What is equivalence good for?

Started Jul 25, 2014 | Discussions thread
quezra Veteran Member • Posts: 3,915
Re: LX7 wins

jrtrent wrote:

quezra wrote:

jrtrent wrote:

quezra wrote:

Now I happen to want good general lowlight picture of people. So your considerations are irrelevant to mine and I don't want to go much below 1/50 shutter because people can't hold a smile much longer than that. So which camera is the best?

I already gave you my criteria and conclusions, so far as I can judge from online information and restricting it to low light performance. Each user may well be unique in what they want to accomplish, so it's not surprising that my considerations are not shared by you. You've already indicated that you need about a 1/50 second shutter speed as a minimum; go ahead and give us any other criteria you might have and tell us your own conclusions.

The point was you introduced a bunch of arbitrary considerations (e.g. "handholding at 1/4 shutter") which were pretty ridiculous. Imagine someone who shoots lowlight and the most common subject for most people is people themselves. People who shoot still photos tend to be enthusiasts and they would have any number of ways to overcome an arbitrary restriction like handholdable at 1/4.

Your original question did not include any shooting conditions, just, "You want to buy a nice camera with good lowlight options." The most common low-light condition for me is museums, where I might want pictures of a few of their displays, and neither flash nor tripods are allowed. If one camera's image stabilization allows sharp pictures at 1/4 second, then that's an advantage for me over one that needs 1/10 second. Naturally, if your shooting requirements require 1/50 second as a minimum, then slower shutter speeds are not a consideration.

No the most common way to approach it is to assume that any unstated conditions should be held equal across cameras.  Instead, you introduce arbitrary values based on subjective ratings of "camera shake" which are pretty ridiculous to begin with, worse still when your "idealized" shot means shutter speeds so slow it can't have anything moving faster than a tree in it.

So if I were to ask, I want to shoot common subjects (e.g. me and my friends in a bar) in lowlight and I'm looking at LX7, X20, RX100M3, GM1 kit, and A5000 kit, what can I use to compare their performance aside from equivalence?

If you look at an exposure chart, you'll find that three factors determine the light levels you can shoot at: shutter speed, aperture, and ISO. Each person has to figure out what their needs are for each. You've already determined that your minimum shutter speed is 1/50. For each camera, you also need to decide what is the widest aperture that is both available and useful for you. On zoom lenses, that changes with focal length, which is why I mentioned that I like a 50mm equivalent; your needs may be different. Also, even if, say, f/1.8 is available, you might not want to shoot it wide open (e.g., the lens might need to be stopped down to avoid too shallow a depth of field for you, or possibly image quality falls off more than you like due to reduced contrast and sharpness when wide open).

You notice that I said the best photos.  I use the simplified language of someone who doesn't know cameras well, but the "expert" giving advice should know to understand these as making them equivalent, not to arbitrarily introduce silly conditions in order to sell their prefered brand. That's calledd being a huckster, not giving sensible advice. Does ISO 800 and ISO 1,600 look the same across all formats?

You also need to figure out where each camera lands in terms of the highest ISO you are willing to use to keep image quality you're happy with. This is one area which the recent article on equivalence here at DPR said could not be determined by equivalence formulas due to differences in sensors. I may have picked an arbitrary print size in my earlier comparison, but it showed me that despite the differences in sensor size among the RX100, GM1, and A5000, they all needed the same ISO speed to achieve similar quality for that print size.

I asked for the best.  I didn't ask for what's good enough for you.

And, of course, you need to know the light levels you can expect to run into in the places you want to take pictures. The museums I've been to get down to EV 3 pretty regularly, and many displays are dimmer than that. The bars you mentioned might be similar; I'm not sure since I've never taken pictures at a bar.

Well as I said, I'm just talking about dim conditions.  You are evidently trying very hard to make a "good enough" argument which is why you are trying to find any way you can to make it such that we don't talk about relative performance, but some lowest common denominator after which all cameras pass.  But that means you are only recommending cameras based on idealized criteria of some imagined shooting situation rather than giving sound advice on which one is actually best (since you aren't actually going to be always and only shooting in that one hypothetical condition).

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