Digital Photography from 20,000 Feet
by Wesley Fink on September 25, 2006 12:05 AM EST- Posted in
- Digital Camera
Taking a Picture: Putting it All Together
Now that the basics of how a digital SLR works have been covered, we are ready to put it all together. For those who have had enough of new ideas to remember and balance it should be pointed out that you don't really have to understand or adjust any of this to take images with a digital point-and-shoot or a digital SLR. All the digital SLR cameras on the market are autofocus and auto-exposure, and some even have the very consumer-oriented programs that make decisions for you in tough situations like backlight or sports. However, without understanding a bit about what your automatic camera is doing you will never figure out why that kit zoom takes blurry shots of your family on Christmas morning or your son's birthday party or your daughter's dance recital. With understanding you can make choices to fix these problems.
Why the Kit Lens is a Dog
For some reason, the world has moved to zoom lenses. There is no doubt they are definitely convenient for cropping in the camera, but most people would rather have a sharp picture they can cut in Photoshop instead of a blurred one that is already cropped. You see, people seem to have forgotten the compromises of most zoom lenses. To better understand this let's look at equivalent exposures.
If you followed our discussion of the basics, all of the exposures above represent the same amount of total light. As shutter speed increases (less light) then aperture decreases (more light). The chart below also shows equivalent exposures - we have just shifted the values to a common indoor scene at a moderately "fast" ISO of 400.
As you can clearly see our old normal f1.7 can shoot this between 1/125 and 1/250 - which is plenty fast enough to get a sharp picture with equivalent 75mm f1.7 normal on a digital SLR. A 28mm f2.8 would behave like a 42mm f2.8 normal lens and also be fast enough to shoot at 1/60s. Our kit 18-55mm is equivalent to a 28 to85mm,. At the short end at 1/45 s it is probably fast enough to capture a sharp image, but it gives out quickly and will definitely yield blurred images at anything above about 45mm. At the telephoto end of 85mm (55mm) the shutter speed for the fastest f5.6 is 1/15s - which will definitely be a blurry picture. If you were shooting at ISO200 nothing would be sharp with your kit zoom under these conditions, as everything would shift a notch to the left. At the default ISO 100 the best you could do would be between 1/8 and 1/15s and blurry.
The point is, your kit zoom is for shooting outside and indoors with flash at limited range. It is the wrong tool for available light photography. If you have followed this it is our advise that you buy a normal lens as your first interchangeable lens for your digital SLR. Canon and Nikon still make reasonable 50mm f/1.8 lenses, which also happen to be the sharpest lens in either lens lineup. The bonus on a digital is it becomes a 75mm f1.8 fast short telephoto, which is great for portraits and available light photography. Bonus two is that the close focus is the same but the image is magnified by a 1.5 to 1.6x factor, making the lens a terrific macro lens. Minolta has a great 50mm f1.7, as does Pentax, but used prices have been rising recently. The other option is a 28mm or 35mm lens. There are plenty available at f1.8 to f2.8 on the used market and you get a fast true normal lens of 42mm to 53mm focal length. Since the APS C or DX format only uses the center of the image, the third bonus is that even mediocre lenses with edge falloff in the corners on 35mm are normally very sharp in the area used in digital SLR photography.
There is also a new market developing for fast fixed focal length lenses for the APS C/DX. Several companies have announced new 30mm to 50mm f1.4 to f2.0 lenses for the smaller APS C/DX format. Sony picked up the Minolta 50mm f1.4 for their new lens line, though we wish they had also picked up the excellent and reasonable 50mm f1.7 instead of just the $350 f1.4.
There is also the option of fast zoom lenses, but zoom lenses are rarely if ever as sharp as fixed focus and the prices for fast zooms are high. There are several independent and brand name zooms in the 28-75mm f2.8 format. They range in price from $450 to $5000 or so. Fast, quality zoom lenses cost big money, because they are hard to design and expensive to make. A fixed focus lens gives you that pro quality at a much lower price - particularly if that fast fixed lens is a normal 35mm lens.
Image Stabilization
Image stabilization was first introduced by Nikon and Canon in specialized lenses designed for action photography. These lenses were first designed for pros at pro prices, but they quickly found their way to consumer zoom lenses with wider zoom ranges than kit zooms. The advantage of the image stabilization is that the stabilized zoom lens can produce sharp images at a couple of f-stops slower than the normal rule. That means a 125mm focal length can be handheld with sharp results down to about 1/30s, while a 28mm wide angle can go down to 1/8s or less. The problem with these "image-stabilized" lenses is that they are relatively expensive, starting at $300 or so and going up to thousands of dollars.
