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Digital SLR Guide News, Feb. 2007 - Finding the Best Digital SLR Lens
February 27, 2007
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Digital SLR Q & A
Question: How do shutter speed and aperture work together?
Last month we tackled the concept of shutter speed, and talked about how you can control the amount of light that strikes the digital sensor by adjusting how long the shutter stays open.
If the shutter is only open for a fraction of a second, not a lot of light gets through. When your shutter is open for several seconds, it allows a LOT of light to get through.
Like apertures, shutter speeds follow a standard scale, and aren't just any number you can think of (1/234 is NOT a valid shutter speed). The shutter speed scale looks like this (with shutter speeds getting slower from left to right):
Shutter speed and aperture are the two ways that you can control the quantity of light that actually makes it to the surface of your digital SLR sensor, and the two act in conjunction with each other to create an exposure. There are three different ways that ain image can be exposed:
The goal - of course - is to always capture photos that are correctly exposed.
Think about it like this: imagine that you're trying to boil water instead of taking a picture. There are two different ways that you can bring the water up to the ideal temperature: you can turn the flame on full blast for a short period of time, or you can turn the flame on low for a long period of time.
The end result is the same: the water boils.
In a similar fashion there are two ways that you can get a correctly exposed photograph: you can open the aperture wide open for a short period of time (fast shutter speed) or you can keep the aperture narrow for a long period of time (slow shutter speed).
Think of a proper exposure like a balanced scale: aperture and shutter speed are in perfect synch with each other. But if you change one of the variables, then the other must change as well to keep the balance correct. Here's this relationship expressed a different way:
Understanding this relationship is fundamental to a more detailed discussion of exposure, so I'll leave you with that for now. Now that you know more about aperture, shutter speed, stops of light and the aperture/shutter speed balance we'll be ready to dig in to a discussion of manual exposure next month.
Online Digital SLR Lessons
Learning ResourceThis learning resource is less about education and more about inspiration.
I believe that there are three fundamental ways that you can learn how to take better photos:
The learning resource for this month falls into the third category, since the photos on the site are not only amazing, they're also inspirational.
The site is called Sensitive Light, and it's an online gallery of a fellow named Graham Jeffery.
Whenever you find an interesting photography site like this one, I suggest you follow these steps if your end goal is improving the quality of the photos you take:
For example, I was quite taken with the colored smoke gallery, and that inspired me to try capturing my own photographs of smoke.
While my initial results were less than spectacular, I learned a great deal about what it takes to photograph smoke (it's a LOT harder than you might think) and I was able to practice taking a wide variety of photos - which is never a bad thing!
How and When
How to Take Photos For Large Print Sizes.
Let's get this out of the way first: the dimensions of most digital SLR sensors are identical to the dimensions of a 4x6 print (see photo at right).
The relationship between the long and short side of your digital SLR sensor is called aspect ratio, and is typically expressed like this: 3:2. This indicates that the sensor is shaped like a rectangle. If it were square, the aspect ratio would be 1:1.
You'll notice that if you multiply both number of the sensor aspect ratio by two that you get a nice match with a 4x6 print: 6:4.
This is why when you make 4x6 print of photos captured by your digital SLR, you don't lose any part of the image. The photo that you take is the photo that will print.
There are some notable exceptions to this rule: any digital SLR camera made by Olympus. Rather than a 3:2 aspect ratio, all of the Olympus sensors are set at 4:3. If we multiply this aspect ratio by 1.5, we wind up with 6:4.5. Since this does not match the dimensions of a 4x6 print, it means that every 4x6 print you make from an Olympus digital SLR will crop off approximately a half inch of the original image.
But what does this all have to do with large print sizes? I'm just about to get to that.
Let's say that instead of a regular size 4x6 print, you've got a photo that's worthy of a blow-up. You decide to make two prints, one at 5x7 and the other at 8x10.
Let's get back to our 3:2 aspect ratio. If we multiply this by 2.5, we wind up with 7.5:5. See where I'm going with this? If you make a 5x7 print of a photo taken with a 3:2 sensor, you're going to have to cut off about a half an inch from the original image (view photo).
But an 8x10 is even worse. Multiply the 3:2 aspect ratio by 4, and you wind up with 12:8. You guessed it - when you make an 8x10 print of this, you're cutting off a full two inches from the original image.
Imagine that your original image is a portrait and that you got up nice and close to your subject, completely filling the 3:2 frame. This image looks great on your monitor and it's going to print well at 4x6. But if you intend to print it at 8x10, you're going to severly cut in to your well-composed portrait - maybe even losing part of your subject's head (view photo).
What's the solution to this problem? There's two parts to it:
The end result here is that you've just given yourself more breathing room around the edges of your digital image. If you do decide at a later date that an 8x10 print will look spectacular up on your wall, you've got plenty of room to crop out those 2 inches while maintaining the flavor of your original composition.
Cameras and Accessories
Latest Digital SLRIt's not surprising at all that I have no new digital SLR news this month.
The reason is a simple one: the beginning of March also marks the digital camera event of the year: the Photo Marketing Association (PMA) conference and exhibition.
Many manufacturers will leak information about new products prior to PMA, but this year has been exceptionally quiet, except in the compact digital camera market, where there seems to be three new cameras a day.
Expect that all to change once PMA actually takes place. Digital camera manufacturers use PMA to not only show off new products that will soon be available to consumer, but also to "preview" advance release models and cameras that are still under development.
Since that's the case, you'll just have to wait until next month's newsletter, at which point I'll report about any new camera models that were announced.
PMA 2007 runs from March 8 to 11 in Las Vegas, Nevada.
Digital SLR Camera of the Month
It's not that it has strange settings or that it operates all that differently from other cameras...it's just very hard to pin down what this camera EXCELS at.
Let me explain.
Compare the Nikon D80 to other 10 megapixel digital SLR cameras: the Canon 400D, Sony A100, Pentax K10D and Samsung GX-10. All the rest of the cameras in this class have at least one additional special feature that sets them apart: self-cleaning sensors (all BUT the Nikon), built-in anti-shake (included with the A100, K10 and GX-10) and all-weather sealing (available with the K10D).
Given this, you might expect the D80's performance to be superior to the rest of the cameras in this list in some significant way.
While die-hard Nikon enthusiasts will argue that its performance IS superior, the camera specifications don't really illustrate where these differences lie (and in the end, they might be more subjective since Nikon is such a dominant brand).
Its 10 megapixel sensor, 11-point autofocus, 3 photos per second shooting speed, ISO settings and color adjustment are all equivalent to every other 10 megapixel digital SLR camera, save one.
That one camera also happens to be a Nikon: the D200.
The D200 beats out all the other 10 megapixel digital SLR cameras in terms of sure speed, and is an action photographer's best friend (with the possible exception of a REALLY expensive professional SLR). It has also received rave reviews, and is one of the all-time top rated digital SLR cameras.
So where does this leave the D80? Well, in a fairly strange spot.
If you're absolutely wedded to Nikon as a brand, and want something with more power and capacity than a D50 or D40, then the D80 is certainly a step up. It's also a good choice for anyone who wants a 10 megapixel Nikon for less than $1,000.
However, the price of the D200 keeps dropping (it was released in 2005 while the D80 showed up in 2006), which means that each month the difference in price between these two cameras is reduced. Since that's the case, it's definitely worth your while to take a good close look at the D200 before you run out and get a brand new D80.
Accessory of the Month
Given how much I've been talking and writing about lenses lately, it seemed to make sense that this month's accessory should be related in some fashion to lenses - and so it is.
I feel that must-have accessory for any digital SLR lens is an UltraViolet (UV) filter.
This is a clear glass filter that screws onto the front of your lens. While its stated purpose is to block out UV rays that might affect the quality of your photograph, the real reason to have one of these permanently attached to your lens is that they protect the lens.
UV filters come in different sizes (measured in millimeters) and these measurements match the diameter of different lenses (not all lenses use the same size filter). How do you determine the size you need? Just remove the lens cap from your lens and look at the back. If you see a measurement in millimeters (i.e. 56mm or 72mm) then that is the size of the UV filter you need to get.
The issue here is that if you scratch the glass on the front of your lens, you've permanently damaged the ENTIRE lens. There's no simple way to just swap out the glass on the front of it.
Purists will argue strongly that putting anything between the lens and your subject compromises the quality of the image. I've always believed that these same purists are the ones who can afford to replace a $600 lens if they accidentally scratch it.
I prefer the more practical approach: purchase a $50 UV filter, and - in the off chance that you should drag the front of your lens across a large rock - just go out and buy another filter. While it may have a slight impact on the quality of your photos, the return is significantly larger - peace of mind.
I purchase all of my lens filters from either Amazon or Adorama, due to their great selection and comprehensive return policies.
In ConclusionThe PMA buzz is already building - just today I read about the "upcoming" release of no less than 3 new digital SLR cameras.
If you're on the verge of buying a new digital SLR camera, I urge you to WAIT.
In just one short week the new cameras will be announced, and at that point you can decide whether or not it's worth it to buy a camera now, or to wait for the next greatest model once it's released.
Thanks for reading, and happy picture-taking!
--Chris Roberts, Your Digital SLR Guide
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