Saturday, May 12, 2012

HS25 Review – Part 8 – The great LvsM Debate

I hear this all the time.

  • Should I shoot in L size or M size?
  • Fujis should be shot at 16mp because they advertise 16mp.
  • L size has more details at base ISO

The answer to the first question is unequivocal: shoot in M size!

The other two assertions are bullshit.

The typical person prints the odd 4x6 at the local WalMart, Walgreens or Costco. Perhaps an 8x10 here or there. The mavericks print 11x14 at Costco because it is a nice size and it is cheap. But these sizes are well with the 8mp half resolution of the HS25.

If you need convincing of that, go look at Thom Hogan’s excellent article, How big can you print?

So … what this means is that you can put worries of wasting resolution out of your mind. There is no value (short of cropping perhaps) to shooting at high resolution.

But people will still suggest that it is better to shoot L size and downsize. Well, I prefer to upsize, because we are still comparing apples to apples and now we have removed the cropping advantage.

But what about matching exposures? Well, when shooting in the woods with dappled sunlight, the one exposure element that matters most is DR. I set DR400 and let the camera deal with the ISO. Unfortunately, if you want to shoot L size, you will have to shoot at 400 ISO to get DR400.

The example I show below has exposures that look absolutely identical in previews in Bridge. DR400 works perfectly for both to keep blue in the skies and to avoid blowing out sunlit areas. But the exposures are not quite identical. The L sized image is 400 ISO and the M sized image is 160 ISO. Tough cookies. DR100 is not an option, although DR200 might have worked.

Just how many settings do you want to screw with on every shot anyway?

I don’t what to change anything as I walk in the forest. And I don’t. P mode, M size, DR400, Auto ISO 1600 or 3200. And that’s that.

It is a trivial matter to forget to lower DR to get ISO to drop in L mode. And what difference does it make? That’s right. None.

So … the crops at 100%. I upsized the M sized image of a distant section of forest floor, trees and foliage to see how much detail I lose. And, as has happened every time I shot them head to head, the M sized image smokes the L sized image.

The L sized image looks like it was shot through a screen. It has no edge integrity, the textures are flattened, the dimensionality is all gone. In fact, the M size upsized looks like a photograph, while the L size looks like a painting.

This is all blindingly obvious to me.

But some will still say “400 ISO is unfair!”

No, it’s not. First, you need high dynamic range under these conditions. Second, the people who advocate L sized images regularly suggest that 400 ISO is just fine.

Well, I disagree. L size in general opens up the image to a lot of smoothing by the noise reduction algorithms. And it forces you to choose between ISO and dynamic range.

The crops above prove that the point is moot. Shoot M size and stop wasting time worrying about it.