As most of you already know, Volkswagen was recently caught cheating on emission tests. But were they really alone in doing so? The EPA data shows some suspicious patterns.
Without getting too technical (in any case, the specifics are still unclear), there's a tradeoff between fuel efficiency, and NOx emissions. So for a given level of performance, the software that controls a modern diesel engine can be tuned so that it is more fuel efficient, but produces more NOx, or it can be tuned so that it is less fuel efficient, but produces less NOx.
Since Volkswagen had problems meeting the NOx standards in the US, they decided to introduce software that detected when an emission test was being performed, and tuned the engine so as to decrease NOx production, in the process potentially worsening fuel economy relative to regular driving conditions.
One possible outcome of this procedure is that the cars involved might actually have better fuel economy in real life conditions, than during …
I just upgraded from a D90 to a D750, and I decided to buy a superzoom to use when I don't want to carry around the full bag of primes. It was a tossup between the 24-120 and the 28-300, but in the end I picked the latter since I already had a 24mm f/2.8D which had been collecting dust during my decade of using DX-sized sensors. In fact I might trade the 24mm with a 20mm if the opportunity comes along.
Anyway, there's a lot of controversy surrounding this lens, so I thought I would make some tests to decide whether to keep the lens or not, and since I have them, I figured I'd post them online.
So here they are. The first one are 200x200pixel crops (roughly) from the center of a resolution target. I took every marked focal length, and every full stop of aperture. I put a green dot next to the combinations that I considered satisfactory. For comparison, the "Optimal" square was obtained by taking a photo much larger version of the same pattern and scaling it down …
Here's a fun technique. I think it's new, but if somebody else has already done this or something similar, please feel free to correct me. The technique allows you to
simulate very directional lighting even on days with so-so lighting, but
it does take a little bit of planning.
Let's say you're out and about shooting photos, and there's a light overcast/mixed cloudy sky. If you wait until a break in the clouds hits your subject, you can take photos like this one:
Decent, but nothing too spectacular. How could you make the lighting more dramatic? One option would be to mess around with levels or curves, but that's going lead to clipping of highlights and/or shadows, pretty soon. Like so:
So here's my idea. First you wait until the clouds move a bit and your subject is in shade. Then you take a SUPER boring picture like this one from exactly the same camera position. This photo has completely diffuse lighting and next to know threedimentionality: