1. Reminder: Please use our affiliate links for holiday shopping!

Lens confusion

Discussion in 'Panasonic Cameras' started by Phil66, Dec 27, 2011.

  1. Phil66

    Phil66 Mu-43 Regular

    130
    Dec 27, 2011
    Ello all,

    I'm probably being a numpty, I've never really had a proper camera except for a Minolta SLR back in the day which I got rid of because I didn't understand how to use it and wasted loads of film.

    I watched this video Lumix G3 Review - YouTube and he puts a 70-200 lens on the G3 from 35mm camera. He says that it then becomes a 140-400 which I sort of understand. I then read this this comment on a forum "What differs for m43 and FF (Full frame 35mm camera image size) is that a 20mm focal length lens on m43 will capture the same angle of view as a 40mm lens on a FF camera. Those of us brought up on 35mm photography in the film era simply have to double the focal length of a m43 lens to translate it into angle of view equivalence of those former 35mm film lenses we used.". Now to me that seems opposite to what the guy on the video is saying.
    The guy one the video says that a lens off a 35mm camera that is put onto a m43 gets double the focal length. The guy on the forum is saying that a 20mm M43 lens is equivalent to a 40mm lens from a 35mm. That seems to me to be opposite to they guy on the video.

    Can someone please explain?:confused:

    Thanks.

    Phil
     
  2. dannat

    dannat Mu-43 Regular

    174
    May 2, 2010
    Melbourne Australia
    The focal length doesn't increase, 100mm is 100mm & the camera doesn't magically double the length. The second guy ir correct, the small sensor on mu4/3 does not cover the same area as a FF or film camera, in fact it covers half of the size. Imagine you took a pic with full frame close up with a 30cm ruler, the ff would get the whole 30cm, the mu4/3 would see 15cm (which they say is the equivalent size view of doubling the focal length of the FF).so at any given focal length on mu4/3 the full frame would be double the foal length to show you the same area in the final image
     
  3. Ned

    Ned Mu-43 Legend

    Jul 18, 2010
    Alberta, Canada
    It's saying the same thing. :) You double the focal length of the m4/3 lens to get the equivalent field of view as you would see on 35mm film. ie, the 70-200mm gives the FOV of a 140-400mm.

    Of course, the problem with that is that 35mm film is 3:2 aspect whereas m4/3 is 4:3 aspect. That means that the view you get will actually not look anything the same as a 140-400mm on 35mm film or Full Frame digital. Which of course blows the whole concept of "equivalency" out of the water, lol.

    The closest you'd get would be to multiply the focal length by 1.7x then crop off the long edges.

    Here's an example...

    Full Frame View:
    sensor-size_full_frame.
    APS-C sensor (1.6x crop):
    sensor-size_aps-c.
    Four-Thirds sensor:
    sensor-size_four-thirds.

    As you can see, the 1.6x crop (which is the same aspect ratio and therefore an accurate figure) looks almost the same as the Four-Thirds image which we call a "2x" crop, except that the image is cropped at the bee's knees. ;)
     
  4. Phil66

    Phil66 Mu-43 Regular

    130
    Dec 27, 2011
    Thanks for all that. I find it all a bit confusing at the moment.
    I'm upgrading from a Canon Ixus 800 IS. I'm almost 100% sure I'm buying the right camera for me especially if I buy the 20mm Pancake lens for use indoors at the many National Trust properties we visit.
    I've always like the idea of an SLR but the size has always put me off. If anyone has any other suggestions they would be gratefully appreciated.
    Thanks
    Phil
     
  5. dhazeghi

    dhazeghi Mu-43 Hall of Famer

    Aug 6, 2010
    San Jose, CA
    Dara
    If you're planning on going from a camera with a zoom lens (like the Ixus 800) to using a fixed lens (like the 20/1.7 pancake), make sure the focal length suits your style/needs. Especially indoors, it's hard to 'zoom with your feet'.

    DH
     
  6. Markb

    Markb Mu-43 Top Veteran

    532
    Jun 9, 2011
    Kent, UK
    Mark
    Ned has explained crop factor beautifully so I'll concentrate on len usage.

    I'd advise getting a zoom to begin with (the Olympus and Panasonic kit lenses are fine, very good in fact). Use it for a bit and then work out which focal length(s) suit you best. If you do everything at the short end you want the 14 or 17mm. At the long end and still cropping? You need a telezoom like the 45-200 or 40-150. If you do everything around the middle of the range go for the 20 or 25mm. Do try to move around the subject though rather than just whizzing through the zoom range. It'll teach you more of what you can expect if you make the move to primes. If it does everything you need thank your lucky stars and be happy :smile:

    You'll also know if you're lacking anything wider or longer when you reflect on the ones that got away.
     
  7. Phil66

    Phil66 Mu-43 Regular

    130
    Dec 27, 2011
    I was going to get the G3 with the it zoom which is 14-45 (I think) and I was going to buy the 20mm pancake for mainly indoor use as it is supposed to be very good in low light. See reviews here Amazon.co.uk: Customer Reviews: Panasonic Lumix G 20mm/F1.7 Pancake Lens
    I would be willing to look at other cameras but this really does seem to be the one. The GH2 has more features but it is a little larger.
    Do you think the pancake will be good at relatively low ISO's (400 or lower) indoors at properties like stately homes?
    Phil
     
  8. Markb

    Markb Mu-43 Top Veteran

    532
    Jun 9, 2011
    Kent, UK
    Mark
    I think the 20mm would be excellent in stately homes and the like. You won't have any image stabilisation though if you do need slower shutter speeds.
     
  9. Phil66

    Phil66 Mu-43 Regular

    130
    Dec 27, 2011
    Would the Panasonic 14mm f2.5 Lumix G Lens be a better option? I was thinking I would be able to get more of the room in the frame with it?

    Phil
     
  10. meyerweb

    meyerweb Mu-43 Hall of Famer

    Sep 5, 2011
    I think the answer is "maybe." Yes, it has a wider angle of view and you will be able to get more in the frame. The downside is that it's a stop slower, so you'll need to use a higher ISO or lower shutter speed in any given light.

    Since you're starting with the 14-42 kit lens, I'd suggest going to some of your properties with that lens, and see if 20mm is wide enough for your needs, or if 14mm will work better.
     
  11. Phil66

    Phil66 Mu-43 Regular

    130
    Dec 27, 2011
    I'm all confused. You say it's a stop slower, as it's just over 30% shorter how much difference would this make? I'm new to all this and only get a little bit about f stops and such like so please bear with me.

    Phil
     
  12. LovinTheEP2

    LovinTheEP2 Mu-43 Top Veteran

    619
    Feb 15, 2011
    Toronto
    Honestly.... people make too much of the crop factor issue on non full frame sensors.

    17mm is 17mm focal length period. The length of the lens doesn`t change irregardless of sensor size ie FOV crop.

    Doesn`t matter if you are using m43s designed lens or legacy glass... a millimeter is a millimeter is a millimeter. 17mm m43 or a FF is still 17mm. It`s only what you see on the camera screen or VF that is different and equivalency is just a very rough approximation.

    The equivalency issue is really only an issue for PROs who who have taken photos for years with either film or full frame dSLRs and are looking for a smaller form factor camera and are used to shooting a particular way or scene and want to reproduce similar images in crop factor camera.

    So if you are used to shooting with a Canon 1Dx and 35mm or a 135mm lens, going to a m43s body can be an issue if you want the same FOV as that is how you are comfortable shooting previously 1,000s of exposures.

    For a person coming from a P&S, it's a non issue. I wouldn't even concern myself with it.

    Its also a bit important to review sites when comparing different sized sensors and they want to show how 2 cameras compare to one another and want a FOV that is very close to one another.

    ie Comparing a Olympus EP3 with a 45mm lens to a Sony NEX5 or NEX7. Some people like to see a very similar FOV. There are pros and cons to such review setups. I personally perfer each camera to be treated on its own with each camera and its best lens offering and pixel peep at 100% to see IQ then worrying about equivalent FOV.

    Just understand that on a micro 43rds body a focal length lens of:

    17mm or less is considered wide angle. Good for indoors and landscape work. (or 35mm FOVequivalency which it actually isnt)

    20-25mm is considered normal. 25mm end is a bit long for indoor shots. (or 50mm FOV equivalency which it actually isnt) - Good all purpose range.

    45mm+ is a good portrait length in m43s. (or 90mm FOV equivalency which it actually isn`t) Good for subject isolation and not get any distortions etc. Yields a very pleasing image of an object.

    60mm+ is telephoto (or 120mm FOV equivalency long range zoom)
     
  13. LovinTheEP2

    LovinTheEP2 Mu-43 Top Veteran

    619
    Feb 15, 2011
    Toronto
    A Light Stop isn`t a function of focal length. The amount of light a lens lets in is not a function of its length but its aperature in relation to its length ie F.

    ie 0.95, 1.4, 1.7, 2.0, 2.8 ... 5.6etc.

    The smaller the F number, the bigger the aperature and hence more light gets in. it is actually a fraction so its actually 1/0.95 vs. 1/2.8 vs. 1/5.6(smaller and smaller amount of light reachs the sensor)

    Basically, the more light your lens lets in (F) the faster you can take an image (seconds) to avoid motion blur and-or allows lower ISO setting so less noise etc. For low light conditions and m43s not being great at ISO performance and DR.. a fast lens really helps in keeping as much DR and keep noise to a minimum as you can save yourself 1-2 maybe even 3 ISO stop if you have a fast lens like the 20/1.7 and IBIS.

    An exposure (or picture) is based on 3 items:

    Aperature
    Speed
    ISO

    F2.8 1/30s Iso 400 = F2.8 1/120s ISO 1600

    But the 2nd exposure setting taken with a faster shutter speed (1/120th) would yield an image with potentially less blur as 1/30th for some isnt steady enough but would have more noise and a drop in dynamic range as a result as you would need to increase the ISO 2 fold (--> 800 --> 1600) to make up for the 2 stop increase in speed of the shutter cutting light by 2 fold (1/30s --> 1/60th --> 1/120s. So if you had a fast lens by 1 or 2 stops, you could get the ISO down to 800 or 400 reduce the noise and improve the exposures dynamic range. That is overly simplistic example as you could also change the aperature as well.

    Heres is a decent link explain the exposure triangle and F-stops etc.

    http://www.cambridgeincolour.com/tutorials/camera-exposure.htm
     
  14. Phil66

    Phil66 Mu-43 Regular

    130
    Dec 27, 2011
    Thanks, that was all very interesting.

    I knew F stops aren't a function of focal length, I just thought that if the lens has a shorter focal length by a bit more than a third then when you work out the aperture diameter there wouldn't be that much in it. I might be talking a load of bs but I do find it confusing. It's probably one of those things that when the penny drops we say "Doh! why didn't I get it???"

    Thanks again and sorry to be a pain but I really want to be sure I'm getting the right thing.

    Phil
     
  15. The 14mm may be one stop slower than the 20mm, but the shorter focal length should make it possible to hand-hold it at a slightly slower shutter speed.
     
  16. Markb

    Markb Mu-43 Top Veteran

    532
    Jun 9, 2011
    Kent, UK
    Mark
    The old rule of minimum shutter speed = 1/(35mm equivalent) focal length would give you a minimum shutter speed for the 14mm of about 1/30s. For the 20mm about 1/40s. About 1/3 stop difference here and the 14mm is still a stop slower. The 14mm end of a Panasonic kit zoom is about a stop slower than the 14mm but would benefit from OIS pretty much wiping out the speed difference with regard to camera shake.
     
  17. LovinTheEP2

    LovinTheEP2 Mu-43 Top Veteran

    619
    Feb 15, 2011
    Toronto
    Aperature - F stop link

    F stop = Focal Length / Diameter of pupil

    So even though the focal length of the 14mm is 6mm shorter then the 20mm, it doesn't change the F-number as the diameter is different as well.

    It's generally accepted that 1/focal length (35mm equiv) you are able to handhold a steady shot. 1/14th (1/28) vs. 1/20th (1/40th).. it's about a 1/2 stop difference in speed to handhold a steady shot making a greater chance you get more unblurred shots using the 14mm. So you gain a 1/2 stop in shutter speed but lose 1 stop in light for a net loss of 1/2 stop.

    But you also have to take into consideration focusing speed and the 14mm is faster then 20mm and doesn't hunt as much so once again more likely to get a steady shot if your hand holding and waiting for the focus to lock.

    And that's at maximum F (ie 1.7 vs 2.5)..where most lens are a bit soft. For maximum sharpness, you will probably have to stop down a bit to get the sweet spot for each and in that case, the difference is probably gonna be greater then 1/2stop.

    For low light where sharpness is less of a concern and controlling noise is probably more of an importance, the 14 to 20 is probably a wash and more about FOV perference. The F advantage of the 20 probably loses out to the 14mm faster autofocus and shorter focal easier to handhold a shot.

    Granted, I havent had the opportunity to play with the 14mm so thats based on user reports that I have read of real world users and the limited time I've spent with the 20.

    The 14mm is pretty wide and you may find it difficult to take photos of people or objects in close proximity without getting some perspective distortion. Just some food for thought.
     
  18. meyerweb

    meyerweb Mu-43 Hall of Famer

    Sep 5, 2011
    Assuming your subject isn't moving.
     
  19. But surely there's no fast movements inside stately homes? :wink: