Multiple Focus Points

Forums All About Photography Multiple Focus Points

This topic contains 39 replies, has 6 voices, and was last updated by Profile photo of  Anonymous 4 years, 6 months ago.

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  • #3599
    Profile photo of Ian McNab
    Ian McNab
    Keymaster

    Ken said, “…Bride in white dress and groom in black suit–spot metering is not the mode.”

    How about spot metering the white dress and adding 2 stops to shift it from Zone 5 to Zone 7?  😉

    #3601
    Profile photo of D. Williams
    D. Williams
    Participant

    Oh for 51 focus points!  😉

    Those sound like fairly nifty cameras Ken. It is interesting to hear what methods we all use for sharp focus where we want it. Very helpful.

    #3603
    Profile photo of
    Anonymous

    Spot metre white dress equals correct exposure. Close down two stops equals white dress under exposed. Increase by twostops /white dress over exposed.

    #3604
    Profile photo of Ian McNab
    Ian McNab
    Keymaster

    Spot meter white dress = white dress exposed as mid-tone grey = unhappy bride.

    Spot meter white dress + increase exposure two stops (-ish) = white dress exposed as white = happy bride! [1]

    (Remember that your light meter is dumb: it assumes light is being reflected by a mid-tone grey surface, and it calculates the correct exposure for that.  Hence it will give you settings that will under-expose light scenes / objects and over-expose dark ones.  You have to correct for this, either with ‘exposure compensation’ in automatic modes or with adjustments to speed / aperture or ISO in manual mode.)

     

    [1] All values a bit approximate, depending on amount of light and reflectance of materials.  (What colour is white, really?)  If in doubt, use an incident light meter, not the reflected light meter in your camera!

    But even the incident meter will give the correct exposure for so-called “mid-tone grey” only.  Ansel Adams had a running battle with manufacturers for years about whether light meters were really working to 18% grey or to 12%, as he determined.  Too arcane by half, eh?!  If you really want to know more read these:

    http://www.bythom.com/graycards.htm

    http://www.richardhess.com/photo/18no.htm

    🙂

     

    #3605
    Profile photo of Peter Robinson
    Peter Robinson
    Keymaster

    I’ve always found exposing for a bride in a white dress and a groom in black a compromise. Especially in with a harsh sun in contrasty situations. The sensors just cant cope with very high contrast, but if you shot in RAW you can recover a lot of detail. If you’ve got a very patient couple who can keep very still you could try bracketing at 2 stops apart, then use HDR to merge them. It’s not very practical at a weeding though. Better to move the couple into the shade.

    If you spot meter on a bright white dress the whole picture will go dark and the dress will be best exposed, but still under exposed from my experience. If you spot meter on the dark suit the picture will be over exposed and the suit will be lighter than it should be. I would meter on a face which is nearest to a mid tone which hopefully give a compromised exposure which I could improve using a RAW converter.

    #3606
    Profile photo of Ian McNab
    Ian McNab
    Keymaster

    Peter said, “If you spot meter on a bright white dress the whole picture will go dark and the dress will be best exposed, but still under exposed from my experience. If you spot meter on the dark suit the picture will be over exposed and the suit will be lighter than it should be.

    Yes, that’s exactly the consequence I was referring to Peter – the meter thinks the dress is grey, so pulls everything down;  or it thinks the suit is grey, so whacks everything up.  You therefore do have to compensate for the dumb meter!

    I would meter on a face which is nearest to a mid tone which hopefully give a compromised exposure which I could improve using a RAW converter.

    Or if you don’t have someone from the Indian sub-continent to provide that tonality, spot-meter a Caucasian face and add about a stop or so!  As you suggest, getting the faces right is probably more important.  But brides don’t like you to mess with their dress – or their bride’s maids’ dresses!  (I had a problem once shooting a party under mixed lighting – tungsten + fluorescent. Yuk! – and to get the facial tonalities right the hostess’s dress, which was Cadbury’s purple, had to finish up looking Royal blue.  Yet another reason for preferring BW photography!  But this is off-topic: colour balance, not exposure.)

     

    #3607
    Profile photo of
    Anonymous

    Never

    #3608
    Profile photo of
    Anonymous

    Sorry Dennis-nothing to do with multiple focussing points.  I took a spot meter reading off the white petals as it is those I wished correctly exposed. This darkens the room surrounding. Had I increased the exposure to bring detail in the room -then the petals would be over exposed.

    #3621
    Profile photo of Ian McNab
    Ian McNab
    Keymaster

    OK.  Below are three photographs, all of the same subject: a piece of white mount board and a piece of black mount board side by side.

    All three pictures were taken in the same diffuse natural light from a window, with a Nikon D300s camera and 50mm f/1.8 prime lens.  All the images were taken at f/4;  shutter speeds were adjusted to get the correct exposure, measured as per the description that precedes each image.

    The camera RAW files were converted to jpg in Lightroom, and a thin black border added in Photoshop.  There was no other adjustment or post-processing.

     

    Picture 1: incident light at the centre of the subject measured with a Sekonic L308s meter

     

     
    Picture 2: spot metered on white side using in-camera meter

     

     
    Picture 2: spot metered on black side using in-camera meter

     

     

    As you see, the Sekonic meters the exposure for incident light as equivalent overall to what a mid-tone gray card would reflect.  The camera spot meter also gives an exposure correct for a mid-tone grey subject, and the settings it provides therefore make the white look mid-tone grey in picture 2 and make the black look mid-tone grey in picture 3.

    To get the white looking white in picture 2, you’d have to increase the exposure;  and to get the black looking black in picture 3, you’d have to decrease it.

    Either way, you’ll only expose one of the tones correctly.  But notice that even the incident metered tonality in picture 1 is a compromise: the white is a bit too dark and the black is a bit too light – the ‘correct’ exposure given by the meter pushes them both towards… mid-tone grey!

    This is why Ansel Adams had to work out a way of adjusting the light tones and the dark tones separately by the way he exposed and then developed the photographs.  And he was also ace at selective dodging and burning during the printing:  hence his three books – “The Camera”, “The Negative” and “The Print”.

    #3622
    Profile photo of
    Anonymous

    Ansel Adams–from a well heeled family   poor sole passed away in 1984 and like so many old pro”s never needed a light meter-his main interest was landscape and would look up at the sky and say 30sec   f8–job done. He also used large format for the higher resolution. Great conservationist  was Ansel–hopeless at golf–beat him every time.  Oh -spot meters–mode used to determine precise exposure for a given subject.

    #3624
    Profile photo of John Royle
    ajroyle
    Keymaster

    Wow, a long thread – well done you guys!

    Like you I normally only use the central focussing spot, then press the shutter release half way to lock the focus and recompose.

    The natural history people tend to be fussier about this because focussing with telephoto lenses is far more critical and they have moving subjects to contend with.

    For many shots HCB would not have had to focus, the lens being preset manually to cover the distance that he expected  his subjects to be. 35mm on a 35mm camera gives you lots of flexibility because there is a decent depth of field.

    On the Leica M you have only two choices for exposure; M3, M2, M4 had no exposure meter the M5 and M6 had a built in one, the M6 just has a light sensor facing backwards to a small white spot on the shutter blind – so I suppose you would call it “centre weighted”. You just choose your shutter speed OR aperture and then move the aperture ring or shutter speed dial until two red lights in the viewfinder are both lit.

    Now it is all too complex!!

    I used to just angle the camera down a bit for landscapes and open up a stop to a stop and a half for snow scenes!

    #3625
    Profile photo of Ian McNab
    Ian McNab
    Keymaster

    Ken said, “…Oh -spot meters–mode used to determine precise exposure for a given subject.”

    Yes, Ken – as long as the subject has the same overall reflectance as mid-tone grey! 😉

    (PS Ansel did use light meters:  Westons with black-painted cardboard tubes to reduce the angle of view early on;  a Pentax Digital spot meter in his later working years)

    #3632
    Profile photo of Ian McNab
    Ian McNab
    Keymaster

    OK, back to multiple focus points. When does it make sense to use them? When the camera is mounted on a tripod, and “focus & recompose” is therefore frankly impracticable.  You frame the shot, leave the camera stationary, track through the focus points to the right place, focus there, and Bingo! (Having 51 focus points to choose from on a Nikon is genuinely helpful in these circumstances.)

    But for hand-held photography, it’s simpler and quicker to use the central focus point to “focus & recompose”, as it involves fewer button presses.

    Don’t you think?

    #3634
    Profile photo of Dennis Crabtree
    Dennis Crabtree
    Participant

    Agreed.
    My thoughts were that with multiple focus points at least one of the points would nearly always find some area of focus for the beginner to produce an acceptable image.

    #3635
    Profile photo of Ian McNab
    Ian McNab
    Keymaster

    Dennis said, “My thoughts were that with multiple focus points at least one of the points would nearly always find some area of focus for the beginner to produce an acceptable image.

    That might work OK with a small aperture, and therefore very big depth of field.  But if the aperture were wide (f/2.8, say) and the camera chose a focus point that was different from what you wanted as your subject, Auntie Mary (the intended subject) would be out of focus and the large cow standing 10 feet behind her would be in focus! 😉

    Locking the central focus point and using that to focus, then recompose is probably a safer bet for the beginner.  The recomposing while holding the shutter release half-way down to lock the focus perhaps needs a bit of practice;  but I think the reliably better results will in the end be less frustrating than blindly hoping the camera will guess right what you’re trying to do. 🙂

     

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