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Understanding RAW vs. JPEG File Types (Video Tutorial)

One of the advantages of your DSLR camera is its ability to shoot in multiple file types, such as JPEG and RAW. This video tutorial will demonstrate the differences and show you the benefits of...

Camera Lens

by Philip Greenspun, June 1999 (updated January 2007)

Bodie, California.

Once you've settled on the subject and the light, you have to decide on the relative prominence of objects in the scene. By moving the camera position back and forth, you can adjust the relative size of objects in the scene. After you're happy with the position, you pick a camera lens whose angle of view encompasses all the objects that you want to include in the photo.

Objects? Relative prominence? I only want to take a picture of my friend Cyrano! There is only one object in the scene and it is Cyrano's head.

Au contraire! The objects in this scene are Cyrano's nose, Cyrano's ears, and Cyrano's eyes. Suppose that you position your camera 10" from Cyrano's eyes. If his nose sticks out 5" in front of his eyes, then it will be only half the distance from the camera as the eyes and therefore relatively more prominent. Stretch out your arm right now and compare the size of your index finger to the lines of text on the monitor. Only about as big as a paragraph, right? Now close your left eye and bring that same finger in until it is just in front of your nose. Note that your finger appears taller than the entire monitor.

Aesthetic tip from MIT: when your nose sticks out 5" in front of your eyes, you don't want it to appear relatively more prominent.

Suppose that you actually want this photo as the "before" illustration in a plastic surgeon's advertisement. Well, then haul out the 24mm wide angle lens and you can have a complete portrait taken from 10" away.

Suppose that you wish to flatter Cyrano. You'll want to back up until you are separated by the length of a football field. Now his nose is still 5" closer to the camera but that is 5" out of 100 yards (note for European readers: 100 yards is just short of half a standard furlong.) So instead of being 50% of the distance to the camera as Cyrano's eyes, the nose is 99.86% of the distance away. It will not be significantly more prominent.

What about the 24mm lens from this camera position? It will give you a nice photo of the entire stadium and the city behind it. Cyrano's face will appear as a portion of a grain of silver on the film. You're now 100 yards away from Cyrano so you will need the Mother of All Telephoto Camera Lenses. In fact, according to the formulas in my Kodak Professional Photoguide, if Cyrano's face is 12" high, you will need a 7500mm lens to fill the frame with it. Cyrano will be flattered but considering that a Canon 600mm lens costs almost $10,000, the effect on your wallet will not be a happy one.

Exactly how long a camera lens do you need?

How far away is your subject? (in feet)

How high is the object you want to fill the frame? (in feet)

Kid and Telescopes.  Monterey, California.

Apologies to people from countries that have adopted sensible units.

If sensors and camera lenses were perfect... you would need only one lens!

In a perfect world, you would leave the house with only a Canon 14 super-wide lens. You would worry only about camera position, secure in the knowledge that the 14mm lens was wide enough to capture the entire subject under 99% of conditions. Then if you wanted a picture of just a friend in the middle of the frame, you'd crop down to just the center and use that. The result would be the same as if you'd used a 100mm portrait lens.

The reason this doesn't work is that lenses and sensors aren't perfect. If you throw away 98% of the area of the digital sensor (and/or make a huge enlargement), you can expect to have some pretty crummy looking pixels. So if you're sure at exposure time that you will want more magnification, it is best to carry some higher magnification camera lenses.

The rest of this article discusses what kinds of camera lenses we might want to lug around.

Wide angle camera lenses

With a full-frame digital SLR or 35mm film, a wide angle lens is generally considered anything with a focal length of 35mm or less.

Here are a couple of snapshots taken with an ancient Canon 20-35/2.8L zoom lens (replaced by Canon EF 16-35mm f/2.8L II USM, (buy from Amazon)). Note that the image on the left, at 20, appears to be significantly distorted if you view it from far away. But try clicking on it so that you get a monitor-filling JPEG. Then move your face in close to the monitor so that you are viewing it from a few inches away. The distortion disappears, right? A wide angle lens does not distort perspective but, if the viewer of the ultimate image does not adjust his viewing position, it appears to do so.

Porsche and corn.  Pennsylvania. Porsche and corn.  Pennsylvania.
at 20
(camera closer to car)
at 35
(camera farther from car)

As a practical matter, most people these days aren't impressed by a wide-angle effect until you get down to 24mm. Wide angle camera lenses start to get expensive at 20mm ($500) and wider. So good compromises these days are are probably a fixed 24 ($250) or a high-quality 16-35 zoom ($1500). See the Canon and Nikon system pages for an idea of what's available.

Normal Lenses

Eric Jordan, brilliant young computer scientist.  545 Technology Square, 4th floor

A "normal" or "standard" camera lens is one that produces prints with no apparent wide angle or telephoto distortion. In other words, when viewed at a standard distance, a print taken with a normal lens will appear to have no unusual perspective. For a camera taking 35mm film, a 50mm lens is considered normal.

Normal lenses are easy and cheap to fabricate. A 50/1.8 costs under $100 and will optically outperform most of the lenses in any manufacturer's line. Furthermore, normal camera lenses allow photography in rather low light with no flash or tripod. A yuppie with a mid-range zoom lens has a maximum aperture of f/4. A photographer with a 50/1.8 not only saves $200 but is gathering 4 times as much light (2 f-stops). With a standard single-lens reflex (SLR; viewing through the lens), this makes viewing and composition easier because the viewfinder is 4 times brighter.

If you don't feel like saving $200, you can get a 50/1.4 which will gather another factor of 2 in light. If you are a real wastrel, you can splurge $2500 on a lens like the discontinued Canon 50/1.0. This gathers 16 times as much light as a typical mid-range zoom.

Another common option is the 50mm macro lens. I refer you to my article on macro photography and my review of the Nikon 60/2.8 AF lens.

Dublin, Ireland. Carlingford, Ireland.
Japanese Garden. Powerscourt. South of Dublin, Ireland. Temple Bar. Dublin, Ireland. Overturned Golf.  Entering the Wicklow Mountains south of Dublin, Ireland. Newgrange.  Passage Grave built around 3200 BC.  North of Dublin, Ireland.

Telephoto Camera Lenses

100th Anniversary Boston Marathon (1996).

Telephoto lenses are high-magnification devices. These are for when you are photographing something from far away either because you want to flatten perspective or because you are unable to approach your subject.

It is difficult and expensive to produce a high-quality telephoto lens. In fact, only in the last couple of decades have manufacturers been able to design really high quality 300mm and longer camera lenses.

Telephoto lenses can be useful for portraits, most often in the 85-180mm range. Photography of large animals is facilitated by 300-600mm lenses. Photography of birds starts with a 600mm lens and goes up from there.

Telephoto camera lenses that serious Canon EOS photographers buy include the following: 100th Anniversary Boston Marathon (1996).

For the equivalents in the Nikon system, please see our Nikon System Explained page.


A teleconverter is a small lightweight intermediate optic that will increase the magnification of a lens, while reducing its effective aperture. So a 2X teleconverter turns a 300/2.8 into a 600/5.6. A lot of times new photographers ask me if they can save money by buying a teleconverter and sticking it onto their 28-70 zoom to get a 140mm lens. Sadly, good teleconverters cost $400 or $500 and they only work optically on expensive lenses. With a typical zoom lens, you'll get vignetting (darkening of the corners) when using a teleconverter.

Teleconverters are for professionals who own expensive lenses and want to save weight by not carrying two lenses. They are also useful sometimes with specialized tilt-shift lenses so that you don't have to buy these in lots of different focal lengths.

Zoom lenses

Why carry around a whole bag of fixed focal length ("prime") lenses when you could just buy a Tamron 28-300 zoom lens for less than $400? With a twist of a ring, the Tamron will give you any focal length from 28mm to 300mm. The only problem with this idea is that, sadly, the laws of physics and common sense have not been repealed.

