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"Look deep into nature, and you will understand everything better."


Albert Einstein

Thursday, September 29, 2011

A Question of Sharpness in the Deep Woods

I took a short hike the other day in a state park about 10 miles from my home, mainly just to scout a stream that leads to a small but very pretty waterfall (this shot is the stream, not the waterfall). I brought a camera, one lens (the wrong one, I think) and a tripod. The place was still as mysterious and pretty as I recall and I spent more than an hour shooting, despite the fact that the sun had already gone below the western ridge and so it was like hiking in very deep twilight at times. There were also more mosquitoes than I had anticipated!

Anyway, as anyone who knows me already knows, I'm not a big spender when it comes to camera gear. That's mostly a financial consideration, by the way, I have nothing against owning great cameras and lenses, but I've rarely had the funds to do that. But there is one thing I demand of most of my photos: ultimate sharpness. And that is why I'm so frequently disappointed by my images: I simply don't own the high-end lenses that I need to do the type of work I know I'm capable of--and it's intensely frustrating at times.

Take, for example, the shot above. I did everything I know how to do to make a sharp photo. I used a moderately heavy-duty tripod, used a fairly good (not great) Nikkor lens, was careful to clean the front glass and the filter and used a self-timer to activate the shutter so that I didn't jiggle the camera (using the timer is a good idea, by the way). And yet, the photo is not nearly as sharp as I'd like. I've examined about two dozen frames from that day and I'm simply not sure where the fault lies. I was shooting at ISO 400, which should not be a noise or quality concern. And for most of the shots (not this one) I shot at a very small f/stop (f/22 on most shots) to get good depth of field and, again, I use a tripod for everything. I rarely shoot without a tripod.

There are several possible things that can make a photo unsharp:
  • Using a poor-quality lens
  • Using too small an aperture (even though this provides more depth of field, it may also cause optical issues and most lenses are sharpest at their middle aperture, around f/8 or f/11)
  • The camera was jiggled during exposure, even if you are on a tripod (a camera strap blowing in the breeze may have been the issue here, but I don't think there was a breeze)
  • Using too high an ISO can introduce "noise" that can soften an image
There are other potential issues, too, like where you are focusing (that changes the depth of field pattern). But as I said, I am very methodical and careful, so when I come home and the sharpness isn't there, I'm frustrated and it sends me to the expensive gear catalog wishing I had better lenses (that would help, by the way). I used an 18-70mm Nikkor here, an amateur lens--but one that is normally very sharp.

Anyway, perhaps I'm too critical (I'm not) or I just screwed up in some way. But I hate unsharp images. It has been an issue with me since I was 10 years old. I do sharpen images in Photoshop (using the unsharp masking tool, but in a somewhat complex way that a friend showed me) and it helps. But when I look at my old 4 x 5-inch negs and see what real sharpness is, I know when an image falls short. That brings up another issue: sensor size. Bigger sensors are better.

So, I'll continue to fight this battle. And if I win the lottery or if book publishers ever stop screwing me out of royalties (don't ask), I'll buy better gear.

But I know one thing for sure: my next digital SLR will have a full-frame sensor. The bigger the sensor, the bigger the pixel and the bigger the pixel, the less I'll whine about sharpness. Please feel free to leave comments.

I'm thinking of self-publishing my next book, by the way--if you have any experience in ebooks, let me know how you did.

Photo notes: This shot was shot nearly wide open at f/4.5 and so has very little depth of field, but is, oddly enough, sharper than the images shot at f/22 or f/25. It was exposed for 1/6 second at ISO 400.

4 comments:

Brian Oglesbee said...

I feel your pain. I hate it when despite my best efforts the pictures aren't sharp! I definitely find that with the 85mm tilt/shift Nikkor I use most of the time the sharpness seems to be best between, say, f5.6 and 11. I did some tests and when looking at the files at 100% found the sharpness noticeably declined at the extreme end (f22 to 32). Also, do you think the focal length your zoom lens was set at for the creek shot may have something to do with it? Here's another focus-related question: have you ever noticed that some lenses are really sharp when you're focussed close but not as sharp at infinity?

Frank Kautz said...

Hi Jeff,

Are you using a filter on the lens? I have found that the filter sometimes causes the loss of sharpness.

By the way, thanks for the Vermont tips. It rained most of the weekend, so I didn't get to get much outside, but I did have fun.

Frank

Jeff Wignall said...

@Brian, Yeah, I wonder about what the focal length is, because I shot some close-ups of ferns the same day, same locale, and they are blazingly sharp. (Did you know that on some Nikon bodies you can adjust the focus of the lens via a built-in focus test? Your camera probably has it Brian--then you set that adjustment and the camera automatically knows when you mount that lens and adds in the correction.

@Frank: Yeah, I do use a UV filter over the lens and if focus is critical, I take it off. That day the filter was on, in fact, but I took pains to clean it well. I do have some very high-end filters (B+W brand, about $100/each) that I used on my 105mm Micro Nikkor for close-up work, but I sold the lens this past winter to heat the house. Heat vs. Lens and the lens lost :)

Jeff Wignall said...

Frank, too bad it rained! Bummer!