The crop sensor lens conundrum, revisited.

Discussion in 'Digital Photography' started by soco, May 28, 2013.

  1. soco macrumors 68030


    Dec 14, 2009
    Yardley, PA
    So a while back I asked the masses about lens choice for street photography. Long story short, I decided to take the advice of shooting at one focal length on my kit 18-55mm, and seeing if it felt right.

    Well, I did, and the 18mm focal length feels perfect.

    Now, the hard part: What lens do I look for given I'm using a 1.6x crop sensor? An 18mm lens would get me a 28.8mm effective focal length, but alas, there are no 28.8mm lenses lol

    Any advice? I'm trying not to spend a boatload here.
  2. MCH-1138, May 28, 2013
    Last edited: May 28, 2013

    MCH-1138 macrumors 6502


    Jan 31, 2013
    The focal length is what it is. If you found that 18mm gave you the FOV you are looking for, that is the focal length lens you should look for. Don't worry about "effective focal length" unless you are trying to figure out which lens to use on a full-frame camera based on what lens you are using on a crop sensor (or vice-versa).

    Also, don't shortchange your kit lens if it is already doing everything you want/need. Unless you need a faster lens, want a prime, or have another reason (IQ, AF speed, etc.), it is the least-expensive solution...
  3. Bear macrumors G3

    Jul 23, 2002
    Sol III - Terra
    You aren't very clear on what you are looking for.

    If the focal length you like is 18mm, that's an 18mmm lens. You would need a 28(.8)mm lens on a full frame body for the same effect.
  4. zombiecakes, May 28, 2013
    Last edited: May 28, 2013

    zombiecakes macrumors regular

    Jul 11, 2012
    wide angle prime lenses are very expensive btw, youll probably want a 20mm, anything less than 18 and has a wide aperture gets ridiculous
  5. Attonine, May 28, 2013
    Last edited: May 28, 2013

    Attonine macrumors 6502a

    Feb 15, 2006
    Kent. UK
    If you absolutely must buy a prime, then you need an 18mm. Why not just stick with the lens you've been using?

    I think the obvious step up for you would be the 17-55 f2.8. This is quite an expensive lens though, but considered to be very good quality. Prime wise, I don't know what Canon's line up is, do they make an 18mm? There is a 20mm f2.8, don't know if it would be of any use for you though.

    What about looking for a compact or mirrorless camera with a 28mm equivalent lens. This would be particularly useful if you are continuing down the Street Photography route?
  6. seveej macrumors 6502a


    Dec 14, 2009
    Helsinki, Finland
    Ok. So what's actually wrong with using the kit lens?
    If you want A generally better lens, step up to the 2.8 zoom.
    If you want a faster lens, there's the sigma 20 mm 1.8 ( ) an ultra fast wideangle is a tricky thing to get right, but the sigma's not bad even on FF, and on crop it's outright splendid.

  7. macrumors 6502

    Aug 29, 2011
    Finding an 18mm prime is going to be tough if you're not willing to spend a lot of cash. Right now you're limited to Canon's 14mm L and 17mm Tilt Shift L (both are awesome, but very expensive). I was looking at Canon's 20mm prime for quite a while, but it's not really the best performer in the world and was just a tad wide for my taste (too much barrel distortion). I also looked at the Sigma 20mm 1.8, but it doesn't actually get that sharp until 2.8 anyway and by that time it's about the same as the Canon (but for a little less money).I ended up with the newer 24mm 2.8 IS USM and absolutely love it! It's very sharp at 2.8 (comparable to an L), has low distortion (for a wide angle) and is super small. Once I get a new body I was considering getting an SL1 to use with it for a small travel kit.

    I used it a lot with this set of photos.

    Hope this helps!
  8. someoldguy macrumors 68000

    Aug 2, 2009
    At one time Tokina made a 17mm prime . Don't know how good it was , but if you've gotta have a prime , AFAIK it's the closest to 18mm save for the Zeiss ZM which will cost you a lung to get . Maybe KEH , B&H or Adorama might have the Tokina used . OR...If the image quality you got from your 18-55 was
    OK , just stick with it . Throw some electrical tape , or maybe a real wide rubber band around the zoom ring to lock it to 18mm , pull the tape off if you want to zoom. Kinda crude but maybe it'll get you by for now.
  9. phrehdd macrumors 68040


    Oct 25, 2008
    I read some of the comments here and they seem to have their thought out points and I'll just throw my peanuts into the gallery of comments.

    If you like 18mm or so on your camera then realize it sits still in the realm of wide angle. You should learn more about wide angle lenses and their advantages and disadvantages.

    I was very active in photography during the days of film. Wide angles were almost never used wide open and usually stopped down at least 2-3 stops to get to that top level of sharpness, depth of filed, limited/reduce aberrations etc. Where a fast wide angle comes in handy these days is the ability to use the auto focus. On many cameras today, a fast lens suffers less issues in focusing in lower light than a slower lens. This is perhaps the only reason unless you are doing some "action" type of photo work.

    In the past, I have used on full 35mm 24mm, 28mm and 35mm for wide. I found the 24mm and the 35mm to have the best use for street/journalistic use AND a 85 to 90mm length as well. 24mm has a perspective that once corrected allowed for easy crop and a pleasing look while 35mm used properly seems to capture just slightly more than our own eyes see but have similar perspective. Though the 50mm is considered a standard, it is in reality slightly narrower than our own field of view and thus has a pleasing perspective. Of the latter, that is where the 85 or 90 comes in as it fully exploits this perspective that is more flattened and also allows one to be slightly further back.

    I tell you all of this because sometimes it is a real combination of hands on and understanding field of view (not to be confused with depth of field) as well as finding the best combination of f-stop/t-stop and shutter speed. You may want to see some of the lens tests shown on various sights and see the various outcomes of the tests - barrel distortion, light fall off, resolving power (and at what f-stop, again usually 2-3 stops from open wide) etc. This may be more helpful than worrying about the name brand.

    If you had the time and could rent, you may find it helpful to rent a lens or two and see how you fair with them and the results. As well, cameras such as the fixed lens Fuji X series (akin to a Leica range finder) and also Sigma's fixed lens camera with the foveon (sp) sensor would be a very usable street style camera.

    Last thought - I mentioned lens perspective and one of the biggest challenges want_to_be street photographers is understanding that if they are tall, they are often tilting slightly down on subjects. An ideal perspective to test out is to shoot with the camera about chest high (meaning either squat down or have a camera with a fold out LCD back and look down at it with the camera about chest height). Enjoy!
  10. maflynn Moderator


    Staff Member

    May 3, 2009
    Why do you need a 28.8 lens when you said that the 18mm focal length was perfect. I think you're over thinking things.

    If you determined from your kit lens that 18mm was the prefect setting, then get a prime that is closest to that for your camera. Don't worry about effective focal lengths. Crop factors and effective focal lengths seem to be subject matter people like to talk about but really have no bearing on your photography.
  11. twitch31 macrumors regular

    Feb 12, 2013
    Maybe what you need is a Ricoh GR, a street photographers dream in the focal length you want :D

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