On Sharpness, ISO and Shutter Speed

Started Nov 29, 2013 | Discussions thread
Anders W Forum Pro • Posts: 21,468
Re: On Sharpness, ISO and Shutter Speed

Jack Hogan wrote:

Anders W wrote:

Jack Hogan wrote:

So I have two initial questions, assuming that the data is valid:

1) What are the practical implications for a photographer of the large spatial resolution differences in the V+H directions seen in the newer sensors measured here ? Will it make a difference whether we look at the final image in portrait vs landscape orientation?

Why would it make a difference if we look at it this way or that way? Blur is blur and to my knowledge, the human visual system isn't differently sensitive to blur in one dimension than in the other. Besides, we wouldn't normally want to look at something shot in landscape orientation in portrait mode or vice versa, for pretty obvious reasons.

Yes, I saw that did not come out right but only after having used up my two corrections already. Let me rephrase the question:

If in the A7 and D610 there is really such a large difference in horizontal vs vertical captured resolution, is that an issue in practice? Or should we be preferring capturing in landscape vs portrait orientation to maximize, say, vertical detail in the center of an image? Many of us spend thousands of dollars on better lenses to typically gain less than the 20% difference shown.

OK. Then I understand what you have in mind. I am not sure how much of an issue it is or if better performance in the one dimension is bought at the expense of worse in the other. However, it seems preferable to have an equal amount of blur in all directions and I don't readily see why that shouldn't be possible or why it should come at the expense of something else.

2) Are the dips we see in MTF50 around 1/10th of a second to about 1/300th possibly due to shutter shock - or something else? What implications does this have for people choosing a high resolution camera today?

Hard to say without knowing more about what's going on in DPR's studio. But the shutter speed range affected and the fact that the blur is largely vertical makes shutter shock the likely culprit. The problem is known to occur in that range, with a peak at about 1/100 s or slightly higher. The point where the problem disappears at the upper end of the range may be related to the max sync speed of the camera (disappearing later the higher that speed is). At the lower end, it disappears more gradually, without much of a clear cut point.

That said, it surprises me to see the shutter-shock problem (if that's what it is) appear so clearly in the DPR studio scene samples. Presumably, they use a heavy studio tripod and the focal length is not all that long (about 100 mm EFL). Furthermore, one would at least have expected DPR to take the precaution of using anti-shock delay with Oly bodies and the electronic shutter option with Pany bodies. But I certainly wouldn't have expected any clear shutter-shock problems even if they didn't, provided that my assumption about good tripod support is correct.

The A7r and the D610 show signs of dips around there as well, and they are the lighter of the four FF bodies shown.

Yes, there seems to be a correlation with body weight. How strong that correlation really is (if it is shutter shock we are actually talking about) and why it is there is not yet clear to me. Sure, a heavy FF camera has more weight to "absorb" the forces and momentum associated with the acceleration and deceleration of the shutter blades than a light MFT camera. However, an FF camera is also likely to have heavier shutter blades (four times heavier than an MFT camera everything else equal) and these blades also have to be nearly twice as fast to reach the same sync speed (since they have to traverse an opening that is nearly twice as high). So if we start relating the forces and momentum associated with shutter action, an FF camera is not necessarily better off in this regard than an MFT camera. If anything, it might be the other way around.

Possibly some of this is surfacing now exactly because the better technique and smaller sensors are no longer hiding imperfections that before were below the 'noise' floor. I wonder if anybody ever put a camera through such rigorous scrutiny 30 years ago

Better opportunities to see what's going on probably plays a part here. So does the fact that there is currently so much talk about the problem of shutter shock (if that is what we are seeing here), at least in the MFT forum. More talk generates more attention which in turn generates more talk.

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