Camera Lens Depth of Field

I recently learned from Michael Willems that lens Depth of Field (DoF) is a law of physics. It depends on the aperture of the lens only. He taught me that it does not depend on the manufacturer, lens design or quality of the lens components or coatings.

A Canon 50mm F 1.8 will have the same DoF character as its Nikon sibling. A 50mm F 1.8 manufactured 50 years ago will have the same character as one today.

Other aspects of lens quality have advanced, for example aberrations, but DoF cannot.

I would like a choice – a fast lens that gathers lots of light so I can photograph the proverbial “black cat in a coal hole” but also one with good DoF so that its tail is in focus as well as its nose when the lens is fully open. But it can’t be done!

Unfortunately I do not have matched pairs of lenses to check this out for myself. I did have some fun taking some photos with my Canon EF 50mm F  2.5 “Compact Macro” at different apertures.

F 2.5

F 3.5

F 5.6

F 8

F 11

F 16

F 22

The F 2.5 is my fastest lens. I set up the Canon EOS-30D on a tripod, locked the mirror up and used a cable release. You can definitely see the increase in DoF as the aperture decreases. Beyond F 8 it does not get much better in practice as “diffraction effects” start to apply. I’m not sure if the diffraction effects are laws of physics too. It seems like we should be able to make improvements in that area using different formulae for optical glass that alter its diffraction capabilities.

By the way, there are some good tutorials on photography concepts at http://www.cambridgeincolour.com/tutorials.htm including one on DoF at http://www.cambridgeincolour.com/tutorials/depth-of-field.htm.

From the DoF tutorial the student can infer that the DoF is indeed a law of physics and not lens design because design is never mentioned.  There’s a theoretical DoF calculator where the brand or design of the lens isn’t a factor.

I ran a calculation using this tool with the following parameters:

• Camera type: DSLR with a crop factor of 1.6X.
• Actual lens focal length: 50mm.
• Focus distance to subject: 0.5 metres.

Then I varied the aperture and got the following results.

Aperture	Closest distance of acceptable sharpness (m)	Furthest distance of acceptable sharpness (m)	Total Depth of Field (m)
F 1.2	0.498	0.502	0.004
F 1.4	0.497	0.503	0.005
F 1.8	0.497	0.503	0.006
F 2	0.496	0.504	0.007
F 2.8	0.495	0.505	0.010
F 4	0.493	0.507	0.014
F 5.6	0.490	0.510	0.020
F 8	0.486	0.515	0.029
F 11	0.481	0.521	0.040
F 16	0.473	0.531	0.058
F 22	0.463	0.543	0.080

Note that if you use a full-frame 35mm sensor camera then the DoF is much greater. It varies from 0.007m at F 1.2 to 0.129m at F 22. Thus accurate focusing is more important on a crop camera.

I Need a New Camera!

At last I have a good reason to buy a new camera. The rubber cover on the side of my Canon EOS-30D has broken. It protects the two sockets for flash sync and cable release / remote control.

Actually, I should take the camera to Canon Thailand for a cleaning and adjustment. Their charges are reasonable. They’ll probably replace the cover for free.

500 Posts

This is the 500th post I have made to this blog since I started it on the 5th of June 2009.

It’s been fun. I enjoy writing. But I enjoy learning from people’s comments and questions even more.

So if you read something you like or that you disagree with – please leave me a comment.

Here’s to the next 500 posts.

Please note this post was written with no exclamation marks.

Nikon Camera GPS Patent Application

The Nikon Rumours web site collects information on patent applications Nikon has made. Here’s a recent post.

Searching patents is a good way to look at what companies are up to as they have to disclose quite a lot of information, albeit in legal jargon.

But patents are also about companies claiming technology territory and building a stock they can cross-license with others. And of course just because a company has a patent on something it does not mean they will make a product using it. Not soon, maybe not ever.

Having said that, Nikon filed an application recently for an integration of a GPS-enabled camera with digital maps. Here’s one of the images from the application:

The text of the patent is at the US Patent & Trademark Office site here. It’s application number is 20090268047.

I mention this one because it looks like Nikon is thinking the same way I was when I lamented here that my camera can show me where I am, but I am still lost. It’s some evidence that Nikon is continuing to invest in GPS enabled cameras. That’s good news.

Canon Picture Styles – Interesting Discussion

I meant to write a post in this blog about Canon’s Picture Styles, my limited understanding of them but how I relate them to my workflow. However, Michael Willems knows far more than I do so we are having an interesting discussion here.

So far I have learned more than I did by reading Canon’s online documentation here.

It’s a confusing subject and I made things worse for myself by trying to relate them to the adjustments I can make in Lightroom. Lightroom has to be a level playing field for all digital cameras so it does not handle them directly, but emulates them. And that’s where my brain starts to hurt!

If you are interested in learning more take a look at the discussion on Michael’s blog.

I thought Canon were going to invest more heavily in Picture Styles. For example they talked of releasing more on their web site for particular applications.

They released seven “extended function” styles in 2007 to augment the standard ones shipped with each camera and on Canon’s Digital Photo Professional (DPP) software. However nothing’s been released since.

I thought there would be an opportunity to extend the concept further. For example releasing styles that explicitly model traditional film types. I guess the development team were assigned to a different project after the Picture Style concept was embedded in all Canon DSLRs and in DPP.

Fear of Photoshop? Try Lightroom for Free – Gadgetwise Blog – NYTimes.com

Fear of Photoshop? Try Lightroom for Free – Gadgetwise Blog – NYTimes.com.

Yes – BUT IT’s a BETA! That means it is incomplete, is slower than Adobe want and may have loads of bugs that will destroy your work. The documentation is incomplete and there’s no support. Adobe released it so users can tell them what works and what doesn’t.

Adobe warn Beta Testers NOT to use it for production work. That means anything you care about.

Maybe Lightroom is a better tool for amateur photographers than the full version of Photoshop but I don’t think the NY Times should be encouraging users who aren’t experts to use the Beta.

I think Adobe has a free 30-day trial of the released 2.5 product. That’s been tested, has all the functionality advertised and is supported.

There are other issues that new Lightroom users need to understand. The biggest is its non-destructive editing. It works well, but you need to understand how Lightroom does it. For example, you must export the photos you edited. If you just pick up the files from the directory then you’ll be annoyed because you won’t see the changes you made in Lightroom.

Adobe also has Photoshop Elements which is easier to use than Lightroom. If people only want an editing tool Elements may be a better choice.

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I put that as a comment on the Gadgetwise blog entry. It will be interesting to see if the Moderator lets it through.

Night Shooting at Bangkok Hua Lamphong Station

It was pouring with rain when I got back to my local subway station Thailand Cultural Centre on Wednesday evening. Rather than getting soaked walking home I returned to the subway and took the next train to the end of the line: Hua Lamphong Station. I knew I could get to the station itself without getting wet. I have a monthly pass so it didn’t cost the Frugal Bangkok Photographer a satang.

I only had my Nikon Coolpix P6000 camera with me so I took a load of pictures on its “high ISO” setting – which meant it set the speed to 1600 ASA in the dark station.

There’s quite a lot of activity in the station in the evenings and many overnight trains depart between 8pm and 11pm for routes to the north and east.

Here’s a gallery of some of the photos I took. As expected they are extremely noisy. And I know that unattractive electronic noise does not equal attractive film grain. Still, the photos have a certain atmospheric appeal.

The white balance was way off in all the pictures because of the strange lighting. But Lightroom was good at correcting my JPEG pictures if I could find something that I knew was a neutral colour.

The main ticket hall.

The Train to Sikhoraphum

The Train to Sikhoraphum

The Train to Sikhoraphum

A SRT diesel shunter moves a train onto its platform ready for a late night departure.

A SRT diesel shunter moves a train onto its platform ready for a late night departure.

This DMU just arrived from Chachoengsao with the last commuter train of the day. Now it’s headed back to its depot for the night.

This DMU just arrived from Chachoengsao with the last commuter train of the day. Now it’s headed back to its depot for the night.

An Alstholm ALS diesel locomotive at the head of a recently arrived train at Hua Lamphong Station.

The Train to Sikhoraphum

The Train to Sikhoraphum

The main ticket hall.

You can click on a thumbnail to see a larger picture.

Finding the Make of a British Car

One of the most popular posts on this blog is DVLA Vehicle Enquiry. It’s second only to my non-informative post on the rumoured Nikon Coolpix P7000 camera.

In the DVLA Vehicle Enquiry post I comment that you need to know the vehicle’s make as well as its registration mark (license plate) to do a search. Well, I found a way around that due to a Flickr friend. (This is a reason people love Flickr – there are people on Flickr knowledgable about everything under the sun, including my nerdy interests.)

It came about because I saw a British registration plate on the back of a Daihatsu Hijet songtheaw (small bus with two rows of seats) in Bangkok. I posted the picture to Flickr with a comment that I’d like to find out what the plate was originally attached to.

How do I know L336VGK is a British registration? What can I say? I am a nerd of the first degree.

I got a couple of answers. One Flickr friend suggested I try the web site mycarcheck.com. Unfortunately it didn’t know anything about L336VGK.

Someone else suggested the venerable Royal Automobile Club (RAC). (The Queen calls them when her Bentley State Limousine breaks down).

Bentley State Limousine

The RAC has a service where you can find out the history of a vehicle. It’s intended to help people buying a used car. One “check” costs £14.99. That’s over 800 Baht! The Bangkok Frugal Photographer does not pay that kind of money for his nerdly inquiries: he doesn’t like to pay anything.

Fortunately my Flickr friend told me that you don’t need to pay to verify the vehicle’s make. They give that to you free to ensure you typed the registration correctly.

So here are the steps.

• Go to the RAC Web Site Car Check here.
• Select “Buy 1 Check – Just £14.99″. Don’t worry, you will not have to pay.
• That takes you to a RAC partner web site which shows a screen like this:

• You enter the registration number in the text box. It’s officially a Vehicle Registration Mark (VRM) and click “Check”.
• Then you some to this screen:

• You have to solve the two character captcha. That hinders an even greater nerd than me writing a program to perform the checks.
• Then you click the “Show” button, NOT the “Buy Now” button.
• If you have solved the captcha correctly you get a screen like this:

• There’s the vehicle’s make. L336VGK was originally on a Volkswagen Caravelle something like this:

• If you want to find out a bit more you can take the Make = Volkswagen, VRM = L336VGK to the DVLA Web Site and click on “Vehicle Enquiry” on the left toolbar.
• You enter the information thus:

• And you get this:

• So the vehicle is not currently licensed in the UK. I expect it was exported, perhaps to Thailand. They are both RHD countries. I have seen several cars with GB plates under their new Thai plates (as a mark of distinction I guess). In this case the VW’s owner may have given the old front plate (rear plates are black on yellow) to her friend the songtheaw driver.
• And 15 years later, a photo of it ends up on the internet. Isn’t the world amazing?

New Thai Tea

I was doing my weekly shopping at the local friendly Jusco supermarket yesterday. I put a box of my usual black tea into the trolley. An attractive young lady approached me and persuaded me to try a new brand: T-Max.

She had a small table set up to make sample cups for me to try. She impressed on me this tea is from Chiang Mai, Thailand.

The tea tasted the same to me as the Bangladesh brand I usually drink. I’m not a tea connoisseur – I take it with milk and sugar.

T-Max Black Tea

I like that their marketing department describe it as an “English Blend”. The English preference for tea is known worldwide. I think it means it is a strong-tasting tea.

As I bonus I got a free teacup with the purchase of a box of 50 tea bags. But in an “only in Thailand” glitch she said I didn’t get the cup if I bought a box of 100.

I didn’t have the presence of mind to ignore the “no photography” signs and snap a photo of the young lady with the tea. She seemed very grateful for my custom. Perhaps she gets a few satang for every box Jusco sells.

Most in-store promoters are too shy to approach a foreigner. I might talk to them in English. Oh no! Good that this lady was brave.

Labour costs are low in Thailand so most supermarkets have half a dozen promoters selling various products and any time. I don’t think that’s economic in North America or Europe except for major product introductions where customer education is important.

Small human moments like that are one of the many reasons I love living in Thailand. In America I recall supermarkets work it out so customers don’t need to interact with other humans at all. My local Safeway introduced expensive automated checkout scanners so customers can do it themselves. I don’t think that will happen here in my lifetime.

I like the personal touch.

The Back of the Box

No this is not me!

Singapore Picapps

Every so often I type something into Picapp to see what they have. The new pictures are not so interesting but again I found some old photos that I like.

I have spent a lot of time in Singapore so I like to see photos of the old city-state.