More recently, Minolta introduced image stabilization into the SLR camera body. That means any lens mounted on the camera can have the advantage of image stabilization. The Minolta Maxxum 7D was the first interchangeable lens SLR to offer this feature, which was also continued on the mainstream-priced 5D. Sony has continued this feature in their new 10.2 megapixel $899 A100 and improved the effectiveness, they say, to 3 to 3.5 stops. Sony has also licensed the steady shot technology to Pentax, which uses it in their K100D and the announced K10D. It will also appear in future Samsung SLR cameras, since they use the Pentax mount and are basically relabeled Pentax cameras.
Image stabilization, with custom lenses or built into the camera body, allows normal zoom lenses to act like they are faster - some 2 to 3.5 stops faster - and this makes them usable in the difficult situations we described above for zoom lenses. It is a good feature, but keep in mind that the body-integral steady shot also works with any lens, including the fast normal lens. This extends the useful speed of the normal lens even further, just as it does the zoom lens.
One significant advantage of image stabilization with a normal lens is the ability to shoot greater depth of field in available light. Shots that were doable before with shallow depth-of-field, can now be shot with a greater range or depth of sharpness. This is particularly useful for things like we do at AnandTech - shooting motherboards in available light to avoid hot spots, while still keeping the entire board in sharp focus.
Now that the basics of how a digital SLR works have been covered, we are ready to put it all together. For those who have had enough of new ideas to remember and balance it should be pointed out that you don't really have to understand or adjust any of this to take images with a digital point-and-shoot or a digital SLR. All the digital SLR cameras on the market are autofocus and auto-exposure, and some even have the very consumer-oriented programs that make decisions for you in tough situations like backlight or sports. However, without understanding a bit about what your automatic camera is doing you will never figure out why that kit zoom takes blurry shots of your family on Christmas morning or your son's birthday party or your daughter's dance recital. With understanding you can make choices to fix these problems.
Why the Kit Lens is a Dog
For some reason, the world has moved to zoom lenses. There is no doubt they are definitely convenient for cropping in the camera, but most people would rather have a sharp picture they can cut in Photoshop instead of a blurred one that is already cropped. You see, people seem to have forgotten the compromises of most zoom lenses. To better understand this let's look at equivalent exposures.
| Shutter Speed to f/stop Comparison | |||||||||||
| Shutter Speed | 1/4 second | 1/8 | 1/15 | 1/30 | 1/60 | 1/125 | 1/250 | 1/500 | 1/1000 | 1/2000 | 1/4000 |
| f/stop | f/45 | f/32 | f/22 | f/16 | f/11 | f/8 | f/5.6 | f/4 | f/2.8 | f/2 | f/1.4 |
If you followed our discussion of the basics, all of the exposures above represent the same amount of total light. As shutter speed increases (less light) then aperture decreases (more light). The chart below also shows equivalent exposures - we have just shifted the values to a common indoor scene at a moderately "fast" ISO of 400.
| Shutter Speed to f/stop Comparison | ||||||||||||
| Shutter Speed | 1/2 second | 1/4 | 1/8 | 1/15 | 1/30 | 1/60 | 1/125 | 1/250 | 1/500 | 1/1000 | 1/2000 | 1/4000 |
| f/stop | f/16 | f/11 | f/8 | f/5.6 | f/4 | f/2.8 | f/2 | f/1.4 | - | - | - | - |
As you can clearly see our old normal f1.7 can shoot this between 1/125 and 1/250 - which is plenty fast enough to get a sharp picture with equivalent 75mm f1.7 normal on a digital SLR. A 28mm f2.8 would behave like a 42mm f2.8 normal lens and also be fast enough to shoot at 1/60s. Our kit 18-55mm is equivalent to a 28 to85mm,. At the short end at 1/45 s it is probably fast enough to capture a sharp image, but it gives out quickly and will definitely yield blurred images at anything above about 45mm. At the telephoto end of 85mm (55mm) the shutter speed for the fastest f5.6 is 1/15s - which will definitely be a blurry picture. If you were shooting at ISO200 nothing would be sharp with your kit zoom under these conditions, as everything would shift a notch to the left. At the default ISO 100 the best you could do would be between 1/8 and 1/15s and blurry.
