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09/05/2005 06:40:29 AM · #1 |
A simple question for those who know the answer...
Being new to DSLR's and hoping to get a 350D in a month or two, I have started looking at the different lenses that are about, but I don't understand the terminology very well.
Example - Canon EF 75-300mm 75-300 f/4-5.6
The mm measurement, in this case 75 to 300mm - what does this mean? Is it, the higher the number, the greater the zoom?
Also, the aperture ratings, in this case f/4-5.6. Is this a minimum or maximum aperture setting that can be used with the lens? I assume on auto mode, the camera will know this anyway, but if on manual, should the aperture be set within this region, or doesn't it matter?!?!?!?
Example 2 - Canon EOS EF 35-350mm f/3.5-5.6 L USM
With this one, what does USM mean?
Does anyone know of a website or forum post where all this is explained for noobies!
Thanks,
AL.
Message edited by author 2005-09-05 06:41:53. |
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09/05/2005 06:47:16 AM · #2 |
You got that right about MM, the greater the number the bigger the magnification and the smaller the number the wider the lens.
The aperture ratings are just for maximum aperture. The 4-5.6 means that at the widest setting, 75mm it has a maximum aperture of f4 and at 300mm it´s got a maximum aperture of 5.6, so the aperture range is probably 4-22 at 75mm and 5.6-32 at 300mm, I am not sure, I have never used the 75-300 lens.
USM means ultra sonic motor, just means that it´s quiet, no buzzing sound when it´s focusing and usually means that it´s quicker too.
Here is some info from Canon about their DSLR lineup -> //consumer.usa.canon.com/ir/controller?act=ProductCatIndexAct&fcategoryid=111
Message edited by author 2005-09-05 06:48:23. |
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09/05/2005 06:55:58 AM · #3 |
Great stuff - thanks for that!
I'm looking through EBAY at the different bits of kit and the prices they are gping for and I am surprised that lenses with similar specifications seem to be priced at completely different ends of the market!
For example:
Canon EOS EF 80-200mm II AF lens - currently at just £41
Canon 70-200mm f2.8 IS L - at £680
Perhaps this a bad example 'cos of the image stabalisation bit?!?!?
AL. |
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09/05/2005 07:01:32 AM · #4 |
hear is a good basic learning resource from canon
//www.photoworkshop.com/canon/index.html
click on the rebel xt lessons
you might have to resize the new window to see the links at the bottom to all the lessons including lessons on lenses (lesson 2 under basics)
hope this helps
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09/05/2005 07:12:35 AM · #5 |
If you see "L" in the lens description, it is Canon's professional range. Faster electronics (faster autofocus), better build quality, better glass, weather proofed, and generally white or grey with a red ring around the front. Very nice equipment!
In the middle, there are semi pro lenses, which will have decent build quality (meaning metal mounts, manual override of focus, focus range on lens) and reasonable glass. Sometimes have a gold ring around the front.
At the bottom are the budget lenses, with plastic mounts, sometimes have DC motors instead of USM (DC motors are slower and more audible), cheaper glass.
The better the glass, the wider open the apertures it will tend to give you at various focal lengths. As the zoom gets bigger, this normally requires more glass. Hence (from your example) Canon 70-200mm f2.8 IS L - at £680 allows you to use f2.8 to 200mm. It has a very large bit of glass at the front to enable that (diameter of 77mm), and it weighs quite a lot. The Canon EF 75-300mm 75-300 f/4-5.6 will allow you only f/5.6 at 300mm (and about f4.5 at 200mm) - it cannot open up as wide. One reason for this is its size (it has a lens diameter of 58mm). It is much lighter and comparatively smaller than the 70-200mm f2.8 IS L.
The IS versions of lenses are slightly more expensive than the non-IS versions.
The flexibility and speed of "L" lenses is very desirable, and they afford a slightly sharper image quality due to better glass. However the trade off is a bigger camera bag and the money. I think that people tend to buy as good a quality as they can afford.
Do not worry about having to remember any of this when the lens is on your camera - the camera will sort it out for you, if you want it to.
Message edited by author 2005-09-05 07:13:25. |
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09/05/2005 08:24:04 AM · #6 |
Thanks for that guys. Has cleared it up a little for me!
I'll have to look at the lessons link at home as work PC won't allow me to install various bits needed for the site!
Cheers,
AL |
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09/05/2005 10:32:42 AM · #7 |
As a rough guide to lens qualities you could have a look at this site:
Photodo
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09/05/2005 11:20:45 AM · #8 |
You mentioned using the Auto mode. You should be aware that most higher up cameras, 350XT included, have the ability to choose a number of different combinations even within the auto settings.
For example, if your auto mode picks out a shot at 1/125th at f/2.8, rolling the little wheel will allow you to halve the aperture (dropping by one stop) and double the exposure time to 1/60. There are usually 4-5 different options within any particular shot.
This allows you to take drastically different pictures of the same subject. Things such as Depth of Field and motion blur (desired and non) as well as apparent noise change drastically with just a few clicks of the wheel.
Why is this relevant to lens choice? Two reasons:
Lenses that cannot open to wider apertures will be more limited in the types of shots they can take (a 70-300 f4.0-5.6 will only be able to open to f5.6 at full telephoto, which might make it significantly harder to stop motion of a bird in flight or hold the camera still enough to get a sharp picture compared to a lens that is close to that in zoom range, but can open the aperture to f4.0 or 2.8). Real limitations include light, stable shooting platform, available light, photographers personal abilities and whatever else might be happening at the time. You can only shoot as good as the weakest link in the chain. Luck picks up the rest of the slack.
Lenses with a constant aperture are able to zoom in and out without losing focus. If you frame a shot and set focus, but want to zoom in on a subject, you may do this without refocusing. This is why some lenses are listed like 70-300mm F4.0-5.6 and others are listed as 70-200 f2.8. How important this is to you makes a big difference to your wallet.
More light means better performance in the focusing accuracy and speed. You can't always turn on an extra light. If a lens is able to gather more light, it has a similar effect. A 50mm f1.8 prime lens will allow the camera to focus and perform better than an 18-55mm f3.5-5.6 pretty much most of the time. You will also be able to take brighter pictures with less light. Some cameras (20D and better) even have special autofocus modes when attached to lenses that are f2.8 or better. For various reasons, many people feel that a wider aperture by two stops is better than IS because it allows you to stop motion in front of the lens instead of only behind it.
Finally, if you would like a couple of recommendations from a guy who doesn't really have authority to speak, but has been doing a fair bit of research lately and has narrowed down a lot of recommendations from really slick shooters here and elsewhere, I would say for whatever style of shooting you do, it might be good to check out these lenses:
Canon 50mm f1.8 $70 (bonus - cheap prime has stellar performance! and has powerful macro abilities with the reverse thread mount)
Tamron 28-75 f2.8 $360 (XR is the equivalent of Canon's L series. Nearly as good according to many)
Sigma 70-300mm f4.0-5.6 DG (only get the new one with DG) $220
or if you have the money,
Canon 70-200mm f2.8L $1100 plus a
Canon 1.4x Teleconverter $279
Pick your lenses carefully. Know before you buy. I'm still 6 months away from buying and I'm still reading around 2-3 hours a day on lenses.
Hope it helps.
Message edited by author 2005-09-05 12:34:40. |
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09/05/2005 12:04:28 PM · #9 |
Basically, you cannot and will not go wrong with the L class of lenses. Pricey yes, but you'll have them forever! My first two were the 24-70 and 70-200 L lenses. I then added a Sigma 105 macro and the 17-85 all-purpose walk-around lens. Still dreaming of the 100-400! LOL
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09/05/2005 12:20:56 PM · #10 |
| Thank you thank you thank you. I am also starting to think about purchasing a DSLR as soon as the budget allows and I have many many times wondered about all these lenses! The explanations here have been most helpful! Gotta love this site :) |
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09/05/2005 12:29:57 PM · #11 |
Welcome Al.
As far as the focal length of the lens goes, (that is, the mm), back before digital cameras arrived it was generally accepted that a 50mm lens was a "normal" focal length and that it most closely approximated how people actually view their surroundings. Smaller focal lengths are referred to as wide angle lenses, and larger focal lengths are telephoto. Of course there are slight to extreme examples of each. For practical purposes, the range runs from about 10mm ultra wide-angle to 600mm super-telephoto, although for really huge sums of money even these lens sizes can be exceeded.
Now for a bit of a complicating factor. With the advent of digital, there is what is known as a "crop factor". The Canon Rebel has a 1.6 crop factor, so there is a 60% increase in the effective focal length of a lens. Now a "normal" 50mm lens has an effective focal length of 80mm (50 X 1.6). This generally works to the advantage of telephoto lenses since they have more magnification, and to the detriment of wide-angles since their performance is inhibited.
Also be aware that the crop factor does vary from digital camera to camera; I mentioned the Rebel because that is what you are planning to purchase.
Hope this will be helpful to you. Anyone spotting any errors or points of confusion that I might have made, please correct me. Good luck Al.
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09/05/2005 12:30:09 PM · #12 |
Several Pages from the Canon Enjoy!Digital SLR Cameras... Great site for anyone just starting or thinking of getting a dSLR. Tons of great info you may want to bounce around the site once there.
Different Lenses
Angle of View
How the Lens changes the picture
Enjoy
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09/05/2005 01:12:53 PM · #13 |
As far as TC's (seen one mentioned below) I would consider (I have had great results with mine) the:
Kenko Teleplus Pro 300 x1.4 or x2.0
About 100 bucks less then Canon's, it has great Hoya glass in it and you are not limited to what lenses can be mounted on it (except for the EFS lenses. They are the only Canon mount lenses that won't mount)
I throw my 50mm 1.8 MKII on mine from time to time and it is just peachy.
I paid $147.00 for a new in box one on eBay for mine.
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09/05/2005 01:18:37 PM · #14 |
Originally posted by nova:
Welcome Al.
As far as the focal length of the lens goes, (that is, the mm), back before digital cameras arrived it was generally accepted that a 50mm lens was a "normal" focal length and that it most closely approximated how people actually view their surroundings. Smaller focal lengths are referred to as wide angle lenses, and larger focal lengths are telephoto. Of course there are slight to extreme examples of each. For practical purposes, the range runs from about 10mm ultra wide-angle to 600mm super-telephoto, although for really huge sums of money even these lens sizes can be exceeded.
Now for a bit of a complicating factor. With the advent of digital, there is what is known as a "crop factor". The Canon Rebel has a 1.6 crop factor, so there is a 60% increase in the effective focal length of a lens. Now a "normal" 50mm lens has an effective focal length of 80mm (50 X 1.6). This generally works to the advantage of telephoto lenses since they have more magnification, and to the detriment of wide-angles since their performance is inhibited.
Also be aware that the crop factor does vary from digital camera to camera; I mentioned the Rebel because that is what you are planning to purchase.
Hope this will be helpful to you. Anyone spotting any errors or points of confusion that I might have made, please correct me. Good luck Al. |
In practical terms, this means that to get "reasonable" wide-angle coverage of the Rebel you need a lens of 17-18mm or shorter. On the other end, 200mm is quite a bit of telephoto on the Rebel; the equivalent of 320mm on a conventional 35mm camera or a full-frame digital camera. A "normal" lens on the Rebel would be in the 30mm range.
R.
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