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Thinking of soon attempting snowflake photography again, I pulled out my home-made extension tube. A pseudoscorpion presented itself as a target, so I took a few shots. I’m puzzled, though. This photo is only very slightly cropped, yet it appears grainy or blurry, I’m not sure which. It wasn’t overly dark, so I didn’t have to pull out the shadows a lot. So why am I not getting the sharpness I know my lens can do?
Nikon D3100
Lens 18-55
~4 in extension tube
f/NA
1/200 sec
~35mm with extension tube
ISO 200Attachments:
What happens to the aperture when you remove the lens, and stick your extension tube on the end of it? Does it close down all the way, or open up all the way?
Naturally it closes down all the way, but I have a stick holding the little lever in place. So it is maybe 1/4 – 1/3 of the way open.
Ok, that makes sense. The reason that I wondered, is that the photo looks to me like it went over the “diffraction limit” of the camera/lens setup. Basically, if you stop down your aperture too far, it actually decreases the sharpness, rather than increasing it. If you’re interested in the technical details about, Cambridge In Color has an article that goes into great detail: http://www.cambridgeincolour.com/tutorials/diffraction-photography.htm
The only other thing that I can think of, is that it just isn’t quite focused correctly. I know from personal experience how hard it is to get something perfectly in focus when you’re working with 1:1 magnification or higher. Because you’re stopping down, the aperture is extending the DOF (Depth-of-Field) to partially bring your photo into focus, so it gives an illusion of being somewhat in focus, when it really isn’t. I never saw it so well illustrated as when I was helping James with the soap product photography. When you manually focus, then use the DOF preview button to check your focus, it helps you to understand the significance that aperture plays in how “sharp” a picture is.
I would recommend that you experiment with your lens mounted the “right way” on the camera. Get a small object, and set it as close to your lens as you can, at the lens’s MFD (Minimum focusing Distance). Then use Live View, and manually focus on it, and use your DOF preview button to see what happens when you stop down to f/8 or f/11. Ideally, you’d want a “fast” lens, like an f/2.8, or even a f/1.8 lens, as that will make it a lot easier to visualize.
Hmm… that is a very interesting article. So in other words, I might simply need to open the aperture a bit more. But then I’ll have an even narrower DOF than I did then so the entire bug can’t possibly be in focus. I suppose that might actually be interesting, though, if I were to get even lower and look it in the “face.” 🙂
I guess I should have been using a tripod, too. But since it kept moving every so often, that might have been difficult. My camera doesn’t have a DOF preview button, but I think Daddy’s does. I’ll have to try it out on his.
Thanks for the thoughts! I just need to find another pseudoscorpion…
So in other words, I might simply need to open the aperture a bit more
Well, yes… I guess the only way to really test that theory is to practice. Get a small non-moving object, set your camera on a tripod so it can’t move between shots, and try different aperture combinations. Try to get a good focus, then change your aperture and blow it up to 100% in Lightroom to compare. (Select the photos you want to compare in Lightroom, then hit the “C” key to compare…)
So why am I not getting the sharpness I know my lens can do?
BTW, when you don’t mount a lens on the camera mount, but instead stick black PVC pipe between it, you can’t expect 100% of your sharpness to remain. It’s entirely possible that your PVC lets in some light, which would be called a “light leak”, which would affect contrast/clarity.
Another thing, if your lens is not perfectly aligned with the sensor, it may not focus perfectly either; there’s a reason that camera manufacturers take a lot of pains to make the camera/lens mounts fit perfectly.
If I were you, I would definitely try the 60mm lens for extension tube/macro use. Prime lenses are inherently sharper, so when you’re going to be losing sharpness anyway, you want to start out as sharp as possible.
As I mentioned earlier, you can get a cheapo extension tube for less than $10. This one for example: http://www.ebay.com/itm/Macro-Extension-Tube-Ring-Adapter-for-Canon-Nikon-Sony-Olympus-M42-Mount-Camera-/121177205504?var=&hash=item1c36b96b00:m:m9A1O3-HnrHjOKqirt6XF0g#shpCntId
If nothing else, it makes your setup a whole lot more sturdy, your lens can’t fall off of the extension tubes… 🙂
Thanks for all the suggestions. I tried again… with a wooly aphid this time! 🙂 I forgot to make use of my dad’s 60′, notwithstanding, the photos did turn out sharper – I think because I used a wider aperture and the bug wasn’t moving. I didn’t use a tripod, but I did rest the camera on the table to steady it.
Too true, homemade extension tubes aren’t as trustworthy. I never trust the joints and have to keep two hands on the camera at all times… Perhaps someday, but for the moment I’ve enjoyed getting creative. Next I want to make an external flash from my onboard one… 🙂
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I learned a lot reading through this topic. And I distinctly remember discovering that “illusion of focus” with @buddingphotographer, and how much DOF Preview helped focus on what we really wanted to be focused on!
While probably all the factors that @buddingphotographer mentioned are in play here, it appears to me that the plane of focus is simply too shallow for getting the entire creature in focus, and that it is back-focused. The “floor” and left pincer seem to be sharp enough to indicate this.
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