Today's article is going to cover Lenses

(for those of you wondering about the dynamic range two parter, I plan to sneak over to one of my clients homes being held open and actually walk through the solutions within the same room. Yay, a field trip! - that will be later however).

I'm going to talk in a general way about lenses. Much of the lens information will apply to all camera's though by necessity some of it will specific to the DSLR format.

First off, I'll describe the basic categories lenses usually fall into:

• Wide Angle: These are your workhorses when it comes to shooting interiors. Generally speaking these lenses fall into the 10-24mm range. They will be both zoom lenses or primes (a prime is a fixed focal length lens, i.e. it doesn't zoom). Even the best wide angle lenses have trouble duplicating the quality of standard or mid range telephoto. You can expect some degree of optical distortion from all of them.
• Standard: These lenses are generally in the 20-85mm range. You will find very high quality lenses in this category, particularly primes. The focal length between 35mm and 50mm most approximates the actual scene the eye will see. A 35mm lens (sometimes a 50mm) is called a 'normal' lens for this reason. If you aren't sure what focal length lens to get for general photography, consider something in this range...it's good for a lot of different types of photos. 
• Mid Range Telephoto: These fall generally into the 70-300mm range. Between, oh...about 70 and 130mm is the best focal range for shooting people (portraiture). The natural distortion at these lengths is very flattering to the face. Most of these will be zooms but there are still some primes. We can zoom pretty far with these (not quite into stalker territory yet but close). These lenses will have high optical quality though not typically quit as good as standard lenses. You might also want to keep in mind that these lenses are starting to get big, and heavy.
• Super Telephoto: Yowza...these lenses are big, heavy, and expensive. 300-1200mm (and up). You can expect to pay a lot of money for these ($12K in some instances). Generally these are popular among sports photographers, birders, wildlife folks. Optically some of these lenses are very good though again, not matching standard lenses.
• Macro: Macro lenses allow you to shoot very small objects that then appear big (hence the term macro = large, sometimes confuses folks). Typically these just allow for a 1:1 subject to sensor ratio.
• TSE: Ahh...the Tilt Shift. If you have actually stuck with me this far and aren't passing notes to suzie you are in for a treat. A TSE can be an essential lens for real estate photography. Ever angle your camera to get the whole room in view? Sure you have. Well what happens to the vertical lines in the room? They start to angle upwards, or converge. This is called Keystone Distortion. It doesn't look good (unless done for artistic reasons). A TSE actually allows you to 'shift' the lens upward, moving the film plane parallel to the sensor. It's more complex really, but the point is it handily solves that problem.
• Other: There are other speciality lenses (Holga style lensbaby for example) but I won't cover them here. (this dang article is getting long enough...it's like a Stanly Kubrik film already).

To the left (and one on the camera) are three of my favorite lenses which I use for both real estate and portraiture.

The big white whale on the far left is a 70-200mm zoom. It's aperture is 2.8 which means it's fairly fast (we'll talk more about that later). It's image stabilized and has excellent optical quality. One of the finest mid range zooms money can buy. It's also dang heavy and very conspicuous. I use this lens primarily for working with people / portraiture.

The middle lens is the super 17-40mm wide zoom. It's aperture is 4.0 which is on the slower side but I couldn't care less as I stop it down to f11. 90% of my real estate work is shot with this lens. It has outstanding wide angle performance. This is also my primary landscape lens.

On right is a 24mm TSE (note the little extra knobs which allow the lens to shift). This is a prime, or fixed length lens with excellent optical quality. It's also not very fast but I'll be at f11 again so no worries.

On my camera itself is an 85mm portrait lens. This is a fast lens that fits perfectly into the sweet spot for shooting portraits. 90% of my portraiture work is done at 85mm. 

Wow, are you still here? Do you need an intermission? I do!

Ok. I'm back. I know this isn't the most exciting topic in the world but hey, we are learning stuff here.I will throw in another pic to break this up a bit. The below was shot at 17mm with my primary real estate / landscape lens. That's Seattle and the Olympic mountain range in the distance.

I've got to cover lens basic features and then we can wrap up:

• Aperture: Ok, this is the biggie! Aperture is a ratio of the size of the place where the lens lets light in, to the size of the lens itself. Well, what's the big deal about that? That opening tells us a lot about how the lens will perform. Because it's a ratio we know that smaller numbers equal bigger apertures, right? So a 2.8 is bigger than a 4.0 and a 1.8 is bigger than a 2.8 and so on. The bigger the aperture the more light the lens will gather in a short period of time.However, there's a warning...the bigger aperture will also be have a more narrow depth of field. In other words, the background will blur more (this is called boke and is a whole article in itself). So, let's see if I can summarize.Small number = big aperture. Big aperture = lots of light quickly. Lots of light quickly = only a small section of the photo will be sharp.Make sense? BTW you can set the aperture to be smaller than it's max but you can't make it bigger. That's why 'fast' lenses command such a high price. For portraiture a big aperture is essential. For real estate you want to be at around F11 for plenty of sharpness. 
• Focal Length: I think we covered this for the most part but but just a recap. All lenses provide some distortion at a given length (though 35-50mm is pretty much spot on to what the eye sees). Not all distortion is bad (for example in portraiture).
• "Resolution":All lenses have a realistic ability to resolve only so many 'lines'. If you drop a pile of cash on a high quality camera you'd best get some high quality lenses...or the lenses wno't be able to supply the actual resolution of the camera with usable light. Bummer!
• Elements: Many lenses (especially zoom) have a whole bunch of glass (or other exotic materials) elements. Just remember, more elements = higher cost, higher weight, and more likelihood of 'flare' (flare or those annoying bouncy bits of light).
• Autofocus:Most lenses today come with pretty dandy autofocus capabilities. Two things to remember here, most people like full time manual also (meaning you can just reach up and focus with your hand even in auto mode) and also the drive mechanism should be ultrasonic if possible (extremely fast, accurate, and quiet).
• Image Stabilization: This is another one people debate a lot. Stabilized lenses have a device inside that measure camera shake and actually moves the elements of the lens accordingly. This helps you capture an image sharply that would otherwise be too soft. Neat huh? Well, mostly. It's a real help at times but not a miracle worker. It also adds a lot of weight and cost to a lens, plus it drains power. One thing to note is that some manufacturers put the stabilization in the body...making all lenses stabilized.  This is great from a weight / cost standpoint but it's not optically as good.

Ok, I think this article is starting to exceed any reasonable standard of length. ;)

There's a lot more I could cover but this should get you off to a good start. At some point I'll probably try to cover boke (often transliterated as bokeh) and aperture in their own separate articles.

Cheers, -B

Real-Estate-Photography