Zone focusing?

Discussion in 'Sony RX100 Forum' started by Tom K., Aug 17, 2013.

  1. Tom K.

    Tom K. SC Regular

    185
    Aug 17, 2013
    Connecticut.
    Tom
    I have been shooting a lot of street photography lately and I am hooked. I use the Sony RX100. I would love to be able to incorporate zone focusing with it as I shoot from the hip quite often as you can see in my Flickr gallery here: Flickr: Tom Kaszuba's Photostream

    Any thoughts, tips, advice or ideas are welcome.

    Thank you,
    Tom K.
     
  2. Ray Sachs

    Ray Sachs SC Legend

    Sep 21, 2010
    Not too far from Philly
    you should be able to figure it out...
    Welcome Tom.

    The good news is that what you're doing seems to be working pretty well. You're over the biggest hurdle, which is not being afraid to get close enough, and if you're using auto-focus, the camera seems to be getting it right a lot. I don't know how many out of focus shots you're leaving on the cutting room floor, but you've got a lot of nice sharp, in-focus, shots in your Flickr stream. That A-Rod shot is remarkably in focus - most cameras wouldn't pick up that the bat was actually a hypodermic needle! :cool:

    The bad news, however, is that as many things as the RX100 does well, zone focussing is something its not set up to do at all. The basic requirement for zone focussing is some sort of distance scale so you know the distance the camera is focussed at. From there, you just need to get hold of an online depth of field calculator and work out appropriate aperture/distance combinations that work for you in different lighting conditions. For example, at your widest lens setting (28mm equivalent), at f5.6 with focus set to six feet (about two meters), you're slightly past hyperfocal, so everything from 3 feet to infinity should be in pretty good focus. In lower light, at f3.5, everything from about 3.5 - 17 feet will be in focus, still a very useable "zone" of focus for street shooting. The problem is that the RX100 doesn't have any sort of distance scale, so there's no way to set this precisely.

    The easiest workaround is to just hold the camera about six feet above the ground (easy to estimate if you're about six feet tall) and focus on the ground, probably using auto-focus, and then quickly switch over to manual focus before the focus changes from that six foot spot. When I had the camera I remember there was one way to do this where the focus would lock right away, and another where it might re-adjust itself before you could get it locked down, but I don't recall those, so you'd have to figure that out. Another workaround is to just turn on the focus peaking aid, keep the camera in manual focus, and use the peaking indicators to see about what zone is in focus. This is not terribly precise but it should work reasonably well. I've had some problems trying this technique with a Nex (also no distance scale), but the depth of field on the RX100 should be wide enough that it should be somewhat more forgiving than the Nex... Its worth trying anyway.

    The bottom line is that what you're doing seems to be working, the RX100 is not set up to in any way encourage or enable zone focussing, but you can work around it if you really want to using one of the techniques mentioned above. Or you can keep doing what you're doing. Or you can get a different camera that gives you a distance scale...

    Good luck,

    -Ray
     
  3. serhan

    serhan SC All-Pro

    May 7, 2011
    NYC
    I trust quick af of RX100 but again I don't do that much street shooting also. 2 problems I found is slow opening speed for the lens which made me lost a shot and the min shutter speed which is 1/30 for RX100. So when the light are low, then I change to shutter priority, otherwise I get the motion blur from people or vibration from my hands...
     
  4. Armanius

    Armanius Bring Jack back!

    Jan 11, 2011
    Houston, Texas
    Jack
    Welcome Tom!!!
     
  5. Armanius

    Armanius Bring Jack back!

    Jan 11, 2011
    Houston, Texas
    Jack
    If I put a M lens on a m4/3 camera, the DOF scale on the lens can still be relied upon right? The DOF should stay the same regardless of the equivalent focal length that the lens becomes due to sensor size?
     
  6. Ray Sachs

    Ray Sachs SC Legend

    Sep 21, 2010
    Not too far from Philly
    you should be able to figure it out...
    Yeah, it should. I don't know if any of the flange distance stuff has any impact on that, but the actual focal length of the lens stays the same, as does the DOF, regardless of the equivalent focal length or field of view.

    -Ray
     
  7. porchard

    porchard SC Veteran

    344
    Feb 24, 2013
    Devon, UK
    Welcome to the forum.

    As stated above, it isn't possible to zone-focus on the RX100. It is, however, possible to "dummy" zone-focus by the following method.

