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Thread: camera question

  1. #1

    Default camera question

    hey guys I was hoping some of yall could explain the difference between a EFS 18-55mm f/3.5-5.6 and a 20mm f2.8 lens for the canon digital rebel XTi

    Thanks,

    Richie

  2. #2
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    The first set of numbers (18-55 and 20) are the lens' focal lengths in millimeters when the lens is focused at an infinite distance. the smaller the number the wider the angle of view, and the larger the number the narrower the angle of view. Wide angle lenses show a whole lot of stuff, but everything in the image looks quite small. Longer length lenses show less, but everything look larger, like looking through a telescope. The 18-55 means that it is a zoom lens that is quite wide at one end, and a short telephoto lens at the 55mm end. The 20mm is a wide fixed length lens, called a prime lens.

    The second set of numbers (f/3.5-5.6 and f/2.8) are the lens' maximum apertures. This is expressed as a ratio or fraction, so f/2.8 means that the maximum inside diameter of the lens is 1/2.8 times (roughly 1/3) the focal length of the lens. Since the lens is 20mm long, f/2.8 specifies that the lens has an inner diameter of 5.6mm. That bunch of technical mumbo-jumbo is mostly meaningless, but the bottom line is the smaller the f/number the more light is let through to the film or digital sensor. This is a good thing because it allows you to shoot in less light while still keeping the shutter speed high enough to hand hold the camera. If the shutter speed falls off too much, you get blurry pictures from camera shake.

    It just happens that the Canon 18-55 is a cheap lens of medium to good image quality, and the 20mm is a high quality lens that costs more and performs better.

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    Another thing to consider is the larger the apeture opening (smaller the F stop number) the less depth of field you will have in the final photograph. This means less of the entire area will be in focus. You can get into some pretty neat stuff calculating hyperfocal distances with small aperture lens.
    Every thing in photography is a trade off of one sort or another.
    Good shooting!
    Tennessee

  4. #4

    Default thanks guys..

    you started to lose me there for a second...but I think I'm tracking now. I appreciate yall explaining the ins & outs...I just didn't want to spend all that money and not understand what I was getting into.

    thanks again,

    Richie

  5. #5

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    hey guys I had one more question...where is a good place to look online to find a good price on that 20mm f2.8 lens

    thanks again,

    Richie

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    EricL

  7. #7
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    Default

    Eric's right about B&H Photo. They are not only the largest photo dealer in the world, but probably the most reliable of the large discount dealers. Adorama is another with a generally good record. You can find cheaper advertised prices elsewhere, but if there is a large discrepancy in price from B&H's posted prices you can bet it's a scam of some sort.

    I also sometimes buy from Amazon as well. They're reliable and offer free shipping to Alaska on most items that they sell directly. But my biggest complaint is that they do a lot of selling for other dealers as well, and some of those are not on the ball so much. If they offer free shipping, it's a good bet that Amazon is really the direct seller.

    On rare occasions I find local dealers competitive, so you might want to check them out.

    BTW, the cheap Canon 18-55 has been updated with Image Stabilization, and improved optics. This version is about $180, but is reputed to be surprisingly sharper, and the inclusion of IS makes it a very good low cost zoom option for Canon DSLRs. It still feels cheap, and f/5.6 is on the "slow" side of cheap zooms.

    Also, if you are looking for a better lens for your camera, you might want to consider some other options. A "normal" lens for a Canon digital would be in the 30mm range, so either a 28mm or 35mm would suit most users better for most things. Canon's 35mm f/2 is optically very good and reasonably priced. And the undisputed value lens is always Canon's 50mm f/1.8. It's a short telephoto lens when used on a Canon digital camera, but the optics are superb for the usual $80 price tag. The 20mm is kind of wide for general purposes, but is a good lens if you have a call for it.

  8. #8

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    thanks jim and eric for the advice on where to try and find a good deal. Jim, has far as getting the right lens I got a lot to learn bc I'm not sure which one to buy. I just really want to get some pictures of the northern lights and I was told the 20mm f2.8 was the lens to go with. Do you have any advice on what lens I should buy if thats what I'm looking to do?

