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  1. #1
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    Digital and Digital SLR lens question

    Hello everyone, I am new here so forgive me if this is a question that has been answered 5000 times on this site already. I have an Olympus C-720 which is old as dirt. I am considering purchasing a Nikon D50 but I am undecided on what focal length lens I want to get. The one thing I like about about SLR-like digital cameras is the amount of optical zoom they boast. My Olympus has 8X zoom so I want to make sure I have at least the same amount of "reach out and touch something" power. I have recently stumbled across the term, focal length multiplier or FLM for short. My understanding of how to get this number is by taking the diagonal measurment of 35mm film (43.3mm) and dividing the diagonal measurement of the digital sensor into it.

    Olympus C-720
    Sensor size - 5.27 X 3.96 = 6.592 diagonal ----------- 43.3 / 6.592 = 6.56X FLM.
    Actual focal length - 6.4mm - 51.2mm ---------- 6.56((6.4)(51.2)) = 41.984mm - 335.872mm.
    335.872 / 41.984 = 8 times optical zoom exactly.
    Olympus puts the 35mm equiv. of this lens at 40mm - 320mm, which divided gives 8X

    So what I get with the camera above is fantastic zoom with only a 6.4mm - 51.2mm lens because of the ridiculously small sensor that produces a very cropped image. Now lets look at the Nikon D50.

    Nikon D50
    Sensor size - 23.7 X 15.5 = 28.3185 diagonal ------------- 43.3 / 28.3185 = 1.529X FLM.
    Example DSLR lens - 70mm - 300mm ---------- 1.529((70)(300)) = 107.03mm - 458.7mm.

    This is the part that confuses me. I can use the same method that was used to determine the power of the C-720 or I can use the method that consist of taking the telephoto end of the focal length and dividing that by 50mm (what the human eye sees).

    C-720 method - 458.7 / 107.03 = 4.23 times optical zoom
    / 50mm method - 458.7 / 50 = 9.174 times optical zoom

    Which is right??? My reasoning leads me to determine that with a 300mm zoom lens on the Nikon D50 I would have more zoom than the C-720 does. Something else just occured to me - If I take the FLM focal length of the C-720 and divide that by 50 it gives me 6.72 times optical zoom. So does the C-720 have 8X zoom or 6.72X zoom? Thanks alot! Sorry this is so long.

    Nathan

  2. #2
    Sleep is optional Sebastian's Avatar
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    Re: Digital and Digital SLR lens question

    All the math is nice, but the manufacturers of DSLRs already give you the crop factor (1.5 for the D50) and all you have to do is magnify the focal length by that number.

    That being said, you want to avoid the large zoom ranges. As a rule of thumb, the larger the zoom range (28-300 for example) the worse the optics. To be able to squeeze such range into a lens means making compromises. I suggest getting the D50 and some really cheap, and really good, used primes. Primes, if you don't know, is the name for fixed-focal-length lenses, or non-zooms. Those will give you MUCH nicer optics, larger apertures to let more light in, and the only drawback is having to change lenses. Which, really, isn't a drawback at all.
    -Seb

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  3. #3
    has-been... another view's Avatar
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    Re: Digital and Digital SLR lens question

    Just make sure that the prime lenses (any lenses) for this camera are AF or autofocus lenses. If they're not, then the in-camera metering won't work.

    There are some zooms with pretty good optics, although primes generally are better. The "kit" lens is probably not that great for the D50 but you might look at getting it instead with the 18-70 lens that comes with the D70s instead. I've never used it but heard that it's a good lens for the price.

    Like Sebastian said, the more the "X" doesn't usually mean that it's a better lens. Optically, usually the opposite is true.

  4. #4
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    Re: Digital and Digital SLR lens question

    O.K. that all makes sense. I need to find some prime AF lenses that are used and cheap. So, where would i look to find these lenses and what brand would I be looking for. I just went to the sigma website to check out a 300mm fixed focal length lens and then looked that lens up on ebay and it was close to 2000 dollars! I understand that the lens is just as important as the body but if I could afford a 2000 dollar lens I would'nt be buying a 600 dollar body. Any suggestions would be greatly appreciated. Thanks alot!

    nathan

  5. #5
    has-been... another view's Avatar
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    Re: Digital and Digital SLR lens question

    Usually the third party manufacturers (Sigma, Tokina and Tamron) only make specialty prime lenses like Macro lenses and big fast teles. If you're looking for more general use primes, stick with Nikon. KEH is a good source for new and used lenses.

  6. #6
    Sleep is optional Sebastian's Avatar
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    Re: Digital and Digital SLR lens question

    Nathan,

    That is an f/2.8 lens, and that is very cheap for one. You don't need the f/2.8 aperture, and you probably don't even really need the 300mm unless you find yourself shooting soccer, high-end football or are REALLY into wildlife.

    The thing that needs to be clear, is that we're not saying "don't ever buy zooms." We're simply saying a 28-300 zoom will give you noticeably lesser quality that the camera is capable of. The pictures will still be very nice compared to P&S pics, but a nicer lens will get you much more.

