Monthly Archives: April 2010

Digital Photography Course #2 Focal Length: What Lens to Use?

IMG_0364brder

Before you read this, please go through the first article: Course #1
And here’s a secondary disclaimer: I can’t teach you how to take good photos. I can only try to teach you how to use the tools for you to ‘try’ to take good photos. I’m still trying all the time myself! Besides, a good photo is entirely entirely subjective!

Focal Length
The age old question: “Does size really matter?”
The answer: Yes! Yes it does! Though the real answer is ‘Length’. Or the Focal length of a lens. But before I can discuss focal length, I must define what a ‘lens’ is.
Lenses, work just like your eyes. Light comes through and it focuses it into an image in the sensor. Zoom lenses are typically more complicated, as are wide angles. Think of it as a ton of light coming through, and smart engineers have to bend, refract, reflect, and all the stuff you never really cared for in Physics, to get that image to go through the sensor without distortion.

For example: this is what goes into a Nikon’s 70-200mm.
70-200
And part of the reason why that lens costs around $2000 USD.

Lenses come in two flavors: Zooms and Primes.
Primes, are generally lighter and less complex than their zoom counter parts. As such, they generally have higher apertures. For example, the internals of an 85mm.
85

How to read a lens:
IMG_9918
Note it says: 85mm 1:1.2

This means it’s a prime lens. Its’ focal length is only 85mm, and the highest aperture it goes is 1.2.

IMG_9920
Note it says: 24-70 1:2.8

This means it is a zoom lens. It’s widest is 24mm, and it can zoom up to 70mm. And the highest aperture it can go, on either end of the zoom scale is F2.8

Take a look at your lenses, they are usually marked at towards the barrel of the lens. Some lenses say: 18-55 1:3.5-5.6
This means at the lower end of the zoom. 18mm. The highest aperture you can go is F3.5 As you zoom in towards 55mm, your highest aperture is now 5.6.

The more you zoom, the less light can come into your lens. It’s much harder for those geeky engineers to defeat physics.

Authors Note: That is why generally zoom lenses with a single fixed aperture are so large and expensive. It takes giant glass to be able to suck enough light in, and
account for the differences at each end of the zoom spectrum. My 24-70mm looks like a mini rocket launcher and weighs a ton. But in actuality, it’s just a 24-70mm lens.

Back to the original topic
Ok, enough about the lesson in lens characteristics. The topic of this course is Which lens do I use? and why
The short answer is, you use whatever the heck you want to use. However, as with every discipline, there are guidelines.

14mm, is a bit wide for my tastes. It does have distortion towards the edges, and thus, I avoid using wide angles for anything other than landscapes, or if I want some wonky effects when shooting people. But on that note, the wider the lens, the larger the separation between the subject and the background is. It’s a matter of perspective

Too illustrate the point.
IMG_9924
This is my good friend Optimus Prime, shot at 14mm. Notice the background and subject look pretty separated.

IMG_9925
Now shot at 24mm:

IMG_9929
Now shot at 200mm:

Trying to keep the subject the same size, I had to physically move backwards. Hence, my perspective has changed. Note, at that distance, using a 200mm lens, the optical illusion is that the background background appears to have moved much closer to the subject, or appears compressed. Contrary to popular belief, perspective isn’t a matter of what ‘focal length you use, but rather…where you place the lens. It’s not really compression, just perceived. Again, it’s just a matter of perspective. Ansel Adams repeats so often in his wonderful book, The Camera: “perspective is a function of camera-to-subject distance.”

So what does this mean in the real world? You can apply this to landscape photography, or portrait photography. When I shoot portraits, babies, dogs, etc. I like using 70mm, 85mm, or even 200mm focal lengths. It makes the subject a bit more pronounced. I want the subject to be dominant.
gbfx-54

GBFX0131

The same principle can be applied to landscape photography. When you’re shooting a picture of a mountain. Do you want a wider angle shot? The background will be small, less daunting. Or do you want to shoot it at 200mm, and the mountain you’re shooting will appear as if it is much closer than it is. Much more larger, grander, in scale? That all depends on how you want to shoot the scene.

in conclusion
Zooms and primes, each have their place in life. I used to have more zoom lenses, but I’ve since sold most of them off. I only have two left. The 24-70, and a 70-200. The rest of the lenses seen above are all primes. It’s a matter of preference. Zooms are more versatile in wedding or fast past ‘event’ driven photography. Whereas primes, (at least for me), work for everything else. Unfortunately, you need to switch lenses back and forth if you’re dealing with a prime lenses, depending on the situation. A zoom on the other hand, can just be used as is. I personally think zooms make you lazy. You don’t have to move, or think about things as much. In contrast, primes force you to move forward, backwards, trying to get you to think more about the angle of attack. But it takes some getting used to. If you’ve been reading my blogs for the past 2 years, it wasn’t until fairly recently that I was comfortable enough with myself to move to nearly a full ‘prime’ setup.

