Tag Archives: Nikon D40

Variable ISO – a useful exposure tool

Thom Hogan posted some interesting ideas on his site yesterday, pertaining to the question of how we, as photographers, deal with setting exposure. Basically, in the film days, we were stuck with one ISO rating for an entire roll of film (and some of us habitually used only one type of film), so at that time, ISO was essentially a fixed value. To adjust exposure, we then had to adjust shutter speed and aperture.

Today, ISO can be varied from frame to frame, and on some cameras, there is quite a wide degree of choices available. Hogan’s idea, then, is that having a selection of finely adjustable aperture settings may not really be necessary. We pick one of our two or three preferred apertures (wide open, optimal sharpness, or maximum depth-of-field prior to diffraction), then vary the shutter speed and ISO (if needed) to get the exposure we want. The point then is that we don’t really need a whole slew of apertures to choose from.

This talk of varying the ISO brought to mind something similar that I’d been considering writing about. I got a longer lens late last year, a 300mm, which on my reduced size sensor equates to a 450mm field of view. That’s long enough to make it a significantly different animal compared to other lenses I’ve used. Furthermore, it does not have vibration reduction. On the other hand, while it’s a somewhat hefty lens, it’s weight is well within reason for hand-held use. The problem then becomes ensuring that the shutter speed doesn’t go down far enough to result in problems. In practice, I discovered that I was most comfortable keeping it around 1/800 of a second or higher. That speed allows me some leeway, meaning I can get away with sloppier shot discipline, basically. If I went down to 1/500, I would have to be very careful to hold it steady as I released the shutter, and the overall percentage of blurred shots would be higher regardless. Another thing I ran into relates to a peculiarity of my camera (a Nikon D40): higher shutter speeds sometimes seem to result in weirdness. This is sort of hard to describe, and I’ve never really been sure what the hell is going on when it happens. I suspect it has something to do with the electronic shutter that this camera uses, in that it can sometimes create some weird artifacting effects at higher shutter speeds. The anti-aliasing filter may also be a factor, or possibly the lossy compression, even though it makes no sense at all that shutter speed would interact with either of those things. I don’t honestly know what it is. However, the practical implication of it was that I realized it would work very well if the shutter speed was at 1/800 all the time, at least for hand-held shooting with this lens. Well, there’s an obvious solution to that, isn’t there? Shoot in shutter-priority mode.

The one question was what would happen when the lens opened all the way up. It’s only an f/4 lens, which is not fast enough for shady conditions or heavy cloud cover at 1/800. So I turned on AutoISO, a feature I hadn’t used on my camera in a couple of years, and which I had never ever tried in shutter priority mode. I actually wasn’t even sure it would do what I needed it to, which was to keep the camera at the base ISO of 200 until the lens was wide open, then raise the ISO upward if there wasn’t enough light. Turns out, this is exactly what it does, and it works very well. I totally recommend it, at least for Nikon bodies with this type of AutoISO, and similar non-VR long lenses. It would work with VR lenses, too, if I had some particular reason for not wanting to use the VR, such as bokeh optimization.

On other camera bodies, such as the D7000 which I will have in the not too distant future, it wouldn’t be necessary to do it this way. The D7000 has more flexible AutoISO settings. On the D40, when using AutoISO in the more typical aperture priority mode, the highest setting allowed for “minimum shutter speed” is 1/250th of a second, which is not fast enough for a lens like this. On a D7000, I am not sure what the “maximum minimum” is, but I know it’s at least 1/1000th of a second. So on a D7000, I could just leave it in aperture priority mode, set up AutoISO to allow a minimum shutter speed of 1/1000th of a second, and viola!, I’d be set to go. That camera also does not have an electronic shutter, so that particular weirdness would presumably be gone, meaning I’d have no reason to avoid very high shutter speeds.

In the mean time, though, I have accumulated quite a collection of 1/800 second shots, many of them at f/4 and weird ISO values like 520 that result from the AutoISO setting. I’ve so far only run into one instance where the camera maxed out at ISO1600. The resulting shots were about one stop underexposed, but actually looked pretty good anyway.

That, of course, leads to the other big consideration with this, which is how high can you push the ISO? There was a time when I would not have been willing to use ISO1600 on a D40. However, more recently, I’ve come to realize that the noise inherent in that setting is really not all that bad. The amount of detail lost is pretty minimal, and the noise reduction in Lightroom 3 does a pretty good job at keeping the noise under control. As long as the photo isn’t extremely underexposed, the result is a somewhat grainy looking picture, sort of like Ektachrome 400, back in the day. (Although, frankly, a D40 RAW image at ISO1600 has better color than Ektachrome 400 ever did.)