The point is, your kit zoom is for shooting outside and indoors with flash at limited range. It is the wrong tool for available light photography. If you have followed this it is our advise that you buy a normal lens as your first interchangeable lens for your digital SLR. Canon and Nikon still make reasonable 50mm f/1.8 lenses, which also happen to be the sharpest lens in either lens lineup. The bonus on a digital is it becomes a 75mm f1.8 fast short telephoto, which is great for portraits and available light photography. Bonus two is that the close focus is the same but the image is magnified by a 1.5 to 1.6x factor, making the lens a terrific macro lens. Minolta has a great 50mm f1.7, as does Pentax, but used prices have been rising recently. The other option is a 28mm or 35mm lens. There are plenty available at f1.8 to f2.8 on the used market and you get a fast true normal lens of 42mm to 53mm focal length. Since the APS C or DX format only uses the center of the image, the third bonus is that even mediocre lenses with edge falloff in the corners on 35mm are normally very sharp in the area used in digital SLR photography.
There is also a new market developing for fast fixed focal length lenses for the APS C/DX. Several companies have announced new 30mm to 50mm f1.4 to f2.0 lenses for the smaller APS C/DX format. Sony picked up the Minolta 50mm f1.4 for their new lens line, though we wish they had also picked up the excellent and reasonable 50mm f1.7 instead of just the $350 f1.4.
There is also the option of fast zoom lenses, but zoom lenses are rarely if ever as sharp as fixed focus and the prices for fast zooms are high. There are several independent and brand name zooms in the 28-75mm f2.8 format. They range in price from $450 to $5000 or so. Fast, quality zoom lenses cost big money, because they are hard to design and expensive to make. A fixed focus lens gives you that pro quality at a much lower price - particularly if that fast fixed lens is a normal 35mm lens.
Image Stabilization
Image stabilization was first introduced by Nikon and Canon in specialized lenses designed for action photography. These lenses were first designed for pros at pro prices, but they quickly found their way to consumer zoom lenses with wider zoom ranges than kit zooms. The advantage of the image stabilization is that the stabilized zoom lens can produce sharp images at a couple of f-stops slower than the normal rule. That means a 125mm focal length can be handheld with sharp results down to about 1/30s, while a 28mm wide angle can go down to 1/8s or less. The problem with these "image-stabilized" lenses is that they are relatively expensive, starting at $300 or so and going up to thousands of dollars.
More recently, Minolta introduced image stabilization into the SLR camera body. That means any lens mounted on the camera can have the advantage of image stabilization. The Minolta Maxxum 7D was the first interchangeable lens SLR to offer this feature, which was also continued on the mainstream-priced 5D. Sony has continued this feature in their new 10.2 megapixel $899 A100 and improved the effectiveness, they say, to 3 to 3.5 stops. Sony has also licensed the steady shot technology to Pentax, which uses it in their K100D and the announced K10D. It will also appear in future Samsung SLR cameras, since they use the Pentax mount and are basically relabeled Pentax cameras.
Image stabilization, with custom lenses or built into the camera body, allows normal zoom lenses to act like they are faster - some 2 to 3.5 stops faster - and this makes them usable in the difficult situations we described above for zoom lenses. It is a good feature, but keep in mind that the body-integral steady shot also works with any lens, including the fast normal lens. This extends the useful speed of the normal lens even further, just as it does the zoom lens.
One significant advantage of image stabilization with a normal lens is the ability to shoot greater depth of field in available light. Shots that were doable before with shallow depth-of-field, can now be shot with a greater range or depth of sharpness. This is particularly useful for things like we do at AnandTech - shooting motherboards in available light to avoid hot spots, while still keeping the entire board in sharp focus.
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squiddy - Thursday, February 15, 2007 - link
I'm fairly versed in film and digital SLRs and have been shooting since the mid-80s. Nikon afficionado here but I did have a few Canon EOS film bodies back in the day. Currently use a D70s and soon hopefully a D200 in my bag.Anyway, as to sugestions for future reviews, the technical aspect tests are all well and good since numbers are always easy to quantify. The MP count, max resolution, test charts and etc do help people choose cameras after all. What I'd like to see more of are subjective reviews. How user-friendly is the camera? Are the menu's easy to navigate and the features easy to get to? How are the ergonomics and will my hand require a chiropractor after a long day of shooting? Is the camera balanced even when using a medium telephoto lens? How about accessories (flash kits, filters, battery grips, flash brackets, etc), are they useful for this camera or just gravy?
What made me write these additional questions is that I experienced it when I borrowed a Canon 350d for a friend's wedding. This was before my Nikon D70s and I absolutely loved/hated it. The pictures were great but required heavy menu navigation for white balance and iso settings. The camera was lighter than my old film Nikon so it wasn't tiring to carry all the time but the grip was awful. My pinky was sticking out under the body and a;; the weight was focused on the upper/rear quarter of my right palm. I'll tell you now, it hurts to use it for a long time. Especially with a 430ex flash. I then tried a friend's D50 and a D70 after that and it solidified my Nikon preference. Great ergonomics and the two dials give you much greater flexibility on the fly.
These reviews are probably aspects that the average consumer won't consider before purchasing and just focus on numbers but it greatly affects the usability of the camera in the long run.
Thanks guys and keep up the great work!
appu - Sunday, October 8, 2006 - link
I don't know if these have already been covered in the comments earlier. There are quite a few and I didn't read them all.1.) When talking about vibration reduction, you need to make sure you tell your readers that VR/IS *cannot* eliminate subject motion blur. It can only eliminate (to a degree) blur caused by handshake. I'm surprised you missed such an important point considering that you felt most AT readers are newbies at photography. It's all dandy to believe that VR gets you sharp images all the time. No, it doesn't. There are caveats and you might have mentioned them.
2.) The real benefit of SLR cameras is - more than anything else - the fact that the photographer sees what the lens sees. That's a major, major advantage of a SLR over point-and-shoots and rangefinders which exhibit parallax error by the nature of their design, especially if the subject is close to the lens/camera. Given this, you might have also mentioned that sensor-based stabilization techniques are a bit of a misfit (atleast that's what I tend to think) because having a stabilized sensor still *will not* give you a stabilized image in the viewfinder. However, lenses which have VR in-built *will* give you a stabilized image in your viewfinder - again going back to the "what you see is what you get" thing. Having stabilized sensors is good for the customers as they don't pay VR royalty on every lens they buy, but I don't see the point in seeing a shaky image in the viewfinder and somehow expecting something sharp (to what degree I may not know) in the final image. Maybe 99.9999% here (or anywhere) wouldn't agree with me on this point but I think it's worth a note.
3.) Not all kit lenses are dogs. The 18-70 DX I have for my Nikon D70 is a wonderfully sharp, contrasty lens (of course in available light situations) and after almost 2 years of shooting DSLRs I can safely admit that I've not "outgrown" this lens. It still manages to surprise me every once in a while and I don't see the need for an exotic f/2.8 zoom in this range as yet. Point I'm trying to make is - don't berate kit lenses. They are there for a reason, and as with any lens, there are certain advantages and certain disadvantages. As a photographer, it's important to understand what every bit of your equipment is good at and then maximize the technical potential of your images because of this understanding. Infact, building up on this point...
4.) I'll go so far as to say that, even with fixed focal length (prime) lenses, the so-called "sweet spot" in terms of image sharpness and contrast is usually achieved when the lens is stopped down by 1.5 to 2 stops from its maximum aperture. If you are always going to think in terms of how zoom lenses are "bad quality" compared to primes, I'd encourage you to start shooting 2 stops down on your primes (and thus lose all the speed advantage these primes offer). I think you get what I'm trying to say. Let's not get too hung up on trivialities like this because, and I repeat because, modern zooms, even the consumer zooms produce wonderful images in the hands of capable photographers. And then you have pro-grade zooms like the 70-200 f/2.8 VR from Nikon and Canon's 17-40 f/4L etc. Yes, they are costly, but so is a 300 f/2.8 VR Nikkor or a pro-grade ~100mm macro. The price differential is evident only when you start looking at wide-to-medium-tele or super-wide-to-normal fast zooms (28-70 f/2.8, 17-55 f/2.8) and even then the output from these lenses is well worth their cost and the walk-around convenience they present to photographers who prefer this range of focal lengths. So, not all zooms are "bad". Things have improved, just as they continuously do in the computer hardware business. Let's not get stuck in old notions based on old equipment manufactured using old processes.
Keep up the nice work!
appu - Sunday, October 8, 2006 - link
Ok, one last point -5.) In your second last page, you talk about "lens confusion" and how you'd like the industry to move to a standard naming of lenses. I don't understand what can be more standard than the focal length itself - a very physical property of a lens. A 35mm lens has a focal length of 35mm. Period. It doesn't depend on what format camera it's bolted on to. A 35mm lens is 35mm whether it's used on a 4x5 view camera or a 645 medium camera or a 35mm film camera or a digital equipped with an APS-C or.... you get the picture. In itself, the naming of the lens by its focal length (range, with zooms) is *not* confusing. What's confusing is what people make it out to be - quoting effective focal lengths for formats all and sundry, where as in reality, the measure everyone needs to be worried about is field-of-view. A 35mm lens will have different fields-of-view when used with different camera formats.