For multi-purpose shooting, I prefer a 35 or 50mm lens. Landscapes, obviously I’m a wider 14mm or 24mm type of guy. Portraits (single person), I’m a fan of the 85, 70, or 200mm variety. For family or group shots, I prefer 35, or 50mm. Sports shooting, well there’s no matter of preference there. I need all the reach I can get, so I generally grab a 200 or a 300mm prime for that.

So the million dollar question? What lens do you buy next?
Well, here’s a tip. Do not go out and buy this lens: 120mm F5.6
It costs $99,000.00 (yes I have the correct number of zeros). I guarantee if you bring one home, you will get a nice divorce. However, if you do have money to burn, you can impress your spouse by shooting images up to 2 kilometers away!! So the good news, is while your filling out the divorce papers, you can spy on other houses far away, as soon as you get kicked out of yours!

Well before you make your lens choice, you must know about your digital camera. What kind of crop sensor does it have? People who come from a film background really are not used to this. Film that is used is generally 35mm,(the width of the physical film). And lenses, are as they appear to be. However, most digital cameras are 1.6x crop. What does that mean? It means it has a smaller sensor size.

(these are rough numbers, actual numbers vary by manufacturer)
A full frame sensor is: 36mm x 24mm
A 1.6x crop camera is: 22.5mm x 15mm
A 1.3x crop camera is: 28.7 x 19.1mm

The smaller sensor size means: it is cheaper to manufacturer. Silicon to fill a full frame cost a boat load of money, they actually stitch the silicon together. Therefore during the manufacturing process, it is more error prone, and much more costly. To get an idea, one of the first standard full frame digital cameras to hit the market (The canon 5D, cost nearly $3k) at the time. A 1DsMKIII cost roughly $8k, when it was introduced, compared to it’s 1.3x brother, which was only $4k.
Yes, full frame digital cameras are expensive. But…what you gain from them, is more like shooting with film. Your lens, focal length is what it is, not hampered by the dreaded focal length multiplier

To illustrate, here’s a picture I recently took at the Academy of Sciences in San Francisco.

focallength
Notice I drew out a rough diagram of the sensor size, and what you would see for a 1.6x crop, or vs a 1.3x crop, vs a full frame.

So if I used my my 20D camera and shot a picture of the frog. I would get this image:
1.6x

Whereas if I stayed at the EXACT same position, and used my 5D camera, I would get this image:
ff

Nothing has physically changed in terms of distance. But, because the sensor on the 20D is smaller, it seems as if I zoomed in just a little bit. Hence, why they call it the 1.6x crop factor. What this means is, for every single lens you buy. You have to multiply it by 1.6x, and that will be the focal distance that you are ‘really using’.

Lets say you bought a 50mm lens on your shiny new D90 or 7D. You take 50mm x 1.6 = 80mm. That means your 50mm is roughly the equivalent of my 85mm lens on a full frame camera. If you bought an 35mm lens: 35×1.6=56mm. That’s why a 50mm lens may not work too well in a small room indoors. It will, get good portraits though of their faces! But if you want full body, you’d need a much much wider lens on a crop camera. Kit lenses that come with the camera are generally 17-55 mm. Or 17-85. It covers a good range, (remember to multiply that by 1.6 on your crop cameras). I avoid kit lenses because they’re typically too slow for my line of work. F3.5 indoors where they do not allow flash is not fast enough. However, there are Image stabilized (IS) lenses that cover that range, which I hear are pretty good.

Here’s a list of the cameras (to my recollection). I’m sure there are more out there, and I really don’t care. This is just to provide general information.

1.6x APS-C format sensors.
Nikon calls it DX format which is 1.5x crop
Canon’s are just APS-C: which is 1.6x crop
modelsCanon: Rebel xti, 10D,20D,30D,40D,7D
Nikon: D40, D60, D80, D90, D300

1.3x
Nikon: I don’t believe have a 1.3x crop body
Canon: calls it AP-S sensor
modelsCanon: 1D, 1DII, 1DIIn, 1DIII, 1DIV
Nikon: n/a

Full Frame
Nikon calls it: FX
Canon: just calls it full frame.
modelsCanon: 5D, 5DII, 1Ds, 1DsII, 1DsIII
Nikon: D700, D3, D3x, D3s

Advertisements

Digital Photography Course #1

A buddy of mine recently purchased a Nikon D90, and is pretty new to digital photography.  I figured this would be an excellent time to get back to the roots of this blog by writing a quick primer on the most essential basics of Photography.   I can’t teach you how to take good photos, however I can teach you what it takes to take a photo.  Whether or not it’s good or not is quite subjective and beyond the scope of this tutorial.

So what is photography?  An artist would say, “it is painting with light”.
A philosopher would probably say, “capturing discrete moments in time, never to be experienced again”.
An engineer would probably say, “Given the distance to subject at x, and lighting coming from 4 different sources, to achieve a proper exposure at F2.8, one would need to be at 1/4000th of a second, at ISO 200”. Makes you really want to smack that engineer upside the head. Photography doesn’t have to be that complex, nor should it be. It just takes the spontaneity out of it.

That, in a nutshell, lies the beauty of photography.  It blends many different disciplines, and rolls it into one simple package.  As we all know, generally in it’s simplicity, lies an abundant amount of complexity  waiting to be explored.   It is my therapy from a stressful day. The sheer joy of Creating something, that something that can bring enjoyment to yourself and to your friends/families is very rewarding.

I find most people find digital photography very daunting.  There are soo many options, buttons, settings, features.  It’s quite mind boggling when you think about it.  However, my answer to that would be, eliminate everything, avoid all the complexity, and the key item that remains is:  “Exposure, Exposure, Exposure”  (Yes, it’s a derivative of the old real estate maxim, “Location! Location! Location!”).   Doesn’t matter if you have a fancy four thousand dollar digital SLR, or an old film camera, or just a simple point and shoot.  The principles are identical, and nothing has changed for a very long time.

What is exposure?  How does one measure it?  For the purpose of this document, I’m going to be basing my exposure on the use of the camera’s built in light meter. (aka the reflected light meter)
In the canon models, the light meter is that thing on the bottom of your camera. Looks sorta like this:
canonlm

And the Nikon looks like this:
nikonlm

Again, to avoid complexity, I’m not going to get into the metering modes, and all that jazz. All you need to know, and all you care to do. Is to make that line be close to the center as possible. The zen of photography, is balancing 4 variables, to get to the middle, or as close to the middle as possible.

For canon cameras, as you notice, it is in real terms. Negative being on the left side, zero (or zen), and positive on the right side.
If you notice in the Nikon photo above, you may ask yourself, why is it ass backwards? In Nikon land, Negative is on the right side, and positive is on the left side. Doesn’t really matter who’s right or wrong, what matters is the end game for both systems is the same. To reach the state of zero. An experienced photographer can reach the state of zero, and generally know what settings to put the camera in zero state, much quicker and adapt to changing lighting conditions much better than a novice photography.

Authors Note: To put things into perspective, the difference between a 500 dollar camera, and a 4000 dollar camera. The difference between a $200 r lens vs a $2000 lens is their ability reach zero in less than ideal conditions. Any camera can take a picture in sunlight under ideal conditions. However, not everyone can go into dark interiors, or dusty environments. To shoot in cold or wet conditions, etc.

So how does one reach zero? To achieve exposure, there are 4 variables: 

1. Aperture: aka f-stop is the iris of the lens. Think of them as fancy blades. The diameter of the blades are expressed in f-stops.
blades
As you can see in the picture, the blades open or close, therefore controlling the amount of light that enters into the film/sensor. (From now on I’m going to refer to it simply as “sensor”). Photographers generally complain: “My lens is too slow”. No, this doesn’t mean your lens can’t win in a horse race. It means when shooting wide open, (the maximum aperture your lens can go). It simply does not let enough light in, to reach zero state. The faster the lens, the closer to zero your number will be.
You will see that photos are described as shot using: F2.0, F5.6, 3.0, etc. (again, to avoid complexity, I’m going to stay away from the mathematics behind these numbers). You can achieve nifty effects with this variable. (Blurring, sharpening, etc, but I’ll get to that at a later date, today is just trying to get people to reach zero).

2. Shutter Speed: Aka “The curtain”.
Think of this as a curtain that slides up and down. The faster the curtain moves, the less light gets into the sensor. The slower, or longer the curtain remains open, more light is let in. As you can surmise, there is an inverse relationship between aperture, and shutter speed. Meaning, the wider the iris (lets in more light), the faster you have to set the shutter speed to limit the light going into your sensor…in order to reach zero. Conversely, the smaller the iris is set, less light is allowed in, therefore, you have to open your shutter speed much longer in order to let more light in, in order to (you guessed it… reach zero).
This number is expressed in seconds or fractions of a second. 1, 2, 3, 1/100, 1/1000, etc.

Authors Note: Generally cameras maximum shutter speed is 1/4000 of a second. Higher end cameras go to 1/8000 of a second (translation, very very fast).

3. ISO: Is the International Organization for Standardization. In the land of photography, it is expressed in a number that represents the sensitivity to light. Expressed in 50, 100, 200, 300, 400, 800, 1200, etc.
What on earth is sensitivity to light? Well the lower the number, the less sensitive to light it is. In very simple terms, the sensor in your camera doesn’t such in ‘that much light information’. The higher number you go, the more sensitive to light it is. So you ask yourself, well why not put it at the highest number possible?! Then you can shoot in darker conditions right? Well the answer is, because there is a trade-off. The more sensitive it is, the more ‘grain’ or ‘noise’ that will be in the image. Think of your sensor working in over-drive. Trying to suck in as much as possible, and that includes grain, fuzziness, and noise. Yes, that means if you shot at ISO1600 or so for awhile, it does tend to drain your batteries a little more (not my much), and it takes longer for your camera to ‘process’ a shot because most cameras have algorithms to pre-filter out the noise that will also come into the image due to the extra ‘sensitivity’.

Authors Note: Point and shoot cameras are generally are utterly useless at ISO 400 or above. The small sensors can’t handle that much. Entry level DSLRS, generally go up to 1600, ISO 3200, but in terms of ‘usability’. I try to stay within the realm of ISO 800 or 1000. Higher end cameras and new cameras can have ISO’s that go up to 6400 and 12800. With even better algorithms and fancy magic voodoo sauce to mitigate noise. For me, if I’m shooting indoors, I know my cameras peak out at ISO 2000 or so, so I try not to ‘push’ it beyond that, otherwise I’ll sacrifice image quality. Your camera may vary, and I suggest you play around with the setting to see what your camera’s ‘limits’ are so you know how much you can push it.

4. Focal Length: Now you may think I’m crazy, but bear with me here. What is focal length? Focal length, is your lens. Expressed in mm or millimeters. (Yes, the world uses the metric system, and our backwards ass country still uses inches and feet. *sigh*. What is mm? You see it all the time. A 28mm lens, a 14mm lens. A 200-400mm lens. What on earth is it? Well, it’s actually the distance between the lens, and your sensor/film. Take your hand and place it right in front of your eyes palms flat. If your eyes are the ‘sensor’, and your palm is the lens…if you notice, the closer you move to to your eyes, you see ‘more of your hand. A much more wider perspective. Conversely, if you move your hand further away from your eyes, you start to get a more myopic view. Translation? The smaller the number, the wider the view. The larger the number, the closer you are, but you don’t get much of a ‘wide’ point of view. So a prime (or fixed focus lens is expressed by a single number).
28mm, 14mm, 200mm lens. A ‘zoom lens’ has 2 numbers. 24-70mm. 70-200mm, etc.

Back to the topic at hand. How on earth does focal length affect my ability to reach zero? Simple! The more zoom you have in your lens, the more you will notice the effect of ‘camera shake’. That’s why lenses that are 200mm or so have image stabilizers. Because any ‘slight’ movement, means you will shake shake shake yer booty.
Wider lenses, shake much less, due to the field of view, any camera shake is much less noticeable. My rule of thumb…always multiply your focal distance by 2. And that’s the minimum shutter speed you need to be at before you shaking effects you. For example, if you are shooting with a 50mm lens. In order to not get blurry images, you have to shoot at 1/100 of a second at a minimum. You can go below this if you have maaad steady hands, but this is just a ‘general’ rule.

Take another example, if you have a 14mm lens, well you just have to be shooting at 1/28 of a second to mitigate shake. What a difference it makes huh? 1/100 of a second lets is much faster (lets less light in, than 1/28 of a second). Conversely, if you’re shooting a 200mm lens. At a minimum, you should be at 1/400 of a second.
That’s a huge difference, because if you’re shooting at night, you need to let all the light in you can possibly muster. And 1/100 or a sec, or 1/400 of a second won’t let enough light in to get a proper exposure.

Tying it all together!

