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Using the 20mm prime lens (newbie questions)

Discussion in 'Native Lenses' started by dabbler, Apr 19, 2011.

  1. dabbler

    dabbler Mu-43 Regular

    131
    Feb 5, 2011
    Hello all, I've just got my very first interchangeable lens camera, the GF1 with the 20mm kit! I've been trying to find out about the lens, but understandably most of what I've found talks about technical aspects of lens quality and assumes its readers will know how to use the thing! Sadly I don't yet, and so I was wondering if anyone here could help with two queries I have about how to use the lens?

    Firstly, I've read Bryan Peterson's 'Understanding Exposure', and he recommends using the lens at a very wide aperture for subject isolation pics, f8 or f11 for objects at the same focal length and f22 for compositions where you want both foreground and background to be sharp. On 'A' mode I can only get the GF1 down to f16, however. I'm wondering if the smaller crop of the 4/3 sensor affects which aperture settings produce these results? If so, which settings are equivalent to Peterson's f8/11 or f22 on a 4/3 sensor?

    Secondly, the lens says its focussing distance is from 0.2m to 'infinity'. Now, obviously 'infinity' can't actually mean infinity; at what distance does it decide the focussing distance is 'infinity', and what are the effects of this on depth of field? I've been surprised that the camera always seems to want to shoot at f1.7 unless I specifically tell it not to, so it seems an important thing to know!

    I hope you can help me!
     
  2. miha171

    miha171 Mu-43 Rookie

    10
    Mar 24, 2011
    Ljubljana, Slovenia
    Don't use any lens on micro 4/3 camera at f/22! I rarely go over f/11..
    If you want as much in focus as you can, than go to f/11 but not more. 20mm will give you enough focus at f/11.
    As for subjekt isolation, you will achieve this by using as big aperture as you can, in the case of Panasonic 20mm, this is f/1.7.
    Remember, big apertures are f/1,4, f/1,7, f/2.. and small apertures are f/8, f/11 and so on.
    Try shooting something with diferent apertures and you will see how it affects background focus on your shots. Isolation of a subject means the background is blurry.

    I would definitely suggest reading the whole manual (twice!). Trust me, it's important.
    As to you other two questions, I could try to explain, but I'm sure someone else will do it much better (same could be true for the first question :) ).
    You probably have the camera set to aperture mode, try auto. It will serve you well until you learn more..

    Hope this helps a bit,

    Cheers!
     
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  3. miha171

    miha171 Mu-43 Rookie

    10
    Mar 24, 2011
    Ljubljana, Slovenia
    And another thing about aperture. I don't know Bryan Peterson but I suppose he's talking about full frame cameras, which have sensors that are four times bigger than micro 4/3.
    I won't go into tehnical stuff but basicaly the lenses on those cameras give much more shallow depth of focus and use less open apertures than micro 4/3 for the same effect.
    40mm f/8 on full frame camera gives the same field of view and focus depth as 20mm f/4 on micro 4/3.
     
  4. MichaelShea

    MichaelShea Mu-43 Regular

    108
    Jan 27, 2011
    Algarve, Portugal
    You will not get the best image quality out of any M4/3 lens by using apertures smaller than f8. Almost all of them perform at their best somewhere around f4 or f5.6. At f16 virtually nothing will be sharp even if it's in focus. Depth of field is not simply about aperture, but also the focal length of the lens you're using. You're correct that the aperture numbers need to be revised to take account of the M4/3 sensor in the camera. F5.6 is roughly the M4/3 equivalent of f8 with a full frame sensor. My advice with that lens is to choose f4 or f5.6 as your default setting outdoors and see how you get on.
     
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  5. GingerCat

    GingerCat Mu-43 Regular

    26
    Apr 16, 2011
    Wow, I'm moving to m4/3 from a DSLR and hadn't realised things would be so different. Brian Peterson was my favourite book while learning to drive my 30D; if that no longer applies, who should I be reading now?
     
  6. Pelao

    Pelao Mu-43 Top Veteran

    959
    Feb 3, 2010
    Ontario, Canada

    From my perspective I would never use a default setting. For me the setting depends upon what I want from the final image - much as the OP was stating. So while lenses do indeed have apertures at which their performance is 'better', to me that information is less useful than selecting a setting for the best results that I need for any given image.
     
  7. MichaelShea

    MichaelShea Mu-43 Regular

    108
    Jan 27, 2011
    Algarve, Portugal
    That's very creative thinking Pelao, but your perspective isn't that of a beginner, with the system, the camera, or the lens.
     
  8. mzd

    mzd Mu-43 Veteran

    241
    Nov 30, 2010
    Wisconsin
    I'm sure much of what Brian Peterson says (i.e. the basic rules of photography) does apply, just some of the specific numbers will be different for m4/3 due to the cropped sensor. But once you translate the numbers to their m4/3 variants, all the basic rules apply.
    And yes, the GF1 does tend to pick the large apertures (f1.7) more often than not if you let it. The 20mm is a great lens inside and in low light and shooting with large apertures lets in more light so you can use lower ISO settings, greatly reducing visible noise. But, as mentioned, the lens does very well at f4 to f8, especially outside when there is more light.
    I have found this lens really shines when you are relatively close to your subject; within 8-10 feet and closer.
     
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  9. iliakoltsov

    iliakoltsov Mu-43 Regular

    195
    Aug 7, 2010
    Paris
    I agree for me it depends on the type of shooting i am doing , sometimes i end up closing to f16 with flash. really the best is to try and see by yourself , but i do agree that after f8 you start getting strange effects ( diffraction) especially visible on manual lenses but this gives you ground for creativity. :) the best way to learn is to have fun with it , and then you see what works what doesn't. I cannot comment on the 20mm as i do not own it , but the best way is to try and see what works .
     
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  10. kevinparis

    kevinparis Cantankerous Scotsman

    Feb 12, 2010
    Gent, Belgium
    I am guessing you are maybe shooting on P or Program mode and you are shooting in places with either the ISO too low or there is not enough light, so the camera is maxing out the lens aperture so as to keep the shutter speed as fast as possible.

    with the 20mm lens, as a general rule you should be shooting at around AT LEAST 1/50th of a second in order to minimize camera shake.


    there was an old rule of thumb for 35mm film cameras that said the slowest shutter speed you could safely hand hold was 1/focal length.

    With micro 4/3, because of the smaller sensor that gets revised to 1/(2*focal length)

    so for the 20mm that is 1/(2*20) or 1/40 of a sec

    K
     
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  11. iliakoltsov

    iliakoltsov Mu-43 Regular

    195
    Aug 7, 2010
    Paris
    Kevin you can get away with just 1/focal length .
     
  12. Pelao

    Pelao Mu-43 Top Veteran

    959
    Feb 3, 2010
    Ontario, Canada
    Fair enough - although the OP was mentioning the different results that could be obtained through changes in aperture. Miha171's suggestion makes a lot of sense to me:

    The OP seems to want to learn.

    Of course there is no right or wrong approach, and the advice keeps flowing so I am certain the OP will find what is relevant to their needs.
     
  13. kevinparis

    kevinparis Cantankerous Scotsman

    Feb 12, 2010
    Gent, Belgium
    yeah you can get away with it - if you know what you are doing - but factor in a newbie, holding the camera at arms length and the fact that the 20mm has no image stabilisation, and its probably better to aim for 2x focal length.


    I know from my own experience that I lose more shots from camera shake than any other factor - I posted what I did to encourge newbies to be aware of the effect that shutter speed can have on an image, and to give them a ballpark figure they should be aiming at

    K
     
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  14. Pelao

    Pelao Mu-43 Top Veteran

    959
    Feb 3, 2010
    Ontario, Canada
    Similar experience here. I can get away with slower shutter speed, but only when bracing the camera (EVF or strap) and then it is not always effective. I suppose it also depends upon what you find acceptable. Where possible I prefer 1/40 and up with the 20.
     
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  15. Alanroseman

    Alanroseman Super Moderator Emeritus

    Dec 21, 2010
    New England
    I'm sure you've seen this thread....

    Hi Dabbler,

    You've generated some good discussion here, from some very experienced folks. It's one of the things we do best here, offer information.... often at maximum verbosity..:smile:

    Try to take in as much as possible, then ask again if you have to.
    Remember, the cost of film for your GF1 / 20 is really really low... so shoot shoot shoot...

    Make the same image at different f stops by increasing or decreasing the shutter speed, or ISO settings.... or by using A mode and changing the actual aperture itself.. You'll see the difference.

    While your at it... poke around here, and see if it answers any questions.... or generates even more.

    https://www.mu-43.com/f80/panasonic-20mm-f-1-7-image-thread-298/

    In the meantime, it's doubtful you'll visit anywhere and get more / better info than you'll find here..

    Cheers, Alan
     
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  16. fin azvandi

    fin azvandi Mu-43 All-Pro

    Mar 12, 2011
    South Bend, IN
    Thanks for this question and the helpful responses. I knew that the effective (35mm equivalent) focal length of a lens on m4/3 is double, but didn't realize we need to mentally convert apertures as well. That kind of limits the range of useful apertures on legacy lenses, doesn't it, since many of them are not very sharp wide open?

    On the Hexanon 40/1.8 for example, this would imply that the recommended apertures are only 2.8, 4, 5.6, and 8 (maybe 11)?
     
  17. GaryAyala

    GaryAyala Mu-43 Legend

    Jan 2, 2011
    SoCal
    Without any mirror slap one can easily shoot at shutter speeds lower than the Rule-of-Thumb ... but I suggest doing so for people who have already some practice with low shutter shooting techniques.

    The smallest aperture for the Pany 20mm, 1.7 is f/16.

    And yes, infinity is pretty much infinity, (in human terms and standards and not getting confusingly technical). Shooting a hilltop ... say 100 yards away with the Moon behind the hilltop and the lens set at infinity ... both the hilltop and the Moon will be in focus.

    Gary
     
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  18. dabbler

    dabbler Mu-43 Regular

    131
    Feb 5, 2011
    Thanks for all your responses! I'm doing quite a bit of experimentation, but it's really useful to have all these pointers to use as jumping-off points, especially as the experimentation is interspersed with events I would like to record. Any acceleration of the learning curve is therefore very welcome!

    Thanks again, Dabbler
     
  19. Amin Sabet

    Amin Sabet Administrator

    Apr 10, 2009
    Boston, MA (USA)
    I've been doing this for a while, holding the camera to my eye, and I still prefer 2x focal length :redface: :smile:.
     
  20. Brianetta

    Brianetta Mu-43 Veteran

    438
    Sep 5, 2010
    North East England
    Brian Ronald
    Infinity means infinity, in this case. Imagine, if you will, that you have two arrows pointing at something. The angle between those arrows is indicative of the distance to that something. As that something moves away, the arrows move towards parallel.

    Your lens is a little like that. When you focus, you're changing the angle between those metaphorical arrows. When you focus on infinity, they are parallel.

    It's actually possible to focus beyond infinity. Of course, rudimentary maths tells you that nothing's that far from the lens. Correct; nothing's in sharp focus, either. Your arrows are pointing away from each other.
     
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