We don't need a standard for identifying lenses. We already have one - focal length (a physical property that doesn't change) and field-of-view (a very measurable metric). If anything, it's the "effective focal length" paradigm has to be done away with, IMHO.
appu - Sunday, October 8, 2006 - link
In the last line of the third from last paragraph - Nikon doesn't make a 11-18mm as far as I know. They do have a 12-24 f/4 DX and Sigma also has a 12-24 (I think a non-constant aperture) which can be used on full-frame cameras too, unlike the Nikon 12-24 DX. The 11-18mm is made by one (or both) of Tamron and Tokina I think.directed - Wednesday, September 27, 2006 - link
When reviewing DSLRs, I want to know how quickly they can autofocus in different lighting conditions. I want to know how good the autoexposure is in different situations. I want to know how the different flashes perform in different settings (not just the built in ones, but the ones you can buy for them). I want to know how accurate the color reproduction and contrast is. I want to know how good the jpg compression is (lets face it, few people will be using RAW). I want to know how long the batteries will last in different situations. I would also like there to be a comparison with other models in a similar price range as well as a comparison with the cheaper and more expensive models of the same manufacturer.Boy, looking at my post I sound demanding. LOL, I'm sure Anandtech is up to the challenge.
yyrkoon - Wednesday, November 1, 2006 - link
I dont know, I dont use AF for demanding lighting situations, I use the infinite Focus setting, and set the rest manually. That, and I think all 'prosumer' DSLRs have a fairly 'shitty' on cam flash, and alot of us would probably be more concerned with the hotshoe 'adapter'However, I will agree with battery life as an important factor, but to be honest I'm personally more concerned with how fast the camera is (FPS), and the media type used.
I see alot of stuff on dpreview.com like 'default <insert something relivent> setting is BAD' etc, but most of the these cameras can be manually adjusted away from default settings, so, IMHO, it's a moot point, and is pointless to really mention, learn how to use your camera ;)
You're not demanding, you just know what you want :)
yyrkoon - Wednesday, September 27, 2006 - link
Forget what all the nay sayers are saying guys, write you articles. I've been interrested in the Sony A100 for several months now, since the preview on dpreview.com. I also think you're right concerning the *mass* of information that dpreview gives off for thier camera reviews, most of it is un nessisary for all but the professionals, most of us just want to know things like, how many FPS does the camera achieve, how does it handle low light situations, how clean are the photos, etc.Carry on :)
silver - Wednesday, September 27, 2006 - link
Another good point. AT has always been about presenting good, practical information on the products that we use and in this context has always done a great job.The A100 certainly has my intrest as well but do note that most pro's do not need bells and whistles in their equipment. In fact most don't even want them available as it adds to both cost and complexity with almost no practical return in value.
Lord Midas - Wednesday, September 27, 2006 - link
Very good article Wesley. Thanks.Still a lot of this is still baffling at the moment but that should change when I get my Canon Rebel XTi 400D for Christmas.
What I would like to see in the reviews would also include the quality of the bundled lens (the Canon comes with the 18-55mm lens). As well as with a quality lens.
Will you also include reviews of lens:
For example you do the "Mid Range GPU Roundup - Summer 2006"
So you could do this with Normal, telephoto, etc lens.
So instead of reviewing one lens you can do a group test.
And I also think that a few standard photos for all the reviews would be good (indoor, outdoor, macro, etc) and a few random ones the the reviewer would think we would like.
Keep up the good work. Thanks.
mesonw - Tuesday, September 26, 2006 - link
Just wanted to add my 2p-worth. I feel I fit fairly well into the target audience you're aiming at. I'm very lacking when it comes to the technical details of cameras, digital or otherwise, yet I have a great desire to take good and interesting pictures.It's good for people to offer tips and ideas for your upcoming articles, but I don't see the point of the very knowledgeable and camera-savvy crowd out there making harsh criticisms simply because you're targetting people with less knowledge than them. Like they say, there are other sites to get in-depth information if they want it, so why berate AT for catering for others?
I for one look forward to your articles on the subject, because I know they will be well written, provide useful information and insights, and very likely make me a better amateur photographer.
Good work AT.