Sorry, but I can see FAR more dynamic range with my eyes than my camera sees. Whether it is my brain blending "frames" to achieve it, or individual exposures...the mechanics of how don't matter. When people say 8-11 stops is similar to 10-14 stops, they are ignoring the fact that a stop is factor of two. It's a difference of 8 to 64 TIMES greater tonal range. My eyes see at a minimum 14 stops...from clouds to bark detail in the shadows, which is probably closer to 20 stops than 14 stops. It doesn't matter that my brain is "doing all the work" to blend the information the biological device that is my eye actually receives...I SEE it.
Now, I don't say my eye can see unlimited DR. However an optical viewfinder is not going to limit you further. The OVF itself is effectively unlimited when it comes to DR...so my eyes can operate at maximum capability when looking through an OVF. When it comes to shooting in lower light, with my eye to the viewfinder, being able to utilize the full 24 stop dynamic range potential of my eye...i.e. allow it to adjust to the dimmer light so I can clearly see my subject without noise for the purposes of framing and composition, regardless of whether my camera could see the same thing when read out at 60fps, is a huge boon. Jack up the gain on an EVF or Live View...and what do you get when it comes to darker scenes? Dark...with a lot of noise. This problem is even exacerbated further when doing something like astrophotography...you can't see the night sky in an EVF or on Live View. You might be able to see some of the much brighter low magnitude stars, but overall you can't compose. However I can look through an optical viewfinder and see everything as if I was looking right up at the sky without a camera in front of me. The dynamic range of the human eye is VASTLY superior to the dynamic range of a camera (and an EVF.)
If you're doing landscapes I really don't think the limitation actually hinders anything, since you're going to be looking at the scene quite a bit before you ever lift the camera to your face (or set up a tripod, which only furthers my point). At which point seeing what the camera sees is only a shortcut to making a proper exposure.
In action, are you actually adjusting the exposure moment by moment to match the changing conditions? I've never heard of anyone actually doing that (I usually hear about sports shooters using aperture priority, giving most of the control to the camera anyway), but if anyone does sit there with their finger constantly whirling the control wheel back and forth more power to you.
Low light, ok you got me. Playing around with the 5D2 in live view just now, it was pretty limiting. The pictures turn out a lot better than what I can see, but the live view implementation is lacking. I have to think that some tweaking would fix that though.
I should also note that my naked eyes were still much better than looking through the OVF.
I'm still grasping for a situation where the dynamic range of the OVF is a critical aspect of capturing a photo.
Sorry, I guess I wrote my prior response in a way as to be misinterpreted. It isn't so much the dynamic range of the OVF. Technically speaking, it doesn't have dynamic range, it's just an optical light path. The point is that it does not LIMIT dynamic range...where as EVFs most certainly do! There are two factors that limit DR in an EVF. The first is the dynamic range of the sensor...whatever the sensor is limited do, whatever you see on the EVF is limited to that as well. Furthermore, as EVF pixels have shrunk, it seems to be more difficult to extract much dynamic range out of them as well...it seems that shadow tones are particularly difficult to replicate when EVF pixels are even smaller than sensor pixels (under three microns for some of the higher resolution ones.)
I won't discount the possibility that a better way of emitting light from micron-sized dots may come along. If and when a technological improvement does come along that is demonstrably better than current technologies, I'll reevaluate my opinion. To date, the kinds of screen technologies that allow for small pixels don't quite seem up to the task of developing micron-sized pixels. They do much better when pixels are several hundred microns, such as in high density smartphone screens.
Even assuming some new technology does come along, there is the whole resolution issue as well. I have 20/10 vision with my glasses or contacts. When I use my contacts, the 1" (or often less) eye relief of an EVF in a mirrorless camera is short enough that I can CLEARLY see the pixels. I HATE that. Aside from the quirky tonality/DR issues that I've seen in the kinds of EVFs that are currently being used in mainstream mirrorless cameras, the pixellation is the absolute worst. I did the calculations here before...for 20/10 vision at 1" eye relief, you need 12,000ppi in order for pixellation to become invisible. That is a pixel size of 700nm, and a light channel size even smaller than that. Your filtering out visible wavelengths of red light from around 680nm through 750nm and all IR. It would be impossible to reproduce accurate color that way.