    1. Make a note
    of the following data for calculating Hyperfocal Distance (HFD):-

    Focal length (effective)
    ..................... HFD (in metres)

    28mm ................................................. 10/Av
    35mm ................................................. 15/Av
    40mm ................................................. 20/Av
    50mm ................................................. 31/Av
    70mm ................................................. 61/Av
    85mm ................................................. 89/Av
    100mm ............................................... 123/Av


    2. Set the centre button to toggle between AF and MF (see user manual - page 130)


    3. Set desired focal length


    4. Set desired aperture (in Av mode)


    5. Point the camera at an object which is at the calculated HFD and focus (using AF)


    6. Toggle to MF and the focus distance is then locked until you either adjust it, or toggle back to AF.



    Note that the HFD calculations above have been rounded to provide integers for ease of use. Self-evidently, this method is a lot less convenient than using HFD on a manual lens, and also requires a good ability to estimate distance.

    It does take a couple of attempts to get comfortable with this method, but it does work. Hope it helps... good luck.:smile:
     
  8. flash

    flash SC Veteran

    372
    May 6, 2011
    Gordon
    Hmmmm. My DOF calculator doesn't agree with this statement.

    If the aperture, focal length and shooting distance distance stay the same (which they must in this case) then there is more the DOF with the smaller sensor at the same print size. So you'll need to add stops on the lens markings to see the actual DOF when using the smaller sensor (~3/4 stop for apsc and ~2 stops for 4/3).

    Of course framing would also be different but you're only talking about the markings on the lens barrel here which are for the 135 format.

    Gordon
     
  9. Ray Sachs

    Ray Sachs SC Legend

    Sep 21, 2010
    Not too far from Philly
    you should be able to figure it out...
    But there are two problems here. First, the HFD (hyper-focal distance) varies depending on the aperture chosen. So you can't focus on an arbitrary HFD and THEN set the aperture - you have to know the aperture to calculate what the HFD will be. For example at the 28mm setting, the HFD will be over 18 feet wide open at f1.8, a little over 8 feet closed down to f4, and only about 4 feet at f8. So, you need to know your aperture to know the hyperfocal distance to focus at. If you explained that somewhere and I missed it, my apologies, but I don't see it in your post...

    Second, using HFD is a good way to go in good light when its easy to use a smaller aperture in the range of f5.6 (hyperfocal a little under 6 feet so everything from 3 feet to infinity is in focus) and still maintain adequate shutter speeds at realistic ISO's. But in lower light, you can still get a reasonably useful zone of focus that will be a good deal narrower than the huge range that's in focus when HFD is used. As noted above, at f3.5 at 28mm with a focus distance of 6 feet, you're well short of hyper focal distance, so infinity will not be in focus, but everything from about 3.5 to 17 feet should be in focus. This is a very useful "zone" for street shooting but is not close to HFD. Hyper focal is simply the largest ZONE one could use while zone focussing, but many smaller zones are highly useful.

    I wouldn't think about using zone focussing at any focal length longer than about the 50mm equivalent anyway - its not very useful with the telephoto end of the lens because the zone of focus is soooo small. And with a camera like the RX100 where you have to ESTIMATE distance, sticking to an easy focus distance to estimate (such as 5-6 feet for an average sized adult) is a good way to go. And then just work out the "zones" that will be in focus using that particular focus distance at a couple of focal lengths (or just one if that's all you tend to use) for a couple of different apertures, which you'd use depending on how much light there is.

    -Ray
     
  10. porchard

    porchard SC Veteran

    344
    Feb 24, 2013
    Devon, UK
    Agreed - this was my experience when using adapted RF lenses on m43.
     
  11. Ray Sachs

    Ray Sachs SC Legend

    Sep 21, 2010
    Not too far from Philly
    you should be able to figure it out...
    Hmmmm. Maybe the CoC assumption changes with the sensor size based on assumptions about how the "crop factor" will be used??? I don't really know how that's working. But OPTICALLY speaking, it seems to me that a 28mm lens at the same aperture should have the same optical depth of field regardless of whether the resulting light image is going to be left at a wide angle field of view on a full frame sensor, a fairly neutral focal length on an APS sensor, or a fairly long telephoto on a compact camera sensor. I guess the tolerance to that DOF may vary depending on how much you're enlarging a given sensor for printing purposes, but it would seem that the optical properties wouldn't vary... But this is about half a step from getting well beyond my pay grade, so forgive me if I'm missing something...

    -Ray
     
  12. porchard

    porchard SC Veteran

    344
    Feb 24, 2013
    Devon, UK
    You're right - I should have articulated that better in my post...:redface::smile:

    Yes, I absolutely agree - I use HFD only at wide angle settings. It wasn't actually my intention to recommend to the OP that he should use HFD at longer lengths, I simply copied the data which I had derived (some time ago) from the dofmaster.com site... an academic exercise, as it were.:wink:
     
  13. flash

    flash SC Veteran

    372
    May 6, 2011
    Gordon
    Certainly the optical properties of a given lens don't change, regardless of the sensor used, as long as the image circle is large enough to cover it.

    But there's no such thing as "optical depth of field". DOF is an illusion only. Optically a lens has a point (or line or arc) that is in focus and everything else is not in focus. DOF is a matter of perception, not reality. It's the place where we perceive something to be in focus, because we can't register any "fuzziness" even though it's there. So given the same lens, aperture and focus distance the smaller sensor APPEARS to have more DOF because it's subject to a greater degree of enlargement.

    The same thing occurs with different print sizes. If you were to make two prints from an identical file with some out of focus areas in it. Make a 6x4" and a 20x30" print. Viewed from the same distance the larger print would APPEAR to have less DOF. Optically the same. Perceptually different. This can be important because most people (even those who do shoot rangefinder and MF lenses) have no idea what print size the markings on their lens barrels are based on. Then they print to a different size and complain the DOF scale on their lens is wrong.

    Gordon
     
  14. Ray Sachs

    Ray Sachs SC Legend

    Sep 21, 2010
    Not too far from Philly
    you should be able to figure it out...
    OK, makes sense. Thanks for the explanation. Like I said, this was getting beyond my pay grade. I've generally just relied on DOF Master, which I guess takes all of this into account when you crank in the camera body and focal lengths... And I've been well satisfied with the results. But I don't generally print larger than about 12x18", so I can probably get away with more than some folks who print larger...

    -Ray
     
  15. Tom K.

    Tom K. SC Regular

    185
    Aug 17, 2013
    Connecticut.
    Tom
    Folks......I have to tell you. This is the best explanation of zone focusing on the Sony RX100 anywhere on the web. I have looked all over and this thread will be the future reference point for RX100 zone focusing. Man am I glad I found this forum. I thank you all very much.

    Ray.....thanks for looking at my Flickr photostream. The problem I am running into is that too many shots for my liking are focused on the background rather than the subject. I do a ton of hip shooting (which I love BTW). Plus I am using Multi rather than center point as my focusing method. It's just some of the killer shots I could have had missed focus by nailing the background perfectly while my subject was too blurry.

    Street photography is hard......but tremendous fun. I try to use a very fast shutter speed to freeze movement. My best shots thus far have been shot using shutter priority at 1/500th of a second or even 1/640th or 1/800th. But then my aperture ends up being f/2 or even /1.8 at 28mm.

    Anyway......I am grateful to you all for the superb advice.
     
  16. Armanius

    Armanius Bring Jack back!

    Jan 11, 2011
    Houston, Texas
    Jack
    Thanks Porchard, Ray and Gordon. This is DEFINITELY beyond my pay grade. Or brain capacity. I think I better stick with just using the M lenses on the M9. And use the AF lenses on everything else!!
     
  17. aleksanderpolo

    aleksanderpolo SC Regular

    112
    Apr 18, 2013
    Polo
    I think it is the opposite?

    Plugging in the number to the DOF calculator, for example 50mm f1.4 at 10meter.

    The DOF for FF at f1.4 is around the DOF for APSC at f2.1. That means the DOF marking for 1.4 on a FF lens would be applicable to the DOF at f2.1 when the lens is used on APSC.

    This sounds counterintuitive, but that's because most of DOF discussion is comparing two lens with different actual focal length on different sensor (e.g. 18mm on APSC vs 28mm on FF), not the same lens on different sensor.



     
  18. Tom K.

    Tom K. SC Regular

    185
    Aug 17, 2013
    Connecticut.
    Tom
    If I get the hang of this it will make my street shooting life much easier. I want to be able to set the camera per the instructions and simply worry about nothing but getting the shot in focus. Then I can concentrate 100% on shooting and not have to think about wether the subject is in focus or not.

    BTW.....I shoot the RX100 exclusively at 28mm for street photography.

    Many thanks.
     
  19. porchard

    porchard SC Veteran

    344
    Feb 24, 2013
    Devon, UK
    That's even better, then! You have only one formula to remember:thumbup: i.e. 10/Av (or 33/Av if you're working in feet rather than metres:smile:)

    Again, these figures are rounded - we're hardly talking "ultimate precision" here, anyway!:wink:


    BTW, it has just dawned on me that I made a leap from your original enquiry about zone-focus to hyperfocal distance, right from the outset.:redface::rolleyes:

    Apologies for that (my excuse: it was late(-ish) last night when I replied to your first post), and I hope that the HFD stuff was useful... or at least, of interest!
     
  20. Ray Sachs

    Ray Sachs SC Legend

    Sep 21, 2010
    Not too far from Philly
    you should be able to figure it out...
    Tom, no offense to Porchard, but I just don't think those numbers are right. If you shoot at the 28mm equivalent (the actual focal length is 10.4), your hyperfocal distances, according to DOF master, are approximately (I say approximately because they don't have 10.4mm available as a focal length, so I had to use 10.5):

    f1.8--------------------18.5 feet
    f2.8--------------------11.7 feet
    f4------------------------8.3 feet
    f5.6--------------------- 5.9 feet
    f7.1----------------------4.7 feet

    I wouldn't see any reason to shoot beyond f7.1 with this camera, probably wouldn't go past f5.6

    So, at f5.6 in good light, you focus at six feet (easily done for most adults, by focussing from somewhere around the top of your head or a few inches higher or lower - depending on your height - to the ground), and everything from about 3 feet to infinity is in focus. Using the previous numbers, I'm not sure where 10 meters (or about 30ish feet) as a hyperfocal distance comes from - even wide open at f1.8 its well short of that at 18.5 feet. And even if it WAS at 30 feet, you wouldn't want to use that because it would mean that everything from about 15 feet to infinity would be in focus. Most of your shots on Flickr are taken of subjects WAAAAAAY closer than 15 feet. I'd say that some of them were closer than 3 feet, so even using the hyerfocal distance of 5.9 feet at f5.6 might not always get you close enough, although it generally would. If you focussed at 4 feet at f5.6, you'd have everything from about 2.4 - 12.5 feet in focus, which might work better for you on some of your shots. But, for heaven's sake, please don't try to focus at 30 feet!!! First of all, its nearly impossible to estimate, and second of all its just waaaaay too far, even if it was right which I can't see how it is.

    Again, I would put the emphasis on a focus distance you can easily estimate. I think six feet or two meters is a good place to work from. Most adults can estimate this easily by holding the camera at about the level of the top of their head or slightly above, and using auto-focus to focus on the ground. At f5.6, you're pretty much AT hyperfocal distance and you've got from 3 feet to infinity in focus - so just about EVERYTHING except extreme close up is in focus. And in lower light, if you need to go down to f3.5 (which you can use at ISO 3200 and still maintain pretty reasonable shutter speeds - 3200 still looks OK on the RX100, especially in B&W), you'll have a zone of focus from about 3.6-17 feet. This is still a very useful zone for an awful lot of street shooting.

    Zone focus is a hugely useful and effective tool, but you have to have the right numbers or at least very close to the right numbers. If Porchard can show me how his numbers work, I'll be happy to listen, but using DOF Master, I honestly don't see how he came up with them. If you want to do some of this for yourself, you should familiarize yourself with DOF Master - its got a VERY easy online calculator and the RX100 is one of the many cameras in its database that you can choose from. The thing you have to remember is to use the ACTUAL focal length, NOT the equivalent focal length. The actual range of the RX100 is 10.4mm to 37.1mm, NOT 28-100mm. Here's the website to get started, if interested:

    Online Depth of Field Calculator

    -Ray