Dear all, I have gathered some lenses questions for my nex-f3 if someone knows the answer please feel free to help me 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? 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) 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. 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
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.
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.
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
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
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.
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 -
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.
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?
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
Which is why life would be simpler if lens specs focused on FOV rather than focal length. Degrees is degrees.
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.
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
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.
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.
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.
