Sunday, December 1, 2013

Canon EF 24-70mm f/2.8L II USM Lens Test

After I bought a Canon EF 24-70mm f/2.8L II USM lens for my wife's camera and doing a quick test, I was initially surprised by how terrible autofocus was. Every forum, review, and blog post I've read stated the lens was suppose to be super-sharp. It wasn't the case for me initially. Pictures I took of people were never sharp, especially at 70mm f/2.8.

After a bit of time playing around with the lens, I finally figured out why. It boiled down to several issues:

1. I wasn't use to the extremely shallow depth of field, which means that at 70mm, if I took a picture of a person with the focus centered on the tip of the nose, their nose would be in focus, but their face would end up blurry. I had to shift the focus point to between the eyes.

2. AF Microadjustment -- the results, albeit trivial, do make a difference between parts of the subject having a "soft" focus vs having a super-sharp focus throughout. This made the most difference at 24mm and negligible difference at 70mm. I recommend following the tethered approach described in Ophyrs Photography site. I've tried all of the approaches with the tethered approach giving the most accurate results.

Finally, to highlight the subtle change between before and after AF microadjustment, here are photos taken of the same subject with the focal point on the nose of the bear. The pictures were taken at f/2.8 with a 24mm focal length. Left is before AF microadjustment, right is after. The difference is subtle, but the fur in the lower left below the nose is somewhat sharper in the right image.

And for a different target that's more noticeable:

And a quick test showing off what this lens can do:

Friday, August 16, 2013

Chromecast on the Open-sourced Asus RT-N65U firmware

After 3 hours of fiddling around with settings, I finally got my Chromecast up and running. Video played from Chrome websites runs smoothly.  The setup was a bit frustrating, but once all of that's taken care and out of the way, things are smooth from then on. I just wished there had been a bit more information provided about network router settings or an explanation of what the setup process involved so that I could figure out what settings I needed enabled.

There are several things that you need to be mindful of:

1. The Chromecast stick needs to be able to send UPnP packets to whatever device you are using to configure ChromeCast. If you have a software firewall policy on your computer, you'll need to make sure that it accepts incoming connections for the ChromeCast app -OR- for UDP ports 32768 - 61000. On my MacBook pro, I had "block all incoming connections" enabled by default. You'll need to disable this, or make an exception to the relevant UDP ports. If you don't have admin rights on your computer, a work around is to use your phone or tablet where there isn't a firewall setting by default. 

2. If you have dual wifi mode enabled (i.e., 2.4GHz wifi and 5GHz wifi), you'll need to disable the 5GHz wifi.  Make sure UPnP packet routing is enabled.  NOTE: You do NOT need to allow UPnP packets through your router's firewall. Allowing incoming UPnP packets from the outside world into your LAN is a bit dangerous.  You only need to make sure that UPnP packets can be routed internally on your LAN. 

3. Make sure AP Isolation is disabled. On my router, this is two settings. "Set AP Isolated" and "Isolation between Main and Guest AP". Both have to be disabled.

4. Finally, if you're still struggling with getting ChromeCast to connect:
  - Turn on IGMP Snooping.
  - Disable WMM and also disable Packet Aggregation temporarily.
  - If you can, set the multicast rate to HTMIX (1S) 30 MBps

I'm using the rt-n65u firmware hosted here ( ) and had to make the following changes:

Under Advanced Settings --> Wireless 5GHz:
  - Enable Radio = OFF

Under Advanced Settings --> Wireless 2.4GHz:
  - Goto Professional tab:
  - AP Isolated = OFF
  - Isolation between Main and Guest AP = OFF
  - Enable IGMP Snooping? = ON
  - Multicast Rate (Mbps) = HTMIX (1S) 30 Mbps
  (optionally, you can change this back later):
   - Enable Packet Aggregation = Disable
   - Enable WMM? = Disable

Under Advanced Settings --> LAN --> IPTV:
   - Enable multicast routing = ON
   - TTL correction for multicast packets = NO
   - IPTV UDP Multicast to HTTP Proxy Port = 0   [disabled]
   - eXtensible UPnP agent (xupnpd), Web port = 0 [disabled]
   Multicast traffic - WiFi 2.4 Ghz
   - Enable IGMP Snooping = ON
   - Multicast Rate (Mbps) = HTMIX (1S) 30Mbps

Under Advanced Settings --> WAN
   - Enable IGD UPnP = NO   [You'll never want to allow WAN UPnP packets in] 

[Edit: 2014.02.02]:
Following the advice of one of the comments, try turning off IGMP snooping after setting up Chromecast. It seems to have resolved issues with dropped casting connections. Also, try enabling WMM as well. I'm testing this pre-Superbowl (

Friday, August 9, 2013

LinkedIn ?

