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Few Lens questions

Discussion in 'Sony Alpha E-Mount Lenses' started by alaios, Jul 11, 2013.

  1. alaios

    alaios TalkEmount All-Pro

    Jan 11, 2013
    Düsseldorf
    Alex
    Dear all,
    I have gathered some lenses questions for my nex-f3 if someone knows the answer please feel free to help me

    1. The crop factor is 1.5x for nex. That means multiplying the focal length of an adapted lens by 1.5. Does it also the same for the nex lenses? The focal length written there should be also multiplied by 1.5 or is already taken into account?
    2. sigma 19mm lens hood. I have read that the 19mm comes with a hood. Is that right? Is there any hood I can buy for the 30mm as well (it did find any inside the box of the 30mm)
    3. I was looking for the nex 16mm lens but it costs almost two times the sigma 19mm. Are there other alternatives for wide apertures and fish-eye converters for adapted lenses? I feel tempted trying to fish-eye shoots but the cost of the nex 16mm is way over of I can afford.
    4. Regarding the crop factor. What is also for compact digital cameras? Is the apperture what they right on their lens or not?

    I would like to thank you in advance for your help
    Regards
    Alex
     
  2. Poki

    Poki TalkEmount Hall of Famer

    Aug 30, 2011
    Austria
    1. Yes, all focal lengths need to be multiplied with the crop factor.
    2. Yep, comes with a hood. If you really want a hood for the 30mm, look if they sell the one that ships with the newer 30mm lens model separately.
    3. Most converters aren't good. But the Samyang 8mm (especially the newer, smaller f/2.8 version) is said to be great as a fisheye. As for ultra wide, there are no cheap options that are good. The Zeiss 12mm or the Sony 10-18mm obviously being the best choices here.
    4. Crop factor applies to all cameras except these with a 35mm sensor. So even medium format cameras have a crop factor, although a negative one (0.70 for example). You do this just to be able to compare lenses for different systems. The aperture is what 'they write on the lens' regarding light gathering capability, but must be multiplied with the crop factor to get the shallow depth of field comparable to a ff system.
     
  3. davect01

    davect01 Super Moderator

    Aug 20, 2011
    Fountain Hills, AZ
    Dave
    Just a couple more thoughts

    1- Yup. This is for comparisons to the same lens on a full frame camera.
    2- I bought an aftermarket hood on Ebay for about $8.00.
    3- Don't use any personally.
    4- Again for comparing to full frame cameras.
     
  4. alaios

    alaios TalkEmount All-Pro

    Jan 11, 2013
    Düsseldorf
    Alex
    2. Sadly cant find any on ebay. I am searching as sigma 30mm hood...
     
  5. Amamba

    Amamba TalkEmount All-Pro

    Apr 13, 2013
    SE MI
    The problem with hoods is, unless you know the exact dimension the particular lens requires, they are the waste of money as they would be either too short and not providing enough flare protection, or too long causing vignetting.

    I don't think Sigma 30 is prone to flare, anyway.

    Sent from my Nexus 7 using Tapatalk 2
     
  6. quezra

    quezra TalkEmount Top Veteran

    916
    Aug 22, 2012
    The original Sigma 30mm does not come with a bayonet to attach a hood like the 19mm. I think the new one does though I'm not 100%

    Sent from my Nexus 7 using Tapatalk 2
     
  7. addieleman

    addieleman Passionate amateur

    Nov 13, 2012
    Netherlands
    Ad Dieleman
    Alex, look for "lens hood 46mm" on eBay, you'll get a lot of hits. I have no hesitation to order one from China but you may have to be patient, depending on the supplier it can take weeks before it arrives. Also take care that the price of the hood doesn't exceed € 22 when you order from outside the EU; not likely for such a hood anyway.

    I use one that looks a lot like this one and it works fine for me; I prefer a screw-on lens hood because I can put a polarizer on the lens, then the hood and this way I can easily turn the polarizer. Using a polarizer with a bayonet-type lens hood like that of the Sigma 19/2.8 is a PITA.
     
  8. -et-

    -et- TalkEmount Veteran

    205
    Jan 26, 2013
    Southern California
    Tom
    For the Sigma 30mm lens, use a hood that screws in to the thread on the lens that is used for filter attachment. I do not have the lens with me at the moment, so I am not positive about the correct thread size, but I believe that it is 46mm. Check the label on the lens before you look for a hood.

    - Tom -
     
  9. alaios

    alaios TalkEmount All-Pro

    Jan 11, 2013
    Düsseldorf
    Alex
    hmm thanks for the suggestions. The samyang is around 190dollars but I guess with that money is better if I go for the sony 16mm to have also image stabilization at hand.
     
  10. Poki

    Poki TalkEmount Hall of Famer

    Aug 30, 2011
    Austria
    The Sony 16mm is not stabilized.
     
  11. davect01

    davect01 Super Moderator

    Aug 20, 2011
    Fountain Hills, AZ
    Dave
    Yup. Plenty available, take your pic.
     
  12. alaios

    alaios TalkEmount All-Pro

    Jan 11, 2013
    Düsseldorf
    Alex
    I am correcting my point 4.

    4. Regarding the crop factor. What is also for compact digital cameras? MY digital camera, canon sx 220hs, has a lens 7-70mm. Should I apply also some crop factor too?
     
  13. Amamba

    Amamba TalkEmount All-Pro

    Apr 13, 2013
    SE MI
    What for ? The crop factor is only useful for comparing different systems, I.e. a 100mm lens on full frame provides the same field of view as 67mm on Nex (1.5), 63mm on Canon 60D (1.6), or 50mm on a MFT (2). Your PowerShot has a fixed lens, you get what you get. I think your camera has a crop of 5.6, so it's like 40-400 on full frame, but there's really nothing you can use this info for.

    Sent from my Nexus 7 using Tapatalk 2
     
  14. Bimjo

    Bimjo Super Moderator

    Oct 28, 2011
    Washington State
    Jim
    Which is why life would be simpler if lens specs focused on FOV rather than focal length. Degrees is degrees. ;)
     
  15. Amamba

    Amamba TalkEmount All-Pro

    Apr 13, 2013
    SE MI
    FOV of a lens is variable depending on the body. FL is fixed. 50mm lens may give different FOVs on different bodies but it remains 50mm.
     
  16. alaios

    alaios TalkEmount All-Pro

    Jan 11, 2013
    Düsseldorf
    Alex
    I think I mostly needed that to start getting the experience "50mm is how it looks that" Which I guess should be similar either in a compact or in any other camera.

    Sent from my PC using keyboard
     
  17. Bimjo

    Bimjo Super Moderator

    Oct 28, 2011
    Washington State
    Jim
    That's the point- the FOV changes on different bodies. So 50mm really doesn't convey what you're going to get on different cameras. If the FOV was listed for different sensors it would be much more useful info. If you consider P&S camera with tiny sensors what does 5.5mm to 12mm tell you in real world terms?

    Assuming you know the crop factor you can do the math and figure out the FOV. But why do math? Once you know what a 75 degree FOV looks like you can relate that to any camera.

    JMO, nothing says you have to agree. :)
     
  18. Poki

    Poki TalkEmount Hall of Famer

    Aug 30, 2011
    Austria
    Just a little addition: Two different 50mm lenses on the same body don't necessarily give you the exactly same FOV. First, the focal length often gets rounded - so a 50mm lens might well be a 48 or 52 in reality. Above that, even if the lenses are really 50mm from an engineering standpoint, the FOV changes with the amount of distortion and field curvature. That's also why fisheye lenses have a much larger FOV than the same focal length lenses without the fisheye distortion.
     
  19. Amamba

    Amamba TalkEmount All-Pro

    Apr 13, 2013
    SE MI
    Bimjo: for the same lens, they would have to list what, 4 FOV values. And keep adding if someone designs a sensor with a yet another crop factor. While the focal length of a lens is an independent physical characteristic.
     
  20. Poki

    Poki TalkEmount Hall of Famer

    Aug 30, 2011
    Austria
    You just need to tell the FOV of the sensor size the lens is designed for.