In Focus, Bangkok Photography Blog September 13th, 2008

Focal Length, Southern Thailand

Vietnam Hotel Guide
• Celadon Hotel
• Duy Tan Hotel
• Festival Hue Hotel
• Heritage Hotel Hue

Feature Photograph

This week we’re going to have “feature photographs” instead of just one main image. I was fortunate enough to be invited to photograph a performance at the Thailand Cultural Center as a Requiem in Memory of the Princess Galyani Vadhana. I was one of only 3-4 photographers at the event, and the only farang photographer.

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The orchestra and choir led by Phukom Srinarong and Pawasut Piriyapongrat (conductors) were superb! This is a solemn event in remembrance of the Princess and everyone was dressed appropriately for the occasion, very respectful, and mindful of the correct decorum and manners. Because this was such a special event I decided to run a small sample from the performance to share with the readers.

I set up all the way in the rear and mostly used a 300mm F2.8 lens on a very sturdy tripod. The light temperature used for such halls is tungsten or about 2800 degrees Kelvin. At this distance it takes a really high end lens to reach the distance, allow enough light in a dim hall, and still resolve enough detail to provide a high quality image. At 300mm there can be absolutely no shaking or vibration on the tripod so proper technique including the use of a remote shutter release is mandatory.

This kind of performance doesn’t have many different scenes as everyone stays in the same position and mostly moves their arms and hands to perform. It’s easy to end up with hundreds of shots that all look alike, so it’s good to try to isolate different parts of the orchestra and choir so you have some variety.

It’s also important to capture the few parts of the performance where individuals are receiving awards and notice. I really enjoyed myself and look forward to being invited back in the future.

Weekly Photo Outing

This week I’m going to share one of my many trips to Thailand’s troubled southern regions of Pattani, Yala, and Naratihwat. You’ve probably read about these provinces in the Bangkok Post and other papers and know there have been more than a few bombings, beheadings, shootings, and other forms of violence. I’ve taken more than a few trips to these regions to investigate and photograph the ongoing conflict, but this time I’m going to share something I consider much more enjoyable, my visit to the Kris Master who hand makes beautiful traditional kris daggers by advanced order, and regularly makes one off pieces for HM the King and visiting/honored heads of state.

During the time of my visit the bombings and violence were at their normal levels so my contact in the Thai SF community set me up with an armed military escort of roughly 23 men. We convoyed to the kris masters home where he greeted us with smiles and his entire family were there to greet us as well, meanwhile the soldiers secured the perimeter and advised me that they wouldn’t recommend staying past a certain period of time in case anyone decided to organize a neighborhood welcoming committee.

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Once we made the introductions we got right down to business and they showed me how they made these beautiful works of art using hand tools, a homemade forge, and an array of home built tools and jigs. He also showed us the steel he mixed during the forging and hand hammering which included certain types of metal chain, boat anchors, railroad track, leaf springs, and other items selected for their specific content of iron, steel, nickel, zinc, and other metals. It really was amazing to learn and see how they made such handsome weapons from what appeared to be discarded and rusty scrap.

After we’d seen his outdoor shop, forge, and work area he went into his home and came out with a armload of sample kris’s. Laying them out on a table I took my time and admired each individual piece, each one having a unique and distinctive pattern running through the blade brought on through the design of that one blade. To decide how he would build the blade he would ask the customer specific questions ranging from the spiritual to military experience and then in what he described a spiritual process spend the next 3-8 weeks fashioning just that one blade! These are not hastily made, the average kris takes at least three and a half weeks, some take that many months. They work on it as they have spiritual inspiration, and then work on another one, and then will come back to it again when they feel it’s the right time. He estimated that roughly 120-500 man hours goes into each kris.

The drive down south is interesting, and once you reach Pattani and head south into Yala you’ll notice fewer (much) temples and more mosques, more Muslim clothing, hair styles, and other traditional Muslim garb, foods, and events. Despite the ever present threat of violence and being targeted simply for being a foreigner I very much enjoyed my time in the south on this particular trip. I DO NOT RECOMMEND this area for the casual tourist. This is an area you should only go with a specific purpose and guidance of the local police department and/or military outpost. This is not an exaggeration. If you desire to travel in these parts I strongly encourage you to rethink your plans, and if you must make sure you get the advice and support from others with experience and contacts in the area.