It seems like everyone in the Silicon Valley area uses LinkedIn. I remember signing up for an account when they first started out. As a joke, I wrote that my profession was a farmer and that I loved milking cows. Then, over the years, friends added me. People I met added me. And then, one year, I forgot my password.  I learned after my interview at my current job that LinkedIn is actually quite popular and a place that employer's use to search for employees. (Side-note: my current employer doesn't actually use LinkedIn. They require someone at the company to have personal knowledge of you and refer you. But they do look at your LinkedIn profile if it's provided.)

Shortly after joining my current employer, I removed my joke "farmer" profession, but I haven't really updated my profile to include any technical expertise or information about myself. To me, LinkedIn seems like the perfect place to gather intelligence and profile someone you want to hack. I once worked for a government intelligence agency -- so, I've heard all the scary stories.

I've re-considered the benefits of LinkedIn and decided to throw in the towel. I've yet to add additional details to my LinkedIn profile. It seems like doing so would be beneficial to all of the folks who know me. I can offer feedback about their work experience, etc.

Just my thoughts.. have anyone of you used LinkedIn ? Any interesting stories to share?

Sunday, June 9, 2013

Cast-Iron cookware -- the lazy man's cookware

My wife and I have a deal going on -- if she cooks, then I wash the dishes. If I cook, then she washes the dishes. Both of us hate washing dishes, especially the frying pan which absolutely cannot go in the dishwasher (we tried it once but destroyed a non-stick frying pan in the process).

Recently, we switched to a cast-iron frying pan after our white ceramic frying pan turned brown and lost its non-stick functionality. It was a $25 investment that lasted for 6 months. We thought about switching to cast-iron after hearing from friends about not needing to wash such cookware after cooking. Oh man, what a dream come true!

Above is a picture of our cast-iron -- a Lodge Logic 10" Skillet (here). It costed $16 when we bought it. The blue rubber handles are separate accessories that we purchased to avoid burning our hands when touching the handles. The main appeal of using cast iron is that after cooking, you don't need to wash it.  Okay, you should probably rinse off/towel off any food bits if you want to avoid cockroaches, but otherwise, you want whatever oils from what you last cooked to dry onto the surface. We found it easy to rinse the skillet in hot water just after cooking. Then towel it dry and dab a bit of oil onto the surface. Note: If you wash the skillet with soap, the coating of oil will come off and you'll have to re-season the skillet which takes at least an hour.

After a week of cooking, we found the food that we've cooked getting tastier and tastier.  The taste of each cooking has gotten richer as each previous cooking's flavor soaks into the skillet. Also, the skillet becomes more and more non-stick over time as the oil coating thickens. The only downsides that we experienced with the skillet are:

  1. It's heavy as hell to lift. My wife finds it impossible to lift.
  2. There's a lot more smoke when cooking. The skillet gets hot and stays hot for a longer period of time. Don't fry with olive oil or oil the skillet with olive oil. Olive oil has a low-smoke point and isn't healthy when it breaks down at temperatures above the smoke point.  Use grapeseed oil or oils with higher smoke-point temperatures.
  3. You'll need to buy a good pair of oven mitts or purchase rubber handles for the skillet.
  4. You'll need to tell over-zealous family members NOT to wash your greasy skillet if they attempt to help you clean your kitchen (has not happened to us yet :-)).
I'm looking forward to cooking with the cast-iron tomorrow. It's a lot more fun to cook now that I don't have to clean as much.

Saturday, June 8, 2013

Learning Vimscript

One thing that I find myself doing a lot of on my spare time is trying to improve my efficiency when coding. At work, my editor of choice is vim. A lot of people use eclipse, but I like vim because of it's customizability and simplicity.

Anyway, I found a good site that covers some of the basics in vimscript. See

Happy Vim-ing :)