Need help for the correct lens

Discussion in 'Photography Equipment & Products' started by suh00ail00, Aug 13, 2009.

  1. suh00ail00

    suh00ail00 TPF Noob!

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    Hello there, I need you guys to help me out here to find the correct lens.
    The image below is the steup for me to shoot the gemstones. And now I need the correct lens that can help me to get the img of the gemstone below at a good quality.
    [​IMG]

    This is a specially designed box that I bought and has the perfect lighting and other stuffs but the problem is. I cannot get a close shot at the gemstone below. If anyone can help me with the correct lens for my Canon 500D it will be great

    Here is the shot of the image below that I want it to be like. I need that clarity. I haven't acheived this great quality.

    The lens I have now is a normal 18-55mm canon lens that comes with the camera. Can anyone help me with this?

    [​IMG]
     
  2. Overread

    Overread has a hat around here somewhere Staff Member Supporting Member

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    What you need is a macro lens for working at those distances. If you are just sticking with gemstones and not going into insects then there are several you can consider, which are not at the higher end of the budget;

    Canon EFS 60mm macro - a very good macro lens, its weakness is that it is EFS only (It won't fit on a 5D fullframe camera) Of course if a crop sensor camera is all you are going to use its no limitation

    Sigma 70mm macro - like the 60mm its a very sharp and good quality lens, but its also fullframe compatable.

    Tamron 60mm - not released yet - not out yet and with the same limitation as the canon, this macro lens however does sport internal focusing (it does not extend as you focus, whilst the other two do) and it has a longer working distance as well.

    Provided there is space in the ringlight you have setup to allow the lens to move through it with ease then the Canon or the Sigma lens should be more than enough for your needs. However since you have the metalic dome to consider you might find that you need to test out the lens in a shop with your setup first as you might need a longer working distance offered by a longer focal length macro lens.
     
  3. Garbz

    Garbz No longer a newbie, moving up!

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    You need a "macro" lens. These are often speced as a reproduction ratio. A lens that is 1:1 would project a 1cm wide object 1cm across the sensor plane of the camera. Your sensor has a certain size (APS-C 22.3 x 14.9mm) and then it's up to the resolution of your screen.

    Suppose then for instance you have a 22" wide image at the full resolution of your sensor and you want 20" of that filled up with your gem which in actual size is 10mm wide, you would need a lens that goes to 2:1. If you want a 5" wide image you can deal with a 1:2. Your current lens I believe has a 1:3ish ratio.

    1:1 are normal modern proper macros. But canon make a closer one still which zooms from 1:1 to 5:1 I believe. I'll let a Canon user jump in and correct me here.
     
  4. Overread

    Overread has a hat around here somewhere Staff Member Supporting Member

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    Ok you know the math more than me - :)
    Canon do make a lens capable of zooming up to 5:1 magnification, though you would need to alter the lighting setup - since as you go beyond around 2:1 you need additional lighting to illuminate the subject. Infact since you are shooting into a dome I would think you would need additional lighting as standard for this setup - the Canon twinlights are often used for this feature as they have a flash on function where they provid this needed light - you can also expoeriment with LED bulb torches with flexi arms.

    The Canon MPE65mm is the macro lens you need for the greater magnifcaions but be warned its a very specialist lens as it will only do macro work.

    As an alternative you can use teleconverters with hte sigma 70mm macro (sigma brand teleconverters that is) and a 2*TC would give you 2:1 magnifcation from the 70mm macro. However generally speaking the MPE65mm gets the best image quality when going beyond 1:1 magnifcation
     
  5. suh00ail00

    suh00ail00 TPF Noob!

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    i think i understand what you guys are saying. and i guess a 2:1 is enough for the magnification so which lens will be good for this?
     
  6. Garbz

    Garbz No longer a newbie, moving up!

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    Just a thought, his subject isn't going anywhere. Extra light is not needed as much as it is available already. Simply use a longer exposure for a continuous light source, or fire the flash twice for a strobe.

    I take it from the diagram the entire thing is setup quite rigidly.
     
  7. Josh66

    Josh66 Been spending a lot of time on here!

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    Beyond 1:1, you're looking at either the MP-E 65 (1:1 - 5:1), or a macro coupler or something...

    I don't know of any macro lenses (other than the MP-E 65) the gets closer than 1:1...


    I don't think you really need more than 1:1 though... the 100mm macro (Canon) would be perfect for this. 105mm if you shoot Nikon.
     
  8. Josh66

    Josh66 Been spending a lot of time on here!

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    Just a thought...

    The MP-E 65 will most likely NOT work with your dome. It would have to be inside the dome to attain focus...
     
  9. suh00ail00

    suh00ail00 TPF Noob!

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    ok cool. I guess i will be going for the 100mm canon, just a quick question is can i shoot with a far distance of 35cm? because when it is 100mm it is going to be fixed Im just worried the distance will be too much or too less making it out of focus. Let me know about it too.
     
  10. Overread

    Overread has a hat around here somewhere Staff Member Supporting Member

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    Suh00ail00 I think your metal dome is your major limiting factor here - I would suggest trying to abandon it for the moment, get a macro lens (whichever you feel is right and fits your budget) and they try shooting. Heck maybe see if your local store can get a few in for you to test with your setup.
    It might be that you do need to modify your dome assembly in order to get the magnifcation from the correct lens as you desire. Placing the dome as a limiter first is going to give you problems I feel
     
  11. Mike_E

    Mike_E No longer a newbie, moving up!

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    Extension tubes are cheap.
     
  12. Dao

    Dao No longer a newbie, moving up!

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    Based on the setup above, I think the dome can be modified to a collapsible dome made of:

    - a series of metal wire rings (different size). Smallest rings at the top and rings get bigger towards the bottom.
    - a reflective cloth type material (or white) such as the one used in umbrella.

    Make the reflective / white material so that it looks like a dome. And then use the wire rings to support it. Position the rings horizontally and make them about 1 inch apart. When it hang the dome from the top, due to gravity, the dome will expand and the bottom part will reach the table top.

    So the distance between the camera and the product can be adjust with the dome in place.

    Of course, this is just my thought and I never done that before and do not know if it will work.



    And by the way, I really like my Canon 100mm macro lens. Although the one I have is the older version (non-usm), but it still a very sharp lens.
     

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