Focal Length

Focal length is the fourth variable of five that we will have discussed after today. The others, Aperture, ISO, and Shutter Speed we’ve previously discussed and I encourage you to review them as often as necessary to maintain a keen understanding. Next week we’ll discuss “focal distance” and from then on we’ll know and understand the five main variables and be able to refer to them as we discover exciting new techniques and methods of photography.

The “focal length” of a lens is something you encounter when perusing the specifications for any camera. On the most basic level focal length refers to the ability of a lens to magnify and image distant objects. The greater the focal length the greater the magnification. The standard measurement for focal length is millimeters. It’s important to understand that as the physical size of the film plane, or the physical size of the sensor changes, that the magnification factor for a given lens changes. There are all sorts of technical reasons for this, but for now it’s only important to understand that a 50mm lens on a 35mm film camera, crop sensor digital camera, medium format digital back, or a large format film camera will have a different level of apparent magnification. Because of this we use a “equivalent” standard when talking about cameras, reading specifications, and interpreting photography books.

Almost universally we use a “35mm equivalent”, which refers to the most popular film camera, a 35mm. In this case a 35mm camera refers to the measurement of the film, not the lens. However, we use this “35mm equivalent” so we can reference our perception of say a 100mm lens. Once we know through experience and practice how much magnification a 100mm lens on a 35mm camera provides, how far away from a standard size subject (a person for instance) we need to stand to get them all in the frame, then we can use this mental reference to refer to the focal length of other lenses on cameras with different size sensors and/or film planes.

For instance, a Nikon D300 crop sensor camera has a magnification factor of 1.5x when compared against a 35mm film camera. The same 100mm lens on a Nikon 35mm film camera, now becomes a 150mm lens when used on the D300 crop sensor digital camera. A 50mm lens now becomes a 75mm lens, and a 200mm lens now becomes a 300mm lens. When I say “becomes a XXXmm lens”, I’m talking about magnification factor only, not other characteristics of the lens.

You will notice for instance if you read the specifications for Canon’s G9 compact camera here, that it lists the focal length of the lens as “35-210mm (35mm equiv)”, but if you go to Canon’s site here it will provide the true mathematical focal length of 7.4-44.4mm! Because there are so many different sized sensors used in point and shoot cameras, we could never mentally keep track the actual perspective without a reference perspective, and universally we use the “35mm equiv” standard. Review sites, photography magazines, and other photographers will almost always refer to a lens in “35mm equiv” perspective, while often a manufacturer lists the mathematical focal distance instead.

Why are the different focal lengths? Can’t you just walk backwards and forwards from your subject and achieve the same thing? With magnification yes. But not in perspective. The focal distance (the physical distance from the film plane to the subject) used will provide a different perspective of the subject, and from one extreme can make them look wide and distorted, and the other extreme of very compressed. IT IS THE FOCAL DISTANCE THAT CONTROLS PERSPECTIVE, NOT FOCAL LENGTH.
Focal length will allow you to get closer to your subject, or further away, for a given perspective. Let’s use an example. If I stand 10 meters from a human subject and using a 24-70mm zoom lens, without moving my feet and changing the
distance, take a shot at 24mm, and 70mm, and bring them up on my computer screen we’ll see the 24mm image has the subject very small in the frame compared to the 70mm image. However, if we zoom in on that subject until the subject on the
24mm image fills the same screen space as the subject on the 70mm image, you’ll see the exact same perspective.

So why use a 70mm focal length when we could just zoom in on the 24mm focal length image and get the same perspective? Because the 70mm image will fill up more of the sensor, giving us more pixels on the subject, and therefore greater clarity, greater resolution, more contrast, and over all a much higher quality picture.

This makes some focal lengths “ideal” for certain uses. You might have already heard that a 85mm lens (35mm equiv) makes a perfect portrait lens? Some might say 100, or even 135mm rounding out the top three portrait lens focal lengths. I have all three, and if the only lens characteristic I’m worried about is focal length, then I’d choose one over the other based only on how far I wish to work from my subject. For a head and shoulders shot, a 85mm might provide 10 feet of working distance, a 100mm 15 feet, and a 135mm 20 feet. A 300mm (often used in swimsuit/bikini shoots outdoors) lens would give me an even greater working distance of almost 50 feet for the same head and shoulders framing. Of course there are other lens characteristics to be concerned with, characteristics which are easier and/or cheaper to achieve with one focal length over the other, but we’ll talk about them at a later time.

So.. 85/100/135mm lenses make good dedicated portrait lenses, and of course you can use them for other purposes as well. You’ve probably heard of a “wide angle” lens? This could be any lens from 35mm down to 12mm or less. A “telephoto” lens normally starts at 135mm and extends to 300mm. A “super telephoto” from 300-800mm and beyond.

Choosing the best lens for the task at hand can be very easy if you’re only concerned with magnification, but if you’re concerned with all the characteristics of a lens then deciding which lens can become very complicated. For instance, I have five lenses that cover the ranges from 12-35mm. Which of the five I choose for the tasks concerns everything but magnification. That I have five lenses to choose from at a given magnification, should give you some hint as to the importance of the other lens characteristics. We’ll get to that later on in this series. For now, just know that universally the focal length of a lens is referenced to a “35mm equiv” and that the “focal length” refers to the magnification of the subject related to the distance from the subject.

Photography News of Interest

With only ten days to go to Photokina Sony announced their flagship DSLR the A900. The A900 is a full frame DSLR with a 24.6mp sensor, giving it more megapixels than any other DSLR currently on the market, or even announced to the market. Sony purchased Minolta several years ago and using their designs and existing lens lineup started producing DSLRs with a Minolta lens mount and compatible metering and auto focus systems. The announcement of the A900 heralds in Sony’s intention to support the professional market. If you’ve got a bunch of older Minolta lenses and always wished they’d make a digital SLR you could use them with, then check out the A900. You can see a hands on review here.

Leaf, a manufacturer of medium format cameras with digital backs announced their AFi-II 10, 7, and 6 Medium Format Cameras with up to 56 megapixels and 3.5” LCD displays. These are true professional cameras with price tags up to $40,000 USD’s for the body only. You can check them out here.

More about choosing a wedding photographer.

High speed photography can be fascinating. Check out the GEEKOLOGIE.

Readers' Submissions

Today we have a real treat! Rob over on wanted to share his knowledge and techniques with our readers where it concerned photographing tigers in Thailand. The write up he did on this topic is extraordinary and should be mandatory reading for anyone wanting to get the most photographing tigers in Thailand, but unfortunately the piece is way too long for this section of the weekly so I’m just going to cut and paste some excerpts and a few choice images. I’m also inviting Rob back as a “guest columnist” at his convenience for the Featured Photograph and Outing topics, he’s got a boatload of experience to offer us and I can tell you from personal experience he’s a lot of fun to go on an outing with! Check out his site and enjoy the piece “On a Tiger Shoot.”

There is many a person who struggles to understand how photos of “Tigers running” is done. It certainly looks like we are in there with them, but this, like most things photographically, is an illusion.”

“What gear would be most suitable? Well it’s got to be equipment like the Nikon D2H, D3 and maybe D700 series, any of the Canon 1D2+ series and perhaps the new Sony A900. Below this there are many options, but I’d only recommend newer
models of Canons like a 50D or Nikons D300 for this kind of stuff, unless, as I have already mentioned, you are the patient type. Lenses need to be faster like F2.8 or F4. Super zooms from 28-300, for example, are generally not up to taking quality
action shots (although I always stand to be corrected).”

“Another difficult trick is the composition. Many many photos (some of the better ones too) have issues with cut off tails, cut off whiskers and the like. There are also other animals in the picture and on many occasions, evidence of the enclosure.
I am not a Photoshop buff per se (but can get around it) so I don’t spend hours on every image trying to clone out areas that I don’t like. You can do this if it pushes your buttons, but I personally like to take images that reflect
what it was like to actually be there. Strange but true.



Thank you Rob! I checked out your website and loved it! I’m sure many will enjoy these images. You’re welcome back anytime!


I suspect the readers submissions will be a highly anticipated section of this column and I encourage anyone with photographs and travel accounts they’d like to share to please send them to me at:

Readers' Questions

Hi Steve,

You could add in a question to the fireworks photo basically as an amateur photographer, what settings would I use to get the best results with fireworks at night?



Fireworks are always fun. Most compact point and shoot cameras have “picture modes” built into their programming and these picture modes almost always include a “fireworks” mode. Give this a try and see if the results improve?

If you don’t have a fireworks mode and you use a regular automatic mode, what you’ll end up with is a overexposed image with blurry fireworks. I recommend a tripod, beanbag, or other steady support and adjusting your settings as follows.

  1. ISO. Set this to the highest settings where you can accept the noise. On a DSLR ISO 1600 will give great results with fireworks.
  2. Aperture. With fireworks you don’t need to be concerned with depth of field (DOF) because the fireworks are so far way. Choose the widest aperture that normally provides good results, say F4 for instance. This will allow the minimum shutter speed.
  3. Now, frame your scene and adjust your shutter speed so the sky is dark (vs. an overexposed orangish color), and the fireworks are properly exposed. You’ll find you can use a pretty short shutter speed and capture great images of the fireworks suspended. You can also ‘drag’ your shutter and catch the fireworks falling and blurring together, but be sure your camera is will supported so your entire image isn’t blurry.
  4. Auto White Balance is usually sufficient for fireworks, but if on your LCD you see colors that you don’t agree with, adjust your white balance until the colors are as close to real as possible.

I hope this helps. I’ll be taking some sample firework pictures next time we have them here and I’ll share those with more instructions in the future.

Hi BKKSteve,

I was meant to post this question way back when you covered ASA/ISO, but now you have already done shutter and aperture!!

Anyway, not bothered if this gets posted or not, just want to dip my toe into your font of photography knowledge (FPK).

ASA indicates the sensitivity of a particular film to light – understood.

ISO is the same thing for digital cameras.

Herein lays my quandary. We do not have film in a digital camera, only a sensor of some description. Therefore, why do we not only have shutter and aperture to worry about and not ISO? Basically, what does the ISO on a digital camera relate to?

Many thanks, keep up the good work, it's a great addition to Stick's site.


Shaun –

Nice to hear from you.

Thanks for the question. I’ll answer it here and in next Saturday's weekly because if you have this question I’m sure others do as well and could benefit from the answer.

Film has the ASA value and as you know we’d buy different emulsions of film with a different sensitivity to light. 25-6400 ASA was commonly available.

Sensors of course aren’t changed out like film, there is only one sensor in a given digital camera yet it has an ISO “range” that might be from 50-12,800 or more in the newest digital cameras. You’re asking “what does the ISO on a digital camera relate to?” and since I’ve already said in the column that you can equate ASA to ISO values directly between film and digital cameras, you must be wondering what changes with the sensor since it’s the same sensor, while with film we’re putting in completely different films to achieve different ASA’s?

Think of the sensor in a digital camera has an stereo amplifier. It has a volume knob where you can adjust the volume to a range of settings which takes the input from your CD player (think of this as light into your camera) and amplifies it through a range of adjustment (think of this as the range of available ISO values), producing a different level of sound from your speakers (think of this as the image on your computer monitor). At the lower settings the sound will be most smooth and pure and free from distortion, but as you crank up that stereo to higher volumes you induce clipping and other forms of distortion. A digital camera sensor is capable of producing different levels of sensitivity to light (from the same sensor), however you sacrifice different levels of output quality. In the case of digital camera sensors this would be detail, noise (like film grain), dynamic range, and more.

I hope this helps.


Please submit your questions to All questions will be answered and most will show up in the weekly column.

A Snapshot of Bangkok Images Week in Review

As I write this I’m traveling in southern Thailand with a client and I hope to have a lot of new material to share on my return. We’ve visited the Siracha Tiger Zoo to practice telephoto and autofocus techniques in regards to photographing wildlife, and we’ve visited the Khao Kheow Open Zoo to work on the same techniques. Usually I leave my own camera behind and give 100% of my attention to my student, but this time he only needed limited instruction, and the animals were especially interesting, so I spent a bit of time taking my own photographs which you can check out in the gallery section of my website under the Pattaya category. There you will find two new galleries with images from both places we visited. I hope you enjoy them.

Mirrored Blog

I haven’t had time to sort out my blog issue yet, but I hope to get to it week after next and to be able to bring you more of my archived blogs.

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