I set out to demonstrate this yesterday evening in a walk around my neighborhood. I was planning to shoot a row of cars. In fact I did shoot a row of cars. But I also found something unusual that demonstrates the effect better than the car photos, bands of neon tubing wrapped around a column, which I shot with my body against the column, camera point up.
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| 55mm, 5.6, 1/4000 Small f-stop (large aperture): Only the second row of tubing is in focus. |
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| 55mm, F13, 1/1250Medium f-stop: Second, third, and forth row of tubing or bolts in focus. |
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| 55mm, 36, 1/60 Large f-stop (small aperture): Tubing or bolts in focus up to the 7th or 8th row. |
If you look sequentially at the top of each photo, you can see a clear difference in the degree of focus. Even with the camera's smallest aperture the farthest rows of tubing are not sharp.
Implications: Shoot small aperture when you want distant objects to be in focus, such as when shooting landscapes. Shoot at larger apertures to isolate an object from the background.
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I've heard from my tutor, Dave Wyatt, regarding the introductory exercises of the course. It seems he intended to post here but had some problems with logging in, so I'll post now on his behalf. Thanks, Dave.
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The rest of your posts look very well done, I was going to add a comment to the aperture exercise but messed up logging in so have copied it below to save from losing it. It is really just to highlight the importance of not just dialling the aperture down to f22 every time you want more than an inch in focus.
An element of this not touched on yet but important as you progress is choosing the optimum aperture for your photograph. Whilst you may want everything in focus just sticking the lens on f22 isn't always going to be the optimum solution as the smaller the aperture, the larger the effect of diffraction on the image (leading to softer than optimum results). Working methods vary depending on the lens you use but the way I shoot is to use hyperfocal focusing, which basically means I focus on the closest thing I want in focus and check the distance on the lens, then do the same on the furthest, then move the focus dial to half way in between the two and choose and aperture that will get them both sharp. On manual lenses you often get a scale telling you what aperture to use otherwise you have to do it via stopping the lens down and seeing for yourself. This will normally show you the largest aperture you can use to get a sharp result but in reality this usually means a barely acceptable result so generally make the aperture about one stop smaller and you'll be good to go. Generally most lenses have their sweet spot somewhere between f5.6 and f11 so that's the area to aim for, although it will always be better visually to go to f22 that just having half the frame soft if you are after front to back sharpness.
As to why the smaller aperture leads to more in focus, in short it is to do with the 'Circle of Confusion' which i admit sounds like something out of a crap game show. Rather than pointing you towards the nearest Physics text book I'll just send you here as it seems a decent enough explanation and the diagram looks the same as the one I had to learn on a Photography foundation years ago... http://www.cambridgeincolour.com/tutorials/depth-of-field.htm
Interesting reading this comment/feedback from the tutor. I'm no expert but 'll add my comments for interest - so this is what I do if you want to be confused more :D I will however try that tip your tutor mentioned taking 2 focus points. I should test them all !
ReplyDeleteDo understand / find out the minimum distance you can get a focus from the end of the lens. This distance does vary depending on what lens you use. It may also be important if you want some element of the near foreground in focus in addition to the rest of the image.
Of course using all these tips may still not help if you aren't using a tripod and remote shutter release.
My favourite lenses on my full frame camara are my Nikon 50mm f/1.8 (cheap lens at less than £100 new but amazing sharpness) and my secondhand Nikon 20mm f2.8 lens (extremely light, sharp and seems to hardly ever suffer with flare and shows great cloud structure in landscapes)
Some lenses have the infinity sign on the focus ring so manually focusing this can help. In addition Ive also read focussing 1/3 into the image may help (e.g. shutter half down with focus one third into image, then recompose). I find an aperture to around f/11 or just over the maximum I use for front to back landscapes but what do I know, I'm a photography noob!
Anyway good luck on the TAOP course, I think I'm a few excercises behind you and also in the FLIKR TAOP Noobies group (Fratton Freak)
Cheers,
Warren