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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wheel - Tuesday, September 26, 2006 - link
Thanks for your reply.Regarding the Canon 50mm 1.8, I think most people would agree that the 1.4 is better since it has full time manual focus and also a silent USM motor, plus 8 aperture blades instead of 5 for nicer, smoother looking bokeh (out of focus areas in an image). Of course when you consider the cost differential most people choose the f1.8 and for many it is the smarter choice! However I still believe your sentence in the article suggesting that it happens to be the sharpest lens in the lineup a little misleading. Not a big deal I guess.
If I can make some comments on the following paragraph:
There are plenty of Digital Camera Review sites out on the web, so you may ask why AnandTech is re-launching a Digital Photography section. It appears that current sites are rarely on target with what computer enthusiasts want to know about digital cameras. Some sites make the assumption that the reader knows a lot more about photography than our average reader, which often leads to much of the review being gibberish to a non-photographer. Other sites dwell on tests of things like "start-up times" that were important in early digital, but have become all but meaningless in today's digital SLR market. Still other sites, which are very well-grounded in traditional photography show an obvious lack of knowledge about computers and computer tools that make digital photography so flexible today. It is our sincere belief that we can do it in a better way for our readers and computer enthusiasts everywhere, but please help us as we try to reinvent this wheel. Some of our readers may not like AT delving into Digital Camera Reviews, and to them we say you just can't ignore digital photography any more. Today's digital imaging is nothing more than an optic stuck on a computer, and there is very little left of the mechanical gems that once ruled the world of photography.
A few points:
"Some sites make the assumption that the reader knows a lot more about photography than our average reader, which often leads to much of the review being gibberish to a non-photographer."
So a 'non-photographer' will find a technical review on the big digital camera sites gibberish? I don't think that is a problem, because such reviews aren't really aimed at non-photographers. I would guess that non-computer users are going to find articles on Anandtech about ram timings difficult to understand too!
Other sites dwell on tests of things like "start-up times" that were important in early digital, but have become all but meaningless in today's digital SLR market.
See my comments re: sports / action photography in my previous post. Start up times, shot to shot times and file flush times are quite important to me! Other sites have (very comprehensive) standardised tests that include these timings. I wouldn't say they dwell on the subject though, unless a particular camera is unusually bad at it. If it is not something that is relevant then a reader can easily skip it.
Still other sites, which are very well-grounded in traditional photography show an obvious lack of knowledge about computers and computer tools that make digital photography so flexible today.
In my years of reading the major photo review websites, I haven't encountered this. Without asking you to be specific, can you mention general examples of what you mean?
Cheers,
Ian
tagej - Tuesday, September 26, 2006 - link
The reality is that most computer geeks (myself included) are not photography experts, but are overall tech-savy and interested in things like digital SLR cameras.Sure, I can go to sites like dpreview and the like, and they do an excellent job of reviewing cameras from a pro or prosumer perspective. I could sit and read a bunch of stuff on those sites and educate myself to the point of becoming very knowledgable about cameras... Most of us don't want to do that, or we would have already done so. Instead, AT hit it right on the head with this article, it's a look at digital photograhpy for the tech savy who are not photography experts.
arswihart - Tuesday, September 26, 2006 - link
I totally agree with "wheel." If you feel the need to review cameras, go ahead, but thats not what I come to Anandtech for.aeternitas - Monday, September 25, 2006 - link
" The artistic types distrust turning their vision into cheap Adobe Photoshop tricks, and the tech-savvy are so enamored of technology and editing that they often don't have a clue about what makes a good photograph and what lens to use in a given situation. "I stopped reading there. If you want respectable people to respect you, its a good idea not to be a fucking jackass and insult the readers in the second paragraph. Get some common sence.
Resh - Tuesday, September 26, 2006 - link
Have to side with Wes on this one. Nothing in his words are offensive. He is simply stating the view point of two extremes of the population who both hold very valid positions.Wesley Fink - Monday, September 25, 2006 - link
These are comments from discussions I have had on Forums and in emails with readers. They were not meant to offend, but to point out the fact that the art and technical don't always mix well. This is particularly true when the market, and not the people affected, is forcing changes in the way people work.ksherman - Monday, September 25, 2006 - link
since we have had a camera review on AT! Kudos!To those that say no, I also like to read reviews from multiple sources. AT- dont try to be dpreview, make your reviews a little less technical, easier to understand. Not to fault them, but you need to have some pretty serious photography knolwedge to get their reviews. I would welcome an easier to understand set of reviews. (I do still enjoy reading about my level :-))
On another note, on the last page, you called canons new camera the Rebel XT1, its actually the XTi.
Also, take a gander at the Panasonic Lumix DMC-FZ50, its a sort of pre-digital SLR camera. It basically is a digital SLR, but with an attached lense. Its looking to be my next camera purchase since I am too poor to afford the "real" DSLRs.
saiku - Monday, September 25, 2006 - link
I am a hobbyist photographer (Canon 350D) who likes to do macros/scenery when I can. What I'd love to see are guides for people who want to get into DSLRs and don't know which camera system to buy into. For example, if a person is interested in macros, should he buy into a Nikon system? What about the guy who wants to shoot lots of indoor shots of his baby? Lens choices are very tough for newbies to make and a hefty dose of attention to what lens to pick would be great.PokerGuy - Monday, September 25, 2006 - link
Wes, thanks for the great article. I'm a grizzled vet when it comes to PC tech, but when it comes to photography I'm pretty much a noob. I appreciate the article and look forward to reviews, especially since I'm about to purchase my first digital SLR camera.One dumb question: are lenses for SLR cameras "standard" in terms of connecting to the camera body? ie, can I take a Canon EOS Rebel 2000 SLR lens and hook it up to some other digital SLR camera?
Resh - Monday, September 25, 2006 - link
Also, Canon EF-S lenses only fit certain cameras (Digital Rebels, 20D, 30D), but EF lenses work on all current Canon bodies, digital or film.Third party manufacturers like Tamron and Sigma will make lenses for both Canon and Nikon.