    Thanks again,

    Richie

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    I was wondering if you just bought the cannon 40D camera body I found a add for 499.00. What lenses will fit the body like the 20d, 30d.
    Is that a good deal for the camera body.

  10. #10
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    Richie: Yes, the 20mm f/2.8 is a good lens for shooting Northern Lights. For that you usually want a wide lens. But in my opinion, the cheap 18-55 that often comes with Canon digital SLRs might be nearly as good for that job. It's quite sharp in the 18-30mm range and at 18mm it is f/3.5, which is pretty close to the f/2.8 of the 20mm lens. The 20mm will be better, but perhaps not by a great deal. If you have one of the cheap zooms, I would recommend trying it before deciding to upgrade. Either way you will want a sturdy tripod and a remote shutter cord. You can buy Canon's cord, but it's not cheap for what it is. The third party offerings from China (sold on eBay) are a better deal.

    matsuthunder: Any place advertising the Canon 40D for under $1100-1200 right now is a scam. Give it a year and they might get down closer to $1000 - maybe. Check out unknown sellers at http://www.resellerratings.com/ On the other hand, if what you saw was a Nikon D40 for $500, that would be expected, but it's not at all in the same class.

    Any Canon EF or EF-S mount lens (all their autofocus lenses) will work fine on any Canon digital SLR. Also several third party manufacturers make EF mount lenses that work well on them, but you usually do get what you pay for. And some older Sigma lenses will not work with newer Canon cameras, so be sure you know what you're buying if looking at used lenses. None of Canon's old manual focus FD or FL mount lenses will work on any of the digitals. In addition, Nikon F mount, Pentax M-42 mount, and several others can be made to work with the right adapters, but you loose auto aperture, auto focus, and they may not meter correctly either.

  11. #11

    Default hey guys...

    I've been looking around and came across these and was hoping yall could give some input on what yall thought about them...thanks again

    http://www.amazon.com/Sigma-18-50mm-...61508&sr=1-118

    http://www.amazon.com/Sigma-17-35mm-...361993&sr=1-25

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    Well, I've owned both of those Sigma lenses, and wasn't very happy with either. Optically, the 18-50 f/2.8 was the better of the two, but autofocus was hit or miss in less then bright light. I had too many shots that I had to reject for poor focusing when shooting indoors. There has been quite a lot of comments on the internet about this lens having focusing issues, so it wasn't just the one I had. I could get mine to cooperate if I stabbed the shutter button half way several times until the AF stopped moving about.

    But if you do decide to get one, get the newer version ( http://www.amazon.com/gp/product/B00...61508&sr=1-118 ) It has "Macro" in it's name, and focuses a bit closer. It's also supposed to have better sharpness in the corners. Unfortunately, the AF is unchanged.

    Tamron's 17-50 f/2.8 is said to have excellent optics and be better focusing than the Sigma, but more than a few have complained about poor focusing with it as well. Here is a thread on that: http://forums.dpreview.com/forums/re...hread=24033377
    I finally gave up trying to save money on the lens I use the most, so I bought the Canon 17-50 f/2.8. Now *that* is a sweet lens. Very sharp, fast accurate focus, full time manual focusing too, and image stabilization that works wonders. Too bad it costs $1000.

  13. #13

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    man, all these bad reviews got me pretty nervous about trying to buy a lens for the camera I want. Jim, your lens sounds awesome but thats a little out of my price range...what would you do if you were in my situation...would you go ahead and buy the camera with the 18-55mm that comes with it or just buy the body and get a lens seperate?

    Thanks again,

    Richie

  14. #14
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    The only reason I spent the money on the Canon 17-55 f/2.8 was because I was making money shooting, and the other lenses were making it difficult to do that reliably. Normally, I can't bear to part with that much money on a piece of glass, and can totally appreciate why others would balk at it.

    Personally, I would either get the new Canon 18-55 IS (the older non-IS version really isn't so bad, it's just not as good and lacks IS), or I would buy the Tamron 17-50 f/2.8. You might have focusing issues with the Tamron, but if you buy it from a good dealer you can send it back for a replacement without hassles if needed. Everyone who has had one agrees that if you get a good one, it is very good indeed.

    Another "totally out of left field" option is to get Tamron's newest 18-250 IS lens. Every report I've read fairly raves about it considering its radically long zoom range. It will have some optical compromises though. It wouldn't be my first, or even second choice, but it isn't a bad option.

    I should disclose that I have become generally prejudiced against Sigma lenses. I didn't start out this way, but I have bought too many of them, and been disappointed too many times. I know they make some good lenses and some not so good lenses, but I personally think there are reasons concerning quality why Sigma is usually less expensive than the other brands. I may still buy another in the future because I'm such an optimist and a cheapskate, but I fully expect to be disappointed again.

  15. #15

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    hey guys just wanted to say thanks for all the great info...I decided to go with the rebel XTi 10.1 MP with the 18-55 IS lens and I just got it in the mail today and I love it. Granted I really don't know what I'm doing but so far the pictures have turned out awesome!

    Richie

  16. #16
    Member danattherock's Avatar
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    Smile Glad to hear....

    Richie,
    Congrats on the new camera. Jim Strutz will keep you straight. He offers some real good advice. He has helped me here and on photo.net (great photography forum with lots of activity). I got my first DSLR last month, a Canon EOS 40 D. I got the 10-22 lens last week and can recommend it highly. My camera came with the 28-135 lens. I have already taken some of the best pictures of my life. I would add to what Jim said in telling you to buy a book. Jim is an experienced photographer but I am not. If you are more like me than he, get a few books. I went to www.barnesandnoble.com and put Canon 40d in the search engine. Got lots of books specific to my camera. You can get the same (actually more) for your camera. One that looks real good to me is the Field Guide books. Title would be like "Field Guide for the Canon EOS 40D" etc.. I also found an instructional DVD for my camera. That helped me learn some of the features of the camera much faster than I would have otherwise. And ditto on what he told you about B&H Photo/Video. They are awesome. I have made several purchases with them over the years and they are a joy to deal with. Best prices you will find. Matter of fact, if you see a price advertised lower than B&H, it is likely a scam. Check on any suspicious businesses online at www.resellerratings.com Enjoy your new camera!! Below is a link to a few I took last week here on Nantucket, Mass with mine.

    Click the below links and then select "view slideshow" which is above the pictures on right side of page.

    http://www.flickr.com/gp/21144083@N02/068w57

    http://www.flickr.com/gp/21144083@N02/2EHGWR

    http://www.flickr.com/gp/21144083@N02/c59i3X
    The two loudest sounds known to man: a gun that goes bang when it is supposed to go click and a gun that goes click when it is supposed to go bang.

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    Oh-oh, Dan. Keep that up and people are gonna expect me to take pictures instead of just talkin' cameras.

    Earlier in this thread I said, "Any place advertising the Canon 40D for under $1100-1200 right now is a scam." Well, today I found that if you go to B&H an type "ps1107bngu5" in to their search box you can find a Canon EOS 40D Body priced at $1119.00. That price won't last, but this is the first time I've seen a new Canon DSLR drop in price so fast. Competition is good --- for the consumer.

  18. #18
    Member danattherock's Avatar
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    Smile Modesty...

    Jim,
    A forum is no place for modesty! Ha ha. Seriously, thanks for all the help you offered over the last few months. Of all the opinionated responses (sometimes too sharply) I have gotten, yours have always kept me on the right path. I now have a Canon 40D, 10-22 lens, Photoshop Elements 6.0, and several books. Six weeks ago I had a point and shoot camera that I used on the dummy mode. When I figure out what to do with it I will be dangerous. I can promise you by the time I step foot on the banks of the Wulik in Sept, I will be ready to get some good shots. Hoping to get up to Chena in March for some lights. Thanks for all the pointers!
    The two loudest sounds known to man: a gun that goes bang when it is supposed to go click and a gun that goes click when it is supposed to go bang.

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