Photographic lenses in general are not very good. They only appear to be good because people very seldom enlarge or closely inspect images. Camera lenses are subject to many kinds of distortion, all of which are more difficult to reduce in a zoom lens design. Furthermore, zoom lenses tend to be slower (admit less light) than prime lenses. This forces the photographer into using flash and/or a tripod.

Does that mean you shouldn't buy a zoom lens? Absolutely not. The average Canon EOS photographer will own three beautiful zoom lenses: Canon EF 16-35mm f/2.8L II USM, Canon EF 24-70mm f/2.8L USM (review), Canon EF 70-200mm f/2.8L IS USM (review). These are a great convenience for the lazy and/or pressed-for-time photographer. However, none of these are as good as prime lenses in their focal length range. Each of these zooms costs over $1000, so they won't help you out if you don't like the prices of the prime lenses.

If you can only have one lens, the Canon EF 24-70mm f/2.8L USM is probably better than the Canon EF 50mm f/1.8 II, (buy from Amazon) (review). But the 50/1.8 is better than cheaper mid-range zooms.

Weird Camera Lens #1: The Fisheye

See our review of the Canon 15mm fisheye lens.

Weird Camera Lens #2: The Beyond 1:1 Macro lens

As far as I know, Canon is the only company in the world that makes a lens intended for convenient photography of objects smaller than the film or digital sensor. See the photo.net review of the Canon MP-E 65mm 1X-5X macro lens.

Be Careful (and rich)

Modern digital cameras produce extremely high quality images. In reasonable lighting conditions, the limiting factor in the quality of your image will almost always be the lens. If you want to achieve a good result, you must have the correct lens for the job and it must be a high quality example of that kind of lens.

Lots of companies make high-quality lenses. Sadly, none of them have figured out how to break physical laws and do so cheaply. So if your creative goals require a long telephoto or very wide angle lens, prepare to cough up the big bucks. If you are using a larger format than 35mm, prepare to cough up the big bucks for any lens!


If you own a Canon or Nikon digital SLR, a Hasselblad medium format camera, or any large format camera, you can rent a wide variety of lenses in most major cities. It will definitely expand your creative horizons without breaking you financially. Remember when using a large or medium format camera that a given lens focal length will result in a different perspective than on a 35mm camera. Use this table to convert.


Next: Film.

Readers' Comments

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David Merfeld , December 13, 2001; 06:42 P.M.

Phil has given a very nice summary of options, with one exception. No doubt humility motivated him to omit the best resource for obtaining that perfect lens: used equipment listed in Photo.net classifieds.

Unlike ebay or other general auction sites, we users of photo.net feel comfortable that most sellers of equipment are other serious, or at least honest, photographers. Consider how much faith is required to hand over thousands of dollars to a total stranger, based on his or her assertion that the equipment is both on its way, and in working order.

Over the years, I have purchased many cameras and lenses from photo.net, and have been very pleased with the process. For the non-rich among us, it's a great way to eat AND take pictures.

tOM Trottier , May 29, 2002; 02:34 A.M.

Phil, you say "As far as I know, Canon is the only company in the world that makes a lens intended for convenient photography of objects smaller than a 35mm frame. See the photo.net review of the Canon MP-E 65mm 1X-5X macro lens." Well, you're wrong. Olympus makes several 20mm and 38mm macro lenses. You can put them on bellows and a focusing stage for control and cover from 1.8x to 12.4x. But for convenience, you can also put them on the telescopic auto tube (65-116mm). Then the 38mm covers 1:2.5-4x and the 20mm covers 1:5.8x to 8.3x. Handholdable? Well, I'd use an electronic flash to keep things still and blast enough light to get thru such an extension (even if one of the 20's is f/2).

And the auto tube can be used to extend the close-up focusing of any Olympus or 3rd party lens, from 16mm to 1000mm. For example, the 50/2 (or 50/3.5) macro would focus down to about 1:4x But the shorter macro lenses are better corrected for their macro ratios.


Peter Langfelder , June 07, 2002; 02:02 A.M.

A crop of the center of a frame taken with a 14 mm lens may have the same field of view as a 100 mm portrait lens, but will have a very different (larger) depth of field and presumably a different rendering of out of focus area. Thus a 100 mm portrait lens would be useful even in a world of perfect lenses and film.

David Barts , February 04, 2003; 09:57 P.M.

Another common option is the 50mm macro lens.

Two things to be aware of are (a) macro lenses aren't as fast as non-macro normal lenses, and (b) because so much of the focus ring is taken up to focus at macro distances, there's not much rotation left to focus at non-macro distances. As an example, my Sigma 50:2.8 EX macro lens has a whopping half a centimeter between its 5 foot setting and its infinity setting. That makes accurate manual focusing a very touchy matter at those distances.

I've recently bought a good cheap used 50:1.7 normal lens for the above two reasons.

Michael Hohner , July 19, 2003; 05:33 A.M.

Minolta had a 1x-3x macro zoom for their AF mount for over a decade before Canon made their macro zoom.

john defreitas , October 17, 2006; 01:51 P.M.

Can anyone help me to find the best possible lens for soccer action shooting from the stands with a Sony A-100 for the $200-$500 range? I thought of Sony 75-300mm and Sigma 70-300mm APO Macro. Photos will be taken during the day and evening as well with stadium lights. Thanks. John

Andrew Greeley , January 05, 2008; 10:53 P.M.

Hi there and thank you for taking the time to read and help me out. I have a painful dilemma with respect to the lens I should get. I do not want to sacrifice quality over money but I do not want to buy an expensive lens if it is just a tad better than a much cheaper one. With that in mind what would you rather get between the following lenses (all CANON):

EF 16-35mm f/2.8 L II USM; EF 17-40mm f/4 L USM; EF 24-70mm f/2.8 L USM;

Obviously 16-35mm would be the standard from which I am deviating. Any other better alternative I missed? Any thoughts about SIGMA? Any help is much appreciated. Thank you.

David Bowens , January 23, 2008; 10:48 A.M.

Very poor article full of baseless opinion and useless facts. You make several points, but don't go to much into any detail to explain these points.

If you're going to write a 'textbook' article, then use facts and start from the basics instead of blathering on endlessly about why yuppies use expensive zoom lenses, while later stating that the average EOS photographer uses expensive zoom lenses.

Incredibly poor article, I think i'll find my "textbook" information somewhere else.

kayse Ericksen , February 11, 2008; 11:40 P.M.

I have a lens question. I have a 62mm vivitar, a 50mm canon, and a 35-70 mm canon. I used them back in school when I first started photography with an old canon camera. I now want to get back photography with a digital body. Would these fit a new canon body?

Vaydehi Khandelwal , August 16, 2008; 11:31 A.M.

is a 28-135mm lens good enough to shoot a room??

Andrew Prokos , February 07, 2009; 10:50 A.M.

A 28mm lens is usually not wide enough to shoot a room...I would say 24mm and wider is better. Keep in mind the conversion factor between full frame sensors and smaller sensors like Nikon's DX format. A 17mm lens on a DX camera becomes around 22mm I believe.

Phyliss Crowe , July 17, 2009; 12:57 A.M.

Why did the author whole cloth snub Pentax? Minolta? Olympus? Leica? Yada, yada.

For that matter, why bring brand names into this piece at all? You "might" have been more convincing if you'd just stuck to LENSES, period. You know; like your article title alludes to.

Roy Evans , December 30, 2009; 11:36 P.M.

More a question than a comment. I want to buy a EF 100-400mm f/4.5-5.6 L IS USM Lens for my Canon Digital Rebel XT. Should I get good results with this combination?

Benjamin Michaelis , August 02, 2010; 10:32 A.M.

Good writing. 

MAINAK GHOSH , March 28, 2013; 09:46 A.M.

does a zoom lens of 18-250mm in a DSLR has greater zooming power than any digital camera with 30x optical zoom?

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