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D7000 or D300s?

I’ve been meaning for a while now to upgrade my camera body (a Nikon D40), and had pretty much decided on a Nikon D300s body. Then the D7000 body was announced, and the specs turned out to be so close to the D300s that it raised the question of whether the extra few hundred bucks for the D300s would be worth it. Prices on the D300s seem to have come down just a tad since then (or maybe that’s my imagination), and the D7000 body is still hard to get a hold of if you don’t want the kit lens. I had actually been leaning towards the D7000, since it does have some nice features that seem to improve on the older body, such as higher ISO capability, and better video function. This was in spite of the fact that right now I make do with a camera with a practical limit of ISO1600, and that I know nothing about video at all.

So it was a welcome development today when I encountered this review which is actually somewhat critical of the D7000. There’s a lot there worth reading, including the comments. In particular, this comment, does an excellent job of cutting through all the hype and bullshit surrounding the newer camera, taking it down to just a quick, simple summary of the advantages of each body.

What it boils down to is that the D300s is better built, has a better grip, a better autofocusing system (in fact, its CAM3500DX system, shared with the D700, is considered an industry leader at this point), “more professional buttons” (in particular, the AF-ON button, which I think would be useful for my purposes), and can use compact flash cards. The best points in favor of the D7000 are better metering, and better high-ISO capability. It’s also lighter. On the other hand, there has been some question surrounding the shutter release button on the D7000, with some claiming that it’s too sensitive, and can’t be used with gloves. This is important, due to the fact that I do a fair amount of outdoor shooting in the winter, and have no desire to freeze my fingertip off. :) Some have also criticized the grip, saying it’s too slippery, and smaller than earlier cameras like the D90.

Anyway, it’s some food for thought. I wonder how the D300s replacement (D400?) will stack up? Rumors are that it’s due for release sometime next year. In theory, it should blow the D300s out of the water, but things like ergonomics and button-pressure are precisely the sort of changes which really can’t be predicted. In those respects, the newer camera may not be as good as the old. (In general, technology is like that. “Upgrades” always focus on marketable characteristics, and not on vague, fuzzy concepts like “actual usability.” This is why I gave up being a gearhead. It was too frustrating.)

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Camera geekery of the day!

This is why I read Ken Rockwell:

Nikon D3100, D40 and D3 High ISO Comparison

Who else would even think to do something like that? And it’s a genuinely interesting comparison, too, not just because I am a D40 user, but for a more substantive and technical reason: If you do the math, it turns out that the individual photosites on the D40 and the D3 sensors are pretty close to the same size. That means what you’re seeing in these photos, if you compare strictly the D40 and D3 shots, is a pretty good comparison of how Nikon improved its sensor noise handling technology between those two generations of cameras. It’s really a striking illustration of how dramatic the improvement was, at ISO1600 and beyond.

It’s also a pretty good exemplar of how well the D40 handles itself at ISO 400 or even 800. (The colors do tend to be a little duller on the D40 shots, but I’m guessing that’s because the D3 and D3100 have Nikon’s Picture Control feature, while the D40 doesn’t. That would mean the D40 is using different JPG conversion parameters, so it’s not surprising that the colors look different.) The D40 ISO800 shot looks almost as good as the base ISO200 shot. This matches my own experience: I’ve found that ISO 400 is quite usable when an extra stop is needed for wildlife or what-have-you, and I can even use ISO800 to get acceptable results if I need to. Yes, there is more noise at that sensitivity, but as Rockwell says, it’s not just about the noise. Noise can be dealt with. The level of detail retained in the photo is the key issue, and it appears to be roughly the same at ISO400 and 800, with ISO200 having a bit of an edge. This supports my belief that, in terms of bumping up the ISO sensitivity, the D40 is the best of its generation of cameras (namely the D100, D70, and D50). I would also guess it handles those speeds better than its immediate successors (namely the D40x and D60…not so sure about the D3000, though).

Pro-D40 ranting aside, the other interesting thing about that page is how clearly it demonstrates that the D3100 is a step up from the earlier generation of camera. It’s only at ISO6400 that the D3 begins to look significantly better than the D3100. Compare this to the D40, which is essentially crap at ISO3200–in fact, it doesn’t actually have a proper ISO3200 setting, it’s actually “HI 1”, and it can’t shoot at ISO6400 at all.

Now if only the D7000 was out so it could be included…

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