    Both Nikon and Canon make a 300 f/4 which is about $1000, but can be had used for less. The best bang for the buck would be a 180mm f/2.8 which can be had for about $340 on KEH.com in excellent condition. This is a great lens.

    I should also mention that you really should not get too caught up in focal lengths. Yes, 300mm gets you range, but you can save money, get better optics with shorter focal lengths, and simply use your feet to "zoom." Changing focal length is almost never used to bring things closer anyway, it is used to change the way the image looks. That's why you'll see experienced photogs change lenses and move to a different location to keep framing the same, but make the photo look different. Different focal lengths have different distortion, perspective and depth of field qualities, and that's why zooms are nice, because they replace having to carry and swap multiple prime lenses not to "bring things closer."

    But none of that might be important right now to you. If you want a 300mm, get what you can afford. But if you want to realize the potential of the SLR, consider making compromises in focal length and convenience.
    -Seb

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  7. #7
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    Re: Digital and Digital SLR lens question

    I donno man...i find f2 useful

  8. #8
    Sleep is optional Sebastian's Avatar
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    Re: Digital and Digital SLR lens question

    Quote Originally Posted by 92135011
    I donno man...i find f2 useful
    Thank you for your profound statement. I now have a new outlook on life.
    -Seb

    My website

    (Please don't edit and repost my images without my permission. Thank you)

    How to tell the most experienced shooter in a group? They have the least amount of toys on them.

  9. #9
    has-been... another view's Avatar
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    Re: Digital and Digital SLR lens question

    I use f1.4 often enough too, but in special situations when I need the shutter speed in low light or for the effect of very little depth of field. IOW, it's not an "everyday" type of occurance.

    I'm going to stick with my 18-70 recommendation for your main lens, and also add a 50 f1.8 for under a hundred bucks if you want a really sharp, really fast prime for an absolute bargain. I have a couple of zooms that are very sharp, and I'm going to say that they rival primes here. Mostly I shoot with zooms. I have a couple of great Nikon primes, and they're better than zooms in some cases but in most "normal" situations zooms will be great.

    Anyway, lens sharpness is over-rated IMO. Unless you're shooting on a heavy tripod and using mirror lockup and/or a cable release, it's not the biggest issue with getting a good image. If you're shooting handheld, camera shake is a bigger problem than lens sharpness can correct. Composition (and other aspects that can't be qualified by numbers) beats sharpness anyday in my book.

  10. #10
    Be serious Franglais's Avatar
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    Re: Digital and Digital SLR lens question

    Quote Originally Posted by nathanmixon
    Hello everyone, I am new here so forgive me if this is a question that has been answered 5000 times on this site already. I have an Olympus C-720 which is old as dirt. I am considering purchasing a Nikon D50 but I am undecided on what focal length lens I want to get. The one thing I like about about SLR-like digital cameras is the amount of optical zoom they boast. My Olympus has 8X zoom so I want to make sure I have at least the same amount of "reach out and touch something" power. I have recently stumbled across the term, focal length multiplier or FLM for short. My understanding of how to get this number is by taking the diagonal measurment of 35mm film (43.3mm) and dividing the diagonal measurement of the digital sensor into it.

    Olympus C-720
    Sensor size - 5.27 X 3.96 = 6.592 diagonal ----------- 43.3 / 6.592 = 6.56X FLM.
    Actual focal length - 6.4mm - 51.2mm ---------- 6.56((6.4)(51.2)) = 41.984mm - 335.872mm.
    335.872 / 41.984 = 8 times optical zoom exactly.
    Olympus puts the 35mm equiv. of this lens at 40mm - 320mm, which divided gives 8X

    So what I get with the camera above is fantastic zoom with only a 6.4mm - 51.2mm lens because of the ridiculously small sensor that produces a very cropped image. Now lets look at the Nikon D50.

    Nikon D50
    Sensor size - 23.7 X 15.5 = 28.3185 diagonal ------------- 43.3 / 28.3185 = 1.529X FLM.
    Example DSLR lens - 70mm - 300mm ---------- 1.529((70)(300)) = 107.03mm - 458.7mm.

    This is the part that confuses me. I can use the same method that was used to determine the power of the C-720 or I can use the method that consist of taking the telephoto end of the focal length and dividing that by 50mm (what the human eye sees).

    C-720 method - 458.7 / 107.03 = 4.23 times optical zoom
    / 50mm method - 458.7 / 50 = 9.174 times optical zoom

    Which is right??? My reasoning leads me to determine that with a 300mm zoom lens on the Nikon D50 I would have more zoom than the C-720 does. Something else just occured to me - If I take the FLM focal length of the C-720 and divide that by 50 it gives me 6.72 times optical zoom. So does the C-720 have 8X zoom or 6.72X zoom? Thanks alot! Sorry this is so long.

    Nathan
    Let's define some terms:

    Zoom = ratio between shortest and longest focal length of a (zoom) lens. This says nothing about what the actual image looks like because it says nothing about what the actual focal lengths are
    Telephoto = lens view which magnifies far away objects, like a telescope
    Wide-angle = lens view which crams a maximum of the subject onto the frame
    Normal = lens view corresponding to normal human perception of a scene

    Now let's classify a few 24x36 focal lengths and what you can use them for:

    17mm = extreme wide-angle for extreme landscapes
    28mm = wide-angle, useful for landscapes, buildings, etc.
    35mm = moderate wide-angle, useful for groups and crowds
    50mm = normal, useful for pictures of couples
    85mm = moderate telephoto, for chest & head shot portraits
    200mm = telephoto, for head shots
    300mm = long telephoto, for picking out details

    So your Olympus C-720 with its lens which is the equivalent of a 40-320 gives you a range of views from short normal to long telephoto. (It's the long telephoto that you call "reach out and touch something"). However like most point-and-shoots it's not very wide-angle and must be a nuisance in confined spaces.

    If you fit the 18-70 on the D50 then it's the equivalent of a 28-105. Much better wide-angle but only a moderate telephoto. If you add a 70-300 then this is the equivalent of a 105-450 - even more telephoto than the C-720. But it means you have to carry around two lenses.

    Check out the new 18-200 VR when it eventually appears - the equivalent of a 28-300 and it has a smart vibration reduction gadget that helps you get sharp pictures in low light.

    Charles

  11. #11
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    Re: Digital and Digital SLR lens question

    I know I'm beating a dead horse here, but what do you plan on shooting with that long focal length? Do you just want it because your current camera has it? Not that it's an invalid reason.

  12. #12
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    Re: Digital and Digital SLR lens question

    Quote Originally Posted by Trevor Ash
    I know I'm beating a dead horse here, but what do you plan on shooting with that long focal length? Do you just want it because your current camera has it? Not that it's an invalid reason.
    Yeah, I am just used to it and would like to have it because I "think" I need it. As one other posted below, I can always use my legs to zoom in on an object. I enjoy photographing wildlife and this is the only reason the extra zoom would be nice. Some animals are not too crazy about letting me get really close to them for some reason. For all practical purposes, a lens with a maximum focal length of between 80mm and 125mm would be just fine. Maybe I will look for a good 28-105 lens. I can always buy a "big zoom" lens later.

    Nathan

  13. #13
    Sleep is optional Sebastian's Avatar
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    Re: Digital and Digital SLR lens question

    Quote Originally Posted by nathanmixon
    Yeah, I am just used to it and would like to have it because I "think" I need it. As one other posted below, I can always use my legs to zoom in on an object. I enjoy photographing wildlife and this is the only reason the extra zoom would be nice. Some animals are not too crazy about letting me get really close to them for some reason. For all practical purposes, a lens with a maximum focal length of between 80mm and 125mm would be just fine. Maybe I will look for a good 28-105 lens. I can always buy a "big zoom" lens later.

    Nathan
    You have the right attitude. You could always get a 180 and a 1.4x teleconverter. You would take a hit optically when using it, but it's not bad. And if you wanted the better optics, you could just not use it. You could also use it with some zooms, though you have to be careful, sometime the rear element of the lens can hit the teleconverter.

    It really comes down to what is important to you.
    -Seb

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  14. #14
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    Re: Digital and Digital SLR lens question

    Quote Originally Posted by Sebastian
    Thank you for your profound statement. I now have a new outlook on life.
    wow what sarcasm. A little grouchy today Mr. Sebastian?

  15. #15
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    Re: Digital and Digital SLR lens question

    Quote Originally Posted by another view
    Anyway, lens sharpness is over-rated IMO. Unless you're shooting on a heavy tripod and using mirror lockup and/or a cable release, it's not the biggest issue with getting a good image. If you're shooting handheld, camera shake is a bigger problem than lens sharpness can correct. Composition (and other aspects that can't be qualified by numbers) beats sharpness anyday in my book.
    true enough
    my advice is to never try to look for the best of the best all the time.
    Because you will just try and try and you will never find it.
    I have tried it and failed. I'm sure that many others shared the same fate.

  16. #16
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    Re: Digital and Digital SLR lens question

    It seems I have been looking at all the lenses that everyone makes and I think I have decided on one. The Sigma 28-105 f2.8-4 DG - I would rather have the 24-70 f2.8-4 EX DG MACRO but it is a little more than I want to spend right now. The D50 body is on its way and hopefully I will decide on this lens thing soon. It seems the 28-105 will be about $210.00. If anyone out there knows of a better lens for around $250 or less, I would love to here the suggestions. Thanks.

    Nathan

  17. #17
    has-been... another view's Avatar
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    Re: Digital and Digital SLR lens question

    I think that Sigma is pretty large, physically. If that doesn't bother you then check the reviews here - I don't have any experience with it myself. Tamron has a 28-75 f2.8 (constant f2.8, not f2.8 to f4) that I know is a very good lens and small in size. It's probably closer to $350 new but still a bargain for what it is.

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