Fresh Dew on a Rose

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I took a photo where I changed the aperture of the lens during the exposure. I was hoping to get a cool or unusual effect, but I didn't. Why not, and is there any really interesting effect that I can get by changing the aperture mid-exposure?

I know that changing settings within an exposure can yield interesting (artistic) results. For example, changing the framing lets you blur the background while retaining a sharp image of a fast-moving subject; zooming in or out surrounds the in-focus subject with a neat effect; you can do several things by changing the lighting, from light painting and light trails to long exposures and using flash with first- or second-curtain sync.

I was wondering what else I could change, and since I don't know how to change ISO or what it means to change shutter speed mid-exposure, I wanted to try changing the aperture during the exposure by rotating the aperture ring on a lens during a very-long (long enough for me to change settings with some accuracy) exposure.

I took a photograph in a dark room that was exposed correctly at f/2.8 and 4 seconds. I decided to use 4 aperture settings, each accounting for 1/4th of the overall exposure. Since my lens has an aperture range from f/2.8 to f/22 (in half stops, so I had to click through two "settings" for each stop), I decided to use f/2.8, f/5.6, f/11, and f/22. That gave me this table of the amount of time to spend at each aperture:

  • 1" @ f/2.8
  • 4" @f/5.6
  • 16" @ f/11
  • 64" @ f/22

which I think should result in the same exposure (Ev=Tv+Av) as 4 seconds at f/2.8.

I hypothesize that this combined exposure will give me a final image very similar (both exposure and depth of field) to a a 32-second exposure at f/8, although I'm hoping something unique or cool will happen.

I focus on some foreground objects on a table, set up a timer so I can count seconds, start holding down the button on the remote shutter release, wait one second, rotate the aperture ring 4 clicks as quickly as possible, wait another four seconds, rotate through 4 more clicks, and then another 4 more clicks sixteen seconds later, and then wait sixty-four seconds and then release the button on the remote shutter release. I look at the result, and... I get a pretty normal-looking picture.

enter image description here

I set up my camera for a 32-second exposure (by setting the shutter speed to 30 seconds), set the lens to f/8, and take the picture, and get a somewhat-similar picture.

enter image description here

I look closer at the two pictures, ping-ponging between them in my image viewer trying to spot differences, and I see:

  • the variable-aperture exposure seems to have a very slight bit of camera blur, which I assume is from me moving the camera slightly during the exposure while rotating the aperture ring.
  • the variable-aperture exposure has slightly less contrast. Perhaps that's just an artifact of the camera blur? Or maybe it's because the exposure setting isn't exactly the same as the constant-aperture exposure, since it takes a little bit of time for me to change the aperture, and the lens spends some small amount of time at several intermediate apertures, and because I've introduced some human error in the timing by not changing settings at the exact seconds specified in my table.
  • the foreground objects (glass of water and camera) appear to be pretty much identical between the two exposures, with the exception of some of the reflections in the water glass, which I assume are due to me and a cat moving around during the exposure.
  • the background books are much more in-focus for the variable-aperture photo. Did I just reinvent focus stacking, or is there something else going on here? enter image description here

So, back to my original question: is there anything I can do with this technique to get some interesting or unique effect? Can I compose the scene differently or change the focus point to get better results? Would a different selection of apertures yield a more interesting effect?

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7 Answers 7

up vote 6 down vote accepted

The only idea I have for something mildly interesting is to create a photo with sharp subject that has out of focus "halo" around it.

  • use a light color subject and a dark background

  • set aperture to wide open

  • focus so the subject is completely blurred (the more out of focus the better)

  • start the exposure, mid exposure stop down all the way to make the subject sharp

  • experiment with different time ratios between wide open and stopped down until you like the effect

  • you can try to add some low power flash while stopped down to make the sharp version even sharper, just make sure the light does not hit the background

I didn't test this because I don't have a lens with an aperture ring but I tried to do something similar by changing the focus - not the most impressive picture I've ever shot but at least it gave a unique special effect.

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ooh ooh ooh! This sounds exciting! I will give it a shot, thanks. –  drewbenn Mar 26 '12 at 18:24
@drewbenn did it work? Using Orton effect you'd achieve the halo described here with a sharper image of the subject. –  Imre Mar 30 '12 at 20:21
@Imre yes I got some good results, along the lines of what I was originally hoping for; the best came from splitting the exposure between two apertures. I want to get some better shots (need to work on composition: get the subjects farther from the background) then I'll post some of them in an answer. –  drewbenn Mar 31 '12 at 4:34

For a static scene, I'd expect the results to have DOF almost as deep as at the tightest aperture (you do record details at that aperture, but they are somewhat blurred by wider apertures - reducing contrast), with some camera shake mixed in. Indeed, this would give an effect very similar to just using an in-between aperture - not very exciting per se.

