Tuesday, January 19, 2016

Lens Back Focus Test

Lens back focus has been a known issue for a long time.  With the arrival of 24mega pixels entry DSLRs, this issue become more prominent.

You can follow a simple test on your lens and camera to check for any auto focusing issue, below is simple video by a Malaysian young chap, but it is very to the point.

However, there is more to it.  From my own experience, I would like to add some points.

1. The focus chart that you use.  If you just download it from the internet, and print it out on normal print paper using your office laser printer, the print and paper qualities are not that high in the first place.  It is more difficult to tell which point is sharp, which point is not.

Sample Auto Focus Test Shot 1

The sample test shot above is an example.  Can you tell whether the word 'sharp' is sharp, or the numbers 2 & 4 below it are sharp?  Or the number 2 above it is sharp?

2. If you are doing this test with a zoom lens, you need to do it at the extreme ends of the zoom range, as well as the mid point.  You expect the performance to be consistent over the zoom range, but the actual fact is not.  You may have good auto focus at the mid point, but your auto focus may be off at the extreme ends.  You have to decide what is considered to be good for you.

That's all for today.  Happy shooting photos!

Friday, January 15, 2016

UberX vs Comfort Taxi

Uber had started its operation in Singapore for quite some time.  The review has been mixed, so I decided to give it a try and do my own comparison.

UberX is said to be the cheapest of the Uber series of services provided so it obviously became my No. 1 candidate for the comparison.

First, I hailed a Comfort taxi outside my office during lunch time, and went to a nearby sports complex.  We were not so lucky that day, as we hit multiple traffic lights, and waited the maximum wait time.  At the end, the trip cost me $6.50.

Then on another day, I got myself a UberX car, also during lunch time, from my office to the same sports complex.  The wait time for the car to come was 4 minutes.  The ride was smooth, and the driver took the exact same route as the Comfort taxi, but we were a bit more lucky this time, and didn't get stopped by traffic lights so often.  The trip cost me $6.80.

At first glance, we may conclude that UberX is more expensive than taxi, but then as you think about it, if you call a taxi, you need to pay additional ~$3.20, factoring in this cost, the total taxi fare would have been $6.50 + $3.20 = $9.70.  In this case, UberX is cheaper.

However, the not so good side of UberX is that you don't know how much your journey will cost before hand.  Their rate is based on real time demand.  If you are unlucky, you may end up with a much more expensive journey and it will really shock you.

Which one is better?  It is up to your own decision.  I probably will be more conservative and hail a cab, as I won't be surprised by a huge bill.