Practical Applications: (AKA use cases).
indoors:
So you’re cruising around with your 50mm lens shooting pictures indoors at your child’s piano recital. There’s not a whole lot of light and your indoors. So first thing you should so is set your ISO to 800. (Or whatever you think your camera can do before it makes too much noise). Well you have focal length, and you have ISO. That leaves 2 variables left! Knowing what you know, about the focal length multiplier, you now have to be sure that your shutter speed is at 1/100 of a second. With this set, you now will have to look into your light meter, and see where that needle is at. Is it under exposed? (too little light) Or is it over exposed (too much light). You now bring aperture into the equation. Most parent’s digital kit lens has a maximum aperture of F3.5 (kinda slow for my tastes). So you set your aperture as high as it would go (f3.5) and look at that meter. If it’s still below, well, now you are at a cross roads. Do you bump the ISO sensitivity to allow for more light in but sacrificing noise? Do you lower the shutter speed, to let more light in, potentially causing image blur? It’s up to you.

It’s more of like a ‘choose your own adventure book’. If you choose poorly, your wife will be upset because you didn’t capture the moment of your kid’s recital. Then you will be forced to sleep on the couch. (One good reason to hire a professional! =) I generally calculate all these conditions and set things on the fly, and you have to do this in split seconds as events and lighting conditions change and unfold (these things come with experience and time). For now, feel free to shoot like a granny. Take 4 or 5 minutes to adjust your settings, to reach zen. It’s ok, after a few more recitals and better photos later, your significant other may let you back into the bed!

2. outdoors
It’s a bright and beautiful day, the sun is shining, the flowers are singing. And…oh crap, your kid has a soccer game, and you’re responsible for taking photos. Nghia, Your favorite photographer is no where in sight, so you have to man up and do it yourself. Well first of all, it’s sunny as heck outside, so you want to set your ISO to it’s lowest possible setting. ISO 100 for canons, and I believe Nikon’s minimum is 200. The last thing you need is something more sensitive to light because you don’t want to overexpose your image. Next, you pick your focal length. For soccer games, you want to get into the action, so cameras with 55mm or less just won’t cut it. Usually for sports I go with 200mm, or so, and even then that’s not enough reach. Rich ass parents have shiny 300 or 400mm lenses (that they don’t know how to use).
For the most part, a kit lens may go up to 55, maybe 105, it really depends. So, you have your aperture, you really want to take nice blurry background shots, so you set that aperture as wide as you can. (F2.8, F3.5, F4.5, whatever your lens goes to). Check the light meter, and then move your shutter speed accordingly until it reaches zero, then snap! Done!

3. Every spouse’s nightmare
So you have a brand spanking new baby. You are a zombie, you can’t sleep, so you get into reading about photography and stumble upon this blog. You want to take cool photos of your baby, but can’t afford to hire ‘yours truly’ because you spent all your money on diapers. What do you do? Well flash photography hurts your baby’s sensitive eyes. You tell your wife, you don’t want to use flash. You set your aperture at F3.5 and you go down as low as you can go on shutter speed, while maxing out your ISO at 800. Yet it’s still too dark, and you are missing precious moments, feeling very inadequate because you are unable to capture the shot. You show the dismal, dark photos to your wife, and she throws you back into the couch, then rips up the photos in disgust.

What do you do??! Well, you have a brilliant idea! You now have an excuse to get a faster lens! Yaay! I recommend the 35mm prime, F2.0, or if you can afford it, a 35 F1.4. Now you know that F2.0 or even better, 1.4, can let much more light in! the iris opens nice and wide, so you are now able to snap awesome pictures of your precious little baby…But wait! There’s more! You then convince your wife you clearly need a better camera body. You want one that has higher ISO support for cleaner images so you can shoot even better more fantastic photos of your baby in their dark dungeon of a room! Yaay another new toy! OOhh…and then you realize, man they’re growing up, and the baby is starting to crawl, and walk and run outside. Auugg, now you need yet another lens to keep up with the baby’s wild antics! Bruhahhaha… now you’ve spent thousands of dollars, but the good news is. Now you have an excuse! =)

Authors note: What I generally do is judge the scene, first thing I do is evaluate my surroundings and set my ISO first. Indoors, I go to IS0 600, 800, etc. Outdoors, I put it at 100 or 200. Then I set my aperture. Why? Because aperture, controls the mood of the image. Blurry smooth photos? The lower the f-stop setting. Sharp, group photos, the higher the f-stop. Once I have those two variables in play, the last part of the equation is adjusting my shutter speed to get the proper exposure and then snap.

And that, ladies n gentleman, is photography in a nutshell.
Disclaimer: This is assuming you set your camera to Manual Mode. The only mode I shoot in. If you set to Auto, well, the computer makes all the decisions for you depending on the conditions, but as we all know. Nothing beats the expressive nature of our minds, and there are just some things the computer, no matter how powerful, can replace or simulate.

Related Links: