1. Marc1548

    Marc1548

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    Beginner & new to the forum,. I had an idea of shooting a long exposure night landscape of some interesting trees, with some foreground interest pond,river, etc. & Possibly lightening the tree just enough with a torch. Not an original idea I know but thought it would be fun to experiment, & learn.
    My question is how do you focus at night? Will there be enough light from the torch shone at the tree to focus?
    Also how would you calculate exposure time assuming not enough light for the camera to work it out.
    Is it just trial & error?
    Any tips on this type of photography would be great.
    Thanks.
     
  2. Harlequin565

    Harlequin565

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    Trial & error mostly.

    Making some assumptions...

    (On a crop camera) Wide angle lens, say 18mm (the widest on a kit lens). Set your aperture to f11. Shine your torch on something about 5 feet away. Hold it steady while you focus on it. When you get the confirmation green light, turn the lens off auto focus onto manual (usually a switch on the side). This will stop the camera hunting when you remove the torch. At f11 with an 18mm lens on a crop camera, if you focus at 5ft, everything from 3ft to infinity will be sharp. (Google "Dofmaster online calculator" if you want to know more)

    Set your ISO to 100 and your exposure to 30 seconds.

    Click.

    Paint tree.

    Review.

    If your tree is too dark, you need a more powerful torch, or more time painting (or both). If your tree is too bright, you need to paint for less time, or turn the torch brightness down (or both). If you have background light bleeding through, you need to lower the overall exposure time (from 30s to e.g. 20s).

    That should get you going :) Oh, and welcome to TP!
     
    Last edited: Oct 23, 2018
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  3. ihasa

    ihasa

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    You can visit the scene in daylight and find your focus, and make a mark on your lens barrel, that you can easily line up in the dark later. Failing that, find infinity focus and mark that. Focused at infinity at f11 on a wide angle lens, you'll have a sharp background, and a sharp subject as long as it's at least a couple of yards away. Or at a push, if there are bright stars you can probably use live view to manually focus on them.
     
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  4. Teflon-Mike

    Teflon-Mike

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    If I manage to get not 'a' single tree, but plural 'trees' in the frame, I am guessing I am NOT gonna be all that close to them!

    In olden days, cameras had to be focused manually, by eye or by scale... I still have a few, and the non-SLR's DO need you to work-out or guesstimate the focus distance to set on the scale, either with a range-finder or a tape measure or "Err, how many Estate cars could I park between ma and that tree?"

    NOW, on a Medium-Format film camera, the 'sensor' size is around 6cm by 6cm.. the 'normal' angle lens length on that is about 75mm enter the crop factor.... you shrink the sensor to that of a 35mm film camera, 24mm x 36mm.... the normal angle lens is about 50mm.... shrink that sensor some more for an APS-C sized sensor, about 16x24mm, the normal angle lens is about 35mm..... B-U-T a 50mm lens is a 50mm lens, and it dont know and dont care what size of sensor is behind it.... it has a closest focus distance and a range of critical focus from there to infinity, regardless... A-N-D on shorter focal length lenses, both the close-focus limit and the range of critical focus before infinity, both tend to be closer to the camera....

    So IF you are using a very small sensor camera, like a smart-phone or action cam, this is probably a non-issue.... my little action-cam has a sensor so small, that it has a mere 4.5mm lens, which is a fish-eye on my APS-C Digi-SLR... and with a focal length that short, the close focus distance and the range of critical focus is so small and so close to the camera, its effectively 'focus free'....

    Same phenomena, is used on 'zone-focus' film campact cameras; where with a lens of just 35mm to give a not # 'so' wide angle of view, the near focus and range of critical focus is still so short that with a moderate, say f3.5 aperture, focus doesn't have to be very critical, and you can get away with perhaps just three overlapping settings, near, middle and far.......

    If I picked up my Olympus XA2 zone-focus film compact..... it has three icons for each 'zone'; close focus denoted by a single person's head-and shoulders, middle distance, by two toilet door people, full length, and far distance by a mountain icon..... near focus is nominally 3-6 feet, middle 4feet to infinity, far, 20 feet to infinity.... fastest aperture is f3.5, and this is a 'full-frame' film-camera....

    This suggests, to get more than just one tree in the frame, unless they are bonzia's! You are going to be using a more moderate wide-angle lens, and at something probably tending towards a 'far' focus distance, and even on a full-frame digital camera, you SHOULD be able to pretty much set the lens to 'manual focus', set the hyper-focal focus distance, and NOT have to worry about focusing the dang thing what-so-ever.....

    Of course, what the hyper-foal distance will be, will depend on your exact camera and lens combo, as well as the aperture you select; BUT, it wont be far off the far end of the focus travel on the lens, even if the lens has no scale to go by.

    For the suggested situation, this is probably how I would go about it, and just turn 'off' the AF, and set focus to something close to the end of the focus ring's travel. Or I might start checking the web for clues, depending on whether my intended lens had any sort of user focus scale... but I'd probably also be using an old manual focus lens... if not the camera it was native to, and I WOULD litterally just set it to 'hyper-focus', where even looking through the thing in the dark to compose the shot probably isn't all that accurate or critical!

    Your call... how much of the technology in your hand do you want to be dependent on?

    Focus at around 20 feet, keep aperture over say f-4 and you should be good to go, on almost any Digi-SLR, with any lens or zoom-setting, shorter than about 50mm.
     
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  5. swanseamale47

    swanseamale47

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    Some people use a bright torch to light the subject (my fav), one chap I know uses a laser pen to put a hotspot on his subject (not people) for the focus. Remember to turn off auto focus once you get it, or when you go to take the next pic it'll try to refocus (unless you use back button focus) and you'll have to start again.
    I'd also suggest you set manual white balance, especially if your using torches to partially light your subject, some cameras seem to have a problem with auto colour in low light and can vary from shot to shot.
    Keep in mind trees move in any wind so a still night helps.
     
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  6. Marc1548

    Marc1548

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    Great stuff I did have a look at dofmaster & now have an understanding of sorts of hyper focal distance, on one of my lenses I have a dof scale so armed with the web calculator & that I recon I won’t be far off & to confirm looking at the calculator using the above suggested f stop & lens focal length with the camera I have (Nikon d90; crop sensor) focusing at 5 feet is pretty spot on aswell
    So will put all into practice & hope for the best.
    Thanks for all your help.
     
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  7. scott199

    scott199

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    silly question, but does upping the iso massively in live view, brighten the subject?

    In theory, cant you, up the iso, achieve focus, lock, back iso down and happy days ??
     
  8. Harlequin565

    Harlequin565

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    Good luck!
     
  9. StewartR

    StewartR Efrem Zimbalist Jr Advertiser

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    Arrive on location whilst it's still daylight.
    Focus camera.
    Wait until dark.
     
  10. Marc1548

    Marc1548

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    As an experiment I tried this in my not well lit living room with my Nikon. Firstly I could not alter the iso in live view only out of live view & didn’t seem to make any difference to focusing at low or high iso. Live view as far as I’m aware, is what it is, live view & upping the iso made no difference to brightness in the screen, only changed the exposure settings.
    Maybe other cameras are more sophisticated? But didn’t seem to work for me.
    Worth a question though as Iv learnt something else cheers.
     
  11. scott199

    scott199

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    Thank you, sir, I've learnt something as well. Think I'll try with my D500 as well, i never do night stuff, so never even thought of this, but we are all here to learn
     
  12. Sam Tip

    Sam Tip

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    For focussing, live view with the screen at its brightest is probably the best solution with astronomy-type photography, so it may work well in your context, Marc. As well as the torch, try popping a flashgun around the place for interesting results making sure you're well behind the burst each time. Good luck!
     
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  13. Marc1548

    Marc1548

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    I was thinking just this only today. Iv just got hold of some coloured gels for my flash, might be interesting to throw a bit of colour in there?
     

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