To have the method resulting in something more unique, something should change in your scene while you're changing the aperture. For example, you could fire key light with one aperture and fill light with other, making areas lit by different lights have different depth of field. In following example, note how the subject is fully sharp (the rear part would be blurred on a wide aperture shot), while the background is blurred (it would be much sharper on a narrow-aperture shot):

variable-aperture combined with lighting

Single exposure, 58mm f/2 lens; focus on lettering of the other 58mm lens. Exposure started with f/11, key light LumoPro LP120 at 1/2 power snooted almost top-down; aperture changed to f/2, fill light LumoPro LP120 at 1/16 power diffused at left of scene.

For comparison, here's the same image taken with only wide aperture...

wide aperture

Single exposure at f/2. Key light at 1/32 power; fill light at 1/16 power.

...and only with narrow aperture:

narrow aperture

Single exposure at f/11. Key light at 1/2 power; fill light at 1/1 power.

To reduce camera shake and allow for unexposed scene adjustment, you could shoot the different apertures as separate frames and combine them in post. Combined with repositioning an object, this could result in image where the object is apparently blurrier closer to focus plane and sharper further away.

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Thank you so much for taking those pictures! I didn't get what you were saying until I saw the pictures: using flash with variable aperture lets you achieve a different depth of field. –  drewbenn Mar 31 '12 at 5:41
+1 from me. For some reason I immediately recognized the lens but kept wondering "never saw a Zenit camera like that". It took me all the 3 pics to finally notice that it's a Pentax :-) –  Francesco Mar 31 '12 at 11:01
I would think that when changing anything during an exposure, capturing multiple images and fusing them in post would be better than using a single long exposure, except in the situation where something is uncontrollably changing during the shot (e.g. there is something moving slowly through the field of view and one wants it to leave a continuous trail). Having separate images will allow effects equivalent to the changing lighting to be achieved in post, but with much more "interactive" control. –  supercat Jan 16 at 22:59
Absolutely, although it wouldn't be the technique this question was asking about. And intended usage might limit how much you can post-process (e.g. competition rules might forbid fusing multiple exposures). –  Imre Jan 17 at 9:05

I would say you have achieved exactly what I would expect to see with variable aperture photography. The out-of-focus areas in your variable aperture photo seem to have a 'haze' to them (the lack of contrast you refer to), consistent with the wide-aperture, shallow depth-of-field component overlaying the narrower aperture component.

Perhaps choosing a background with greater contrast or with some moving elements would produce more dramatic results but I can't really see what else you could expect from this technique.

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What camera and lens are you using?

If it's a modern camera with an electronically controlled aperture, I would be surprised if the aperture actually changed during exposure. Did you verify the aperture blades closed down each time?

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Ahh, good question. I used an old manual-focus lens with an adapter to mount on my camera, neither of which has electrical contacts to communicate with my camera. I stopped down the aperture in the lens by using the aperture ring on the lens itself. I've used the lens enough times to be confident that the aperture actually changed during the experiment, though to be honest I didn't actually look at the aperture blades or through the viewfinder while taking the picture I posted. –  drewbenn Mar 25 '12 at 17:51

What you reinvented was the soft-focus lens, with the minor quibble that the in-focus subject itself is sharply focused rather than having a diffused glow. The out-of-focus elements, on the other hand, are both partially in focus (due to the greater depth of field of the smallest aperture you used) and partially blurred (due to the narrower DoF of the widest aperture), an effect you would tend to get with a lens that had a lot of spherical aberration using your smallest aperture.

It may be an effect you want to play with a bit more -- in the right circumstances, it could make a great vintage-meets-modern look for, say, product photography. That is to say, with the right levels of contrast and so forth, the look could have considerable commercial appeal in the right markets (think upscale lifestyle products, like fine watches, pens and horrendously expensive booze). Having things in the background and extreme foreground that are understated but identifiable can do a lot for product association, giving the viewer the idea that what you're selling (the sharply focused subject) goes with the rest of the package. The technique would probably work better with more contrast in the out-of-focus areas, particularly with a low key background having feature highlights.

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If you want changes during exposure to cause visible effects you need to select changes that cause drastic visible changes in the photo.

Moving the camera, zooming, photographing moving subjects (light trails) and changing the lighting (including flash and light painting) are all examples where if you took lots of normal photos instead of a long exposure one all the photos would have been drastically different.

If the only change caused by modifying the aperture is depth of field don't be surprised the only change you see is in the result photo is the amount of background blur.

You can try to photograph scenes that include light sources (since the aperture changes how light sources look) or maybe out of focus light sources with a shaped bokeh filter - but I wouldn't expect much (the difference between closed and open aperture are still too minor in my opinion)

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In regards to your last sentence: are you implying that I would get better results if I either used a lens that opens wider (and took the picture at, say, f/1.4, f/2.8, f/5.6, and f/11) or moved my subject farther from the background? –  drewbenn Mar 26 '12 at 6:55
@drewbenn - no, what I wanted to say is that different depth of field is not drastic enough change to create an interesting result –  Nir Mar 26 '12 at 11:49
@drewbenn - I suddenly had an idea for something you can try, posted it as a different answer –  Nir Mar 26 '12 at 12:23

Perhaps adding a burst of flash while at the narrow aperture, and then open up the aperture while dragging the shutter could create something interesting. Or the other way around.

But I doubt it.

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