So even assuming EVF's reach a technological pinnacle where they are otherwise superior to EVFs...for anyone who has 20/10 vision (which is a LOT of us, given how many people use corrective lenses, and how eye docs strive to find the best fit for you...at least, my doc does and she sees several thousand patients a year for regular checkups, a regular checkup is every two years, she is one of six eye doctors in that facility who all see similar patient loads...do the math, LOT of people), anyone who has 20/10 vision will be stuck looking at pixellated EVFs. When I look through my 7D OVF with its Transmissive LCD...I can see the pixels of the LCD, but because of the optical design, all that stuff just kind of fades into the background. You don't look at the TLCD...you look at the real image projected through the pentaprism. The effect is only magnified when you look through a 5D III or 1D X viewfinder...larger, clearer, crisper...and the TLCD pixels are even smaller relative to the viewfinder frame size. The aesthetic appeal of what I see through an OVF is vastly superior to what I have seen through EVFs. There is no lag time, no flickering of any kind, everything is nice and bright and crisp and clear, everything is highly detailed, color is quite rich, and I STILL have an active and useful HUD (and I can only hope Canon's Hybrid EVF takes advantage of their TLCD, making it even more useful for general purpose OVF stuff.)
When it comes to landscapes, I don't even care about an OVF or an EVF. I care about the LCD screen. The bigger the better, as I always use my DSLR in "field cam" mode with live view on. This is one of the reasons I appreciate the rumor that the 7D will be getting an even larger LCD screen...I think Canon's current ones are 3.2"? That means the 7D is going to be 3.4", maybe larger. THAT is what I care about for landscape photography. I can only hope that a huge LCD screen like that makes its way onto whatever their big megapixel camera is...would be superb as a landscape camera.
As for changing settings while photographing action. I don't change settings WHILE PHOTOGRAPHING action, however I quite often change settings in between bursts as I see lighting change when tracking a bird. I'm not nearly as good at it as I wish I was, and I hope to get much better at it, but when your tracking a bird that is moving such that the angle of the sunlight on it changes, you have to react. You can't leave your settings be and hope for the best. I usually start out with the bird broadside to the sun, but as you track, especially when the bird is flying at an angle slightly towards you across your view, the distribution of light and shadow changes. You have to protect the highlights, and that means changing exposure while tracking with your eye pressed up against the viewfinder.
Now, having tried out a few mirrorless cameras, I honestly do not believe I would have accurate enough information responsively enough to deal with such a changing DR scenario real-time, without moving my eye from the viewfinder. For one, no matter how good the DR on the EVF, the image you see there is processed to one degree or another, so the contrast does not represent reality. Even if you had an exceptionally high response rate, you would never know for sure whether what your seeing actually represents reality or not...you have to guess. When the birds highlights look blown on the EVF...are they really blown? I don't have any visual or digital cues to tell me this for a fact with an OVF...but I have developed an instinct for it, because I have REAL information to work with...I am seeing something that actually exists in reality, not a replica of what might exist in reality.
So...I'll grant, perhaps, maybe, someday, an EVF will come along where I don't have to even think about these issues, these facts. Maybe someday an EVF will come along that gives me information that is as good as the kind of real information I work with now. That day has not yet come, and I know enough about the technology ad the scale it's being designed at to honestly wonder if it could ever get as good. My suspicion is EVFs might start offering visual cues to indicate what you would simply sense, without necessarily even having to think about it, with an OVF. These visual cues would help you make the necessary decisions about changing exposure or whatnot...but I don't think they will ever be as good as having an optical window into the real world. With practice, you can operate largely on procedural memory and instinct without ever removing your eye from the viewfinder. Because you can 100% rely on the information reaching your brain through the viewfinder. That will simply NEVER be true with an EVF.
Call me a skeptic, but, I'm one of those people who will stick with my good ol' mirror slapper until they literally pry it from my cold dead hands (or, until the last OVF camera ever made that I manage to purchase dies some horrible electronic death, and I'm literally left with no other option but to move to an EVF...oh, what a sad day that will be...)
