the PowerGenix batteries to some of the other new (and exotic) choices from Energizer and Sanyo Eneloop, and I left a comment.

I purchased the NiZn batteries after your initial review and was super stoked when they came. I’m an avid digital photographer, and replacing flash batteries at a wedding actually gets expensive enough to make buying a bunch of rechargables worthwhile.

That said, I had a brand new SB600 (just like yours) burn out with no warning while shooting with the NiZn batteries. I had to ship the whole thing in and get it replaced. I browsed the Fred Miranda forums some time later and found a bunch of people with the same issue – the SB600 relies on Alkaline batteries simply not being able to drive enough power quick enough when shotgunning that flash to avoid burning out. There isn’t any thermal safeguard.

So be warned, even though you’re testing on an SB600, if you actually do go out and abuse the batteries like you would at a big event firing the flash a lot, you WILL nuke your stuff. I’m too scared to use my NiZn batteries now.

That Fred Miranda forum thread I mentioned is here.

Photosynthing everything

These past couple of days, I’ve finally gotten some time to work on the tremendous backlog of photos that I have sitting around from a number of trips. Among those pictures are sets of photos in the hundreds destined for photosynth. A number of my friends have expressed interest in what the software is, what it does, how it works, and how to take photos best suited for processing. I think now is a great opportunity to go over the basics.

What Photosynth Does

First of all, what Photosynth does is create a 3D point cloud model/representation of an object or scene from a set of photos. Depending on the scene complexity, the number of photos might be in the tens, or hundreds for sufficiently complicated scenes. It all depends on the model and how much time you have on your hands.

Perhaps the best way to explain it, is to see it. The following is a synth of the Pantheon that I recently finished processing, constructed from photos taken by my brother and I from a D80 and D90:

How it does it

The software uses feature extraction to identify textures in parts of each image that are similar, then tries to fit each corresponding from each image together to create a perspective-correct view. The process is extremely computationally intensive, but only needs to be done on the initial set of images to determine position and location. The beauty, of course, is that this process requires no human input for reconstructing the scene; it’s entirely computationally derived.

I won’t claim to be the most qualified to talk about it, but it does use feature extraction and some fancy fitting to work. An important note is that the software works based on unique features in texture, not necessarily on structure. This is why synths with lots of unique patterns turn out extremely well, while others don’t.

Creation

Creating the actual Synth is actually the easiest step; just create an account, install the software, add your photos, and go.

The real work in that process is creating proper tags, descriptions, and then adding geotagging data from photos, or later on in the web interface. Doing so is a great way to get your synth recognized.

How to take the best shots

There’s a great how-to on the official Photosynth website that goes over how to take pictures optimally, but I’d like to share some of my own.

If I’m taking a photo of a single object, something like this column, for example, I’ll try to stay equal distance away from the object, and take photos in steady progression around the subject.

The important thing to keep in mind is that although Photosynth can extrapolate the point cloud from features, it still cannot extrapolate images that you haven’t given it. Simply put, if you want to get the nice scrubber bar to circle around an object, you’ll need to take the requisite photos to make it. I find that pacing steadily around while taking photos at regular intervals is the best way.

  1. Take photos of subjects from a variety of angles. If you can, from every angle possible in an equal manner.
  2. Take photos from a single perspective pointing in multiple directions. I find that spinning around taking photos from each corner of the room works marvelously well; even though you look slightly special in the process.
  3. The most important thing to keep in mind is that quantity is generally on your side; so long as there is variety in the shots, but overlap as well.
  4. Choose subjects that have a variety of textures and features. Things like the Sistine Chapel synth really well because unique texture is everywhere, while cars generally don’t because of their solid color.
  5. Take wide angle shots of the entire room from the four corners first, then one from the center. Afterwards, take photos of objects/features close up. These are things that people will want to focus on when viewing later; a good example are pictures on the wall in a museum or specific fresco sections on a large wall.

Shameless plug

Some of my favorite Photosynth creations are:

  • Piazza San Marco: Link
  • Sistine Chapel: Link
  • Artemision Bronze: Link
  • Salpointe Graduation 2009: Link
  • Replica of Equestrian Statue of Marcus Aurelius: Link
  • Library of Celsus: Link
  • Pantheon: Link

For equal comparison, here are some that didn’t turn out so well:

  • Parthenon: Link
  • Olympic Grounds: Link
  • Port of Dubrovnik: Link