Cheap Lenses or the difference between F 3.5 - 5.6

Discussion in 'Beyond the Basics' started by Vautrin, Dec 9, 2008.

  1. Vautrin

    Vautrin No longer a newbie, moving up!

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    Hi,

    So for maybe five months or so I've been taking pictures with my Olympus EVOLT 510.

    And I love it, and I've slowly been trying to experiment to figure out new things to do. You know, all the cool effects. Big panorama postcard? Bought autopano to see if I could make one. Crazy HDR landscapes? Some time with photomatix was well spent.

    The newest thing I am trying to see is if I can take a picture with a subject that is very crisp in the foreground, with a blurry background. Or make sure that if I take a picture of a landscape with houses and such that everything is crisp throughout the picture.

    I did some research and wikipedia has a great shot of how you can use the aperature, and shows the difference between f 5.6 and f 32 and it's striking.

    But the lenses that came with my evolt are f3.5-f5.6 which is a very small range.

    And the difference between those (what is that, 2 stops??) doesn't really seem noticeable.

    Would I be right in suspecting I just have a cheap lens and would need to shell out big bucks for something that could go from f2 to f32?

    When I look up the "professional" grade olympus lenses they only appear to be for f2, is that right? I assume that's because most people want "fast" lenses?

    Am I even right that my landscape photos (panos and such) would clear up if I used a higher number f stop? I figured iso 100 f32 long shutter speed would make some really incredible panos, is that right?

    Thanks,

    Dan
     
  2. McQueen278

    McQueen278 TPF Noob!

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    Don't worry, you actually have a pretty nice lens if it is an Olympus. I am assuming it is the 14-45mm f/3.5-5.6? When it says f/3.5-5.6 it means that the largest aperture is f/3.5 at the widest end (14mm) of the lens and f/5.6 at the longest end (45mm) of the lens. Your lens should have the capability of going from f/3.5 all the way to f/22 or f/32. Almost all lenses go to at least f/16 and most go to f/22 while some go to f/32.

    Also, I wouldn't go any higher than f/11 with your lens. Pictures get softer past that because of something called diffraction.

    If you want to achieve the effect of having a subject in focus and the background blurred you might ant to get a little bit of a "faster" lens like the 25mm f/2.8 Pancake lens from Olympus. The larger the f number, the more of the picture will be in focus so the f/2.8 of the pancake lens will give you a more narrow band of focus than the f/3.5 of your current lens. You can do what you want to do with the lens you have, it will just be a bit trickier. The 25mm f/2.8 is a really nice lens and not terribly expensive either. It runs something like $280. It is well worth it for an Olympus owner.
     
    Last edited: Dec 9, 2008
  3. dxqcanada

    dxqcanada Been spending a lot of time on here!

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    McQueen is correct .. that is the widest aperture your zoom lens can achieve at the smallest and longest focal length.

    You will achieve more depth of field with a smaller (ie f32) aperture.

    The smaller the aperture will require more exposure so you will need slower shutter speeds ... have a tripod handy.

    From Wikipedia:

    The photography term "one f-stop" refers to a factor of √2 (approx. 1.41) change in f-number, which in turn corresponds to a factor of 2 change in light intensity.

    1.4 - 2.0 - 2.8 - 4.0 - 5.6 - 8.0 - 11.0 - 16.0 - 22.0 - 32.0
     
  4. bigtwinky

    bigtwinky No longer a newbie, moving up!

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    As stated, the numbers on your lens show you the widest aperture your lens can go to. The reason it shows a range is because it will have a different max of 3.5 at the shorter focal length to 5.6 at the longest focal length.

    The professional lenses you see that are showing f2.0 have a max wide aperture of 2.0. If this is the only number shown, then it has a constant max aperture of 2.0, regardless of its focal length.

    Ex:
    14-45mm f2.0 would have a max aperture of 2.0 at 14mm AND at 45mm (and anywhere in between). It can also go as high as something like f22 or so
     
  5. Garbz

    Garbz No longer a newbie, moving up!

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    Just note that f/22 or f/32 is something that is brought over from the film era. Modern DSLRs have smaller sensors and suffer from diffraction related sharpness problems at a lower aperture. It is still possible to take photos at f/22 but at a very notable drop in sharpness. Try to stick below f/16 if possible.
     
  6. sabbath999

    sabbath999 No longer a newbie, moving up!

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    This is especially more apparent the smaller the sensor... not an issue with a full frame digital (the D3/D700 for instance). Much more noticeable in 1.5 or 1.6 crop factor cameras like the lesser, and even more so in the 4/3rds cameras. About the only use I can think of for that high of an aperture is macro work.
     
  7. TBAM

    TBAM TPF Noob!

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    Hey.

    It's good to see some Olympus topics on here.

    Getting small depth of field isn't just about your aperture value. It is also to do with your focal length, distance from subject and subject's distance from the background.

    I have the 14-42 and 45-150 and I can easily get small depth of field with both, but it is usually either when very close up, or with the focal length extended considerably.

    The 45-150 on a bright day actually works out to be a half-decent portrait lens if you don't have anything else available.

    McQueen, so the 25mm 2.8 is good eh? I was a bit worried that with a focal length of 25mm and less than a stop of difference between the kit lens, it would not be that great a difference or that advantageous to spend $300 + AUD on as opposed to spending $500 or so on the sigma 30mm f1.4 I think it is.

    Also, with the E-30 coming out soom, there will be a new 14-40 or so kit lens with a constant aperture of f2.8 on the market, and may be able to be picked up cheap.

    Just curious, I understand the 4/3 sensor is a 2x crop factor, which means the 25mm f2.8 is "really" a 50mm f2.8. However as the focal length is still 25mm but a field of view akin to 50mm do the depth of field calculations / effects get based on 25mm or 50mm?

    Or are the 4/3 lenses like the DX lenses on Nikon where the lens shrinks the image onto the sensor?
     
  8. McQueen278

    McQueen278 TPF Noob!

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    4/3 lenses "shrink" the image circle. The DOF is like a 50mm, the same way that 80mm has a similar field of view on medium format to a 50mm lens on 35mm format. 4/3 sensors are just a very small format and the lenses are designed specifically for that format so they really shouldn't be thought of as standard 35mm format lenses on a crop body, they should be thought of as 4/3 lenses on a 4/3 sensor. 11mm being wide angle, 25mm being normal and 50mm being a short telephoto.

    Also, to anwer your question about the 25mm f/2.8, YES it is good. 4/3 zoom lenses have to be shorter than 35mm format lenses to achieve the same field of view so they are even MORE complex than say the Canon 24-105mm f/4 L. That is why even the amazingly sharp (corner to corner) and low distortion 14-54mm f/2.8-3.5 still isn't a constant aperture lens like the Canon 24-105mm f/4L which has a very similar field of view. SO... a prime lens that is designed specifically for the small 4/3 format can, through it's more simple design, be of much higher optical quality. In short, it is a prime lens and much sharper and has no distortion worth mentioning.
     
  9. LWW

    LWW TPF Noob!

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    HUH?

    F stops are as valid today as they were at any time in the past.

    Quality will suffer at uber small apertures such as F32 on a digicam. The same was true in film.

    Most lenses will deliver thir optimum quality at 2-3 stops from maximum aperture.

    IOW, an F2.8 max aperture lens will almost always deliver max sharpness at F5.6 to F8.

    At X ISO and Y shutterspeed Z aperture is required for a proper exposure.

    Whether the medium is film or digital makes no difference.

    LWW
     

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