Lenses - how can you tell how good they are?

Discussion in 'Beyond the Basics' started by Don Simon, Aug 1, 2005.

  1. Don Simon

    Don Simon TPF Noob!

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    Now this truly is a newbie question. Given the number of used cameras I've been collecting I should really know more about lenses, since they're probably more important than the camera body. Unfortunately I know very little about lenses; in particular I have no idea how to tell if a lens is good or not - apart from shooting a roll of film with it and looking at the results, and even then I'm not someone who can look at a 7x5 print and assess the quality of a lens from it. I assume that a "prime" lens is one that costs more to make and a lot more to buy, but that's about all I know.

    So far when buying used lenses (mainly Pentax K-mount) I've tended to look for names I know - Sigma, Vivitar, and.. er, well anything that sounds vaguely Japanese (Takumar, Sunagor etc) to be honest :D As I understand it though, pretty much any lens manufacturer is capable of producing great quality lenses and equally capable of producing useless paperweights. So I also tend to look for lenses with a wide range of apertures - I have no idea if this gives any indication of lens quality however.

    At the moment I'm buying a used Minolta Dynax 5 (albeit with non-functional flash) to replace my slightly rubbish 404si, and I'm wondering if I should be getting a new lens to go with it. I guess what I'm looking for here is not advice on a specific lens to buy, but some idea of how to tell the quality of a lens. At the moment I have a Tamron 28-200mm F/3.8-5.6 lens which is apparently "LD Aspherical (IF)" - which could be Martian for all I know - and is described as "Silver Super", which I can only assume means it's better than the bronze but not as good as the gold :meh: Minimum focussing distance is 0.8m at 200mm, and "Max. Mag. Ratio" is "1 : 4.8" at 135mm. Which also means nothing to me. I also have a Tokina 19-35mm F/3.5-4.5 lens, for which I have no manual and therefore no idea what the minimum or maximum anything is. I've taken some perfectly good photos with both lenses, but having nothing to compare them against I have no idea if I could be getting much better results. Finally I have a Sigma "Mini Zoom Macro" 28-80mm F/3.5-5.6 lens which is also "Aspherical" and has macro-focussing at 80mm. I bought this new for only £50 (shipped from US) which seems very little for a new lens, and the exterior appears to be entirely plastic, yet I've taken some great close-up shots with it. Again however I have nothing to compare it against.

    So basically what I'm looking for is any advice at all on how to tell whether a lens is good quality or not; what on earth "LD Aspherical (IF)" means and whether it's better than simply "Aspherical", the significance of how curved the lens elements are... pretty much anything you can think of :) Thanks in advance, and also for the help you've all given me already in my other posts :hail:
     
  2. Meysha

    Meysha still being picky Vicky

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    Prime lenses are generally sharper than zoom lenses just because there are minimal moving parts - less room for sharpness error.

    Easy answer - Price. you get what you pay for.

    Also do a search for reviews of the lenses on the net. As you said, lenses vary greatly even within the same company, so do a google on the lens and see what pops up. It's a little hard i reckon for one little community like tpf to know all the lenses out there - impossible actually. So google would be your safest bet. That, and price.
     
  3. westman

    westman TPF Noob!

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    mainly the sharpness and richness of colours
     
  4. Don Simon

    Don Simon TPF Noob!

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    Thanks for the advice - as you say price can be a good indicator, but I'd think is less appropriate when buying used lenses off Ebay (and even when buying new I'm still pretty sure you can get very good lenses for sensible money, depending on the manufacturer and the materials used). I guess as Westman says the best way to tell is to look at the photos produced with the lens, so there's probably no real way for me to know without borrowing or buying the lens and shooting a roll of film through it... back to square one :( Never mind, thanks again for the help!
     
  5. selmerdave

    selmerdave TPF Noob!

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    For Pentax K-mount stick with SMC Pentax lenses (including SMC Pentax-M and SMC Pentax-A), the only bad one I know of is the SMC-A 135/2.8. Also stay away from the Takumar 135/2.5 but it's not an SMC. "Prime" just means fixed focal length as opposed to "Zoom", for the same money you will always get a better prime I believe.

    Dave
     
  6. becca

    becca TPF Noob!

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    I would look for reviews on a particular lens (photographyreview.com is a good place to start). Price is a good general gauge, as your cheaper lenses are usually cheaper for a reason. :) The lens speed (max aperture) as well as zoom factor are indicators of lens quality as well.
     
  7. thebeginning

    thebeginning TPF Noob!

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    yeah, sigmas can be good, but mainly only their newer autofocus ones have reviews online. vivitars are rarely good. i would suggest sticking with pentax lenses and going to photographyreview for reviews as well. oh, and 'prime' actually means that it's just not a zoom lens. like it's just one set focal length. a 28mm prime is a 28mm lens (semi-wide angle). a 50mm prime lens is a standard 50mm lens (50mm is supposedly the closest resemblence to how we see with our eyes).
     
  8. selmerdave

    selmerdave TPF Noob!

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    There is certainly some truth to this (especially when comparing the same lens between brands) but often you are paying for flexibility rather than sheer image quality. For example a 50mm f2 lens is likely going to be one of the cheapest lenses you could buy, and I think it would be wrong to assume that the 28-80 f2.8 lens that costs several times the price is going to give you any better image quality. Same with a 50mm f2 compared to a 50mm f1.2, the second probably is ten times the price and yet the image quality above f2 is likely identical with both lenses. In keeping with the above quote, though, I don't think anyone makes a lousy 50/1.2.

    Dave
     
  9. becca

    becca TPF Noob!

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    They were two separate thoughts, actually. I should have made that more clear. As far as price goes, if you see two zoom lenses of comparable focal length, but the prices are radically different, chances are good that the more expensive lens is better.

    As far as zoom factor goes, I mean to compare zoom to zoom lenses only. A higher zoom ratio (I'd say more than 2.5X) is usually going to come at a cost of quality.

    Fixed focal length lenses are a different beast altogether. :) Sorry for any confusion.
     

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