DSLR focal length conversion & Wide-Adapters

Discussion in 'Photography Beginners' Forum' started by JeffEmbracedDC, Aug 4, 2007.

  1. JeffEmbracedDC

    JeffEmbracedDC TPF Noob!

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    Hey, guys. So, I have a Canon Rebel XT with a Sigma 18-50mm lens.

    I bought the 18mm lens because I thought it would get me an actual focal length of 18mm. After I bought the lens I realized that DSLR cameras such as mine have a smaller sensor size than actual 35mm film cameras basically causing an increase in focal length.

    I believe the conversion ratio for the rebel XT is 1.6 which means my 18mm lens actually LOOKS like a 26mm lens. If I want it to LOOK like an 18mm focal length I would have to find an 11mm lens.

    So my question is this. If I don't want to go spend $600+ on a new ultra-wide lens is there a way to get a wide type of photo from this lens? I'm not a professional by any means so image quality is not a #1 priority. Is there a way to thread wide adapter/filters on to my lens to get something close to an 18mm look?

    Basically, if I can stack one or two or three 0.45x filters on to my 18mm lens and basically get the look I want for a few bucks I'd rather do that than spend over $600 on a new 12mm canon lens.

    Thanks, guys.

    -Jeff
     
  2. killcrazy

    killcrazy TPF Noob!

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    I have a sony DSLR, with a 18-70mm lens, i have an x0.42 which bought for £30, (thats $60 to you)
    and gives me a "view" of around 7.5mm when set at its widest focal length.

    the photos it porduces are pretty good, but obviously not as crisp and perfect as a lens that costs £500 or so. but for £30.... it produces some pretty fine images.

    you will only be able to have one of these convertors attached to your lens, and they are quite large, and the longer the lens, the more distotion and the lower the F.stop you will have to use.

    hope this helps
     
  3. Garbz

    Garbz No longer a newbie, moving up!

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    I don't think you can actually stack magnification filters. A free way to do wide angles if your subjects don't move is to make panoramas. There are plenty of free stitching programs available to get seamless results. Mind you getting the world to hold still is somewhat of a challenge.
     
  4. gryphonslair99

    gryphonslair99 Been spending a lot of time on here!

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    Jeff,

    Just a little clarification on your 18-50mm lens. It does not matter what camera you put that lens on, the focal length of that lens is 18-50mm whether it is on a 35mm film camera, a FF DSLR or a crop body DSLR, that lens still has a focal length of 18-50mm. With a crop body camera, (smaller sensor) you sensor is only seeing the approximate field of view of a 26-80mm lens. That is a crop of the field of view not a change in focal length. There is a difference. While it may seem like a small thing, different focal lengths have different
    [FONT=&quot]characteristics[/FONT]. Those [FONT=&quot]characteristics do not change because of the sensor size, they remain constant. [/FONT]
     
  5. JeffEmbracedDC

    JeffEmbracedDC TPF Noob!

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    Gotchya. That makes sense. And yeah you're definitely right. It doesn't change the focal length, it just crops. I imagine one of the characteristics you speak of is barrel distortion? Although, I'm probably way off. After all I've got the "noob" title under my name and I'm posting in the Beginners Place..

    So anyway, I have my 18mm (about 90 degrees) lens but it gets cropped closer to a 28ishmm (65 degrees). What wide adapter do I need to get to look more like a true 18mm lens? I'm not exactly sure what the "x" relates to when a wide adapter is labeled "0.45x". I assume it means it increases the angle by 45% which would make a 65 degree lens look more like a 97.5 degree lens which is close to 16mm? If that's the case that would make me very happy.

    Thanks for all of your help, guys!

    -Jeff
     
  6. WDodd

    WDodd TPF Noob!

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    A 0.45x adapter would make your focal length appear to be around 13mm. (18mm x 0.45 adapter x 1.6 crop factor = 12.98 or something)
     
  7. JeffEmbracedDC

    JeffEmbracedDC TPF Noob!

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    Thanks, guys!

    I know it will cause a reduction in sharpness and quality. Hopefully it won't be terrible. I'm gonna pick up a 0.45x adapter and see how it does. Thanks for the input, guys!

    -Jeff
     
  8. jstuedle

    jstuedle No longer a newbie, moving up!

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    My kids gave me one of these things for a B-Day present a while back. It sucks! The quality of the image is not just marginal, it is terrible! Bad, Really bad! I have never taken a pic with it other than a few test shots and I hate it. But because it was a gift, it sits on a shelf in the lens lock-up. Maybe they are better now, mine is about 7 years old, but I wouldn't get my hopes up too very high.
     
  9. JeffEmbracedDC

    JeffEmbracedDC TPF Noob!

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    I appreciate the input.

    I had one of these a while back for my Canon G5 and it worked very well..

    Any idea off hand what brand yours is? The canon seemed to be o-k quality...

    -Jeff
     
  10. JeffEmbracedDC

    JeffEmbracedDC TPF Noob!

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    This is the wide converter I had before that seemed to work well...

    [ame]http://www.amazon.com/Canon-WCDC58N-Converter-Adapter-Digital/dp/B00007JDRW[/ame]

    58mm rear threads

    -Jeff
     

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