A Pro's opinion of EVF vs OVF

Started May 30, 2013 | Discussions thread
chlamchowder
Senior MemberPosts: 2,056Gear list
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Re: Why the writing's not on the wall (and the new link)
In reply to photoreddi, Jun 1, 2013

Like it or not, the EVF doesn't have to approach the speed of an OVF. It only has to be fast enough so that its delay is imperceptible, faster than the human eye, brain and their chemical pathways. In a couple of years much faster, less expensive EVFs should be available. One DSLR delay that won't get much shorter after those years is the inter-frame blackout due to the mechanical limitations of the mirror.

We'll talk about that again when it gets there. Right now, it's pretty far off, especially in low light.

I suspect that the inter frame blackout won't get much shorter for EVFs either. For every increase in processing power, there's a corresponding increase in data (megapixel count) that limits the speed advantage we see. Why does the D800 not do 8 fps? Its shutter, mirror, and AF system (from the D700) is certainly capable of that.

The EVF inter-frame blackout comes from the readout speed of the sensor. You have to read out the frame being exposed, and then switch quickly to reading off low resolution frames to keep delivering live view. This process is so inefficient that no EVF camera, including the a99 and a77, can even offer live view between continuous burst frames when shooting faster than 3-4 fps. Is it possible for it to compete with OVFs in the future? If the megapixel race stops, yes...

Smaller sensor cameras may have a DoF advantage, but it doesn't help or hinder AF accuracy. The PD AF sensors act as mini-rangefinders, and in Nikon's DSLRs they use the f/5.6 part of the lens, so f/2.8 lenses don't necessarily focus any more accurately. They may (or may not) focus more quickly, but that's due to a completely different part of the lens design, including mechanical, electronic and algorithmic differences. The AF accuracy is what it is, evaluated at the subject's distance from the camera, not at any distance between an artificial DoF's near limit and far limit. With your V1 vs FF examples at f/5.6 and f/16, the DoF at 30 ft. is a bit under 3 feet for both cameras. The FF camera will focus just as accurately (ignoring the effects of the lens's aperture based focus shift), whether it's shooting at f/2.8 or f/16.

You miss the point entirely. The huge depth of field given by the tiny sensor and small aperture would cover up any AF inaccuracies. Take any DSLR, stop down to f/11, and track a fast moving subject. You'll easily get about a 100% hit rate in terms of usable shots. What really shows how good an AF system is is how it performs with limited DOF, which requires far better accuracy.

My Sony a580's tracking performance was shaky with a 70-210/4 at 210mm f4. But close it down to f/6.3 or higher, and you're looking at a hit rate approaching 100%. We really haven't seen the V1 with anything like a 110mm f/1.0 lens (close to the standard 300/2.8 on FX), because no such lens exists. And with larger sensor cameras, on-sensor PDAF ranges from slow (Canon 650/700D) to having really limited use (a99 -  points not selectable manually, and don't even work at all with most lens).

EVFs have some disadvantages but so do OVFs. What we do know is that OVFs have for all practical purposes reached the point that they can't be expected to be significantly improved. EVF will keep on improving and just as digital cameras eventually displaced film cameras, EVFs will eventually replace OVFs in all but the cheapest cameras, and even those will eventually fade away. To think otherwise would be just as mistaken as those that loudly shouted not too long ago that film SLRs would never be supplanted by digital cameras.

Another point that I disagree with...

OVFs can be improved and are being improved, but improvements are often slight because they're so good already. With no lag and very little blackout time, they're unbeatable for action shooting. And resolution is already higher than that of any EVF.

And no, it's not like film vs. digital because EVFs offer no new functionality. Want the features of an EVF? Just press the LV button on any modern DSLR. EVF cameras only offer reduced functionality, losing the option of using an optical preview when appropriate.

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