Weight would not be a factor for me since the bulk of the weight is potentially in the lens (super or long zooms, or very fast primes), not the camera body.

Size is not an issue - I want a decent size camera to grip especially with the larger lenses.

So for me size and weight are a wash-out issue.

Gains - less noise and vibration (look Ma, no mirror!), faster fps (no mirror latency), see results of exposure changes immediately.

Losses - less battery life (900-1200 vs 300-400 shots full charge), no OVF (yes this is an intrinsic minus as some just don't like an EVF).

Keeping the camera dimensions would mean all current lenses would work fine, no need to design a new lens line (a major investment and risk factor for both Canon and Nikon). Reducing the flange to sensor plane distance would only make the camera a *little* thinner - not a big advantage - and necessitate a new lens line and adapters (yuk!).

Thank You Everyone,,,This has been an informative, entertaining and amusing ride…years ago I got caught up in one of the firearm or military forums in the debate on iron sights versus red dot sights…As an ex combat soldier who has seen a couple of dozen firefights longest lasted four hours most were extremely short and violent affairs lasting only minutes instead of hours and as I cut my teeth on iron sights I was totally against red dot sights as were many others,,,battery could fail at a life saving moment,,,electronics could fail at a critical time,,,the sights themselves could fail and were not as robust as iron sights…I and the others who I sided with were proven wrong,,,hand a rifle with a red dot sight or a low magnification scope on it to a newbie and tell them to put the red dot or the cross hairs on the target and pull the trigger, almost no learning curve, anyone can do it and the sights have proven themselves in combat in reliability and faster and more accurate target acquisition…old habits die hard I still have iron sights on almost all my rifles with scopes or red dots. Most of us are probably of the old school thinking mechanical reliability is greater than electronic reliability and I love prisms and mirrors and optical viewfinders and the quality of Nikon and Canon and Zeiss and Leica and Swarovski glass but the times they are a changing and probably someday the total benefits of an EVF will outweigh the total benefits of an Optical Viewfinder….I guess at that time Canon and Nikon will jump in with both feet…

I am not an Engineer or a Scientist…but it would seem to me that Nikon and Canon could just take their recent models like the Nikon D850 and the Canon 5D Mark IV and offer a mirror less version of each…in the mirror less version just taking out the Mirror and putting in an excellent EVF….the Flange Length could be kept the same so all current Lenses from Both Companies would work without any kind of adaptor and the EVF would read off the sensor or a bank of sensors of it's own…I don't see any reason for Canon and Nikon to develop a separate line of mirror less Cameras and Lenses as the lenses for Full Frame and Crop Sensor Cameras have to be relatively large to cover the sensor and a large camera makes it easier to handle those lenses on camera….also You really do not get that much smaller and lighter in mirror less unless You go to Micro Four Thirds or the Nikon 1 System Cameras with the one inch sensor ,,,So Why not equip current models in the Nikon and Canon line up with the option to buy the Camera with an Optical Viewfinder or an EVF ???

You do know that your information and experience is from 2011? Sony that had one of the worst EVF back then even....

Technology changes... Today you need to test Fuji GFX or Panasonic G9 for EVF.
Year ago it was Olympus E-M1 II or Leica SL.

Next year it might be Nikon or Canon.

If someone keep their opinion based to over year old technology, then they are talking with wrong information. If they haven't gone and tested all features for a month and searched the functions, then they don't know what they are missing.

EVF is far more than just a scope. It is tool to increase productivity by guaranteeing more correctly exposed and focused frames, less praying and guessing, and even more creativity as you can limit your view to effects like black and white or time flow (aka long exposure simulation).


Many still hates tilting screens, yet eventually they learn that fixed screen isn't good.
Many is afraid that their screens gets scratched, until they learn about new coatings and glass.

They say, old dogs doesn't learn new tricks...
But old dogs should as well stop talking about new tricks as they don't know about new tricks....

Everything in past was better, even when it was worse... Because people generally don't like changes....

For years now, about since 2009 the AF has been faster on mirrorless than even best DSLR.
Battery lifetime is longer definitely when camera is required to be turned On all the time. But mirrorless actually has more frames per battery when counting how many you can get. As mirrorless battery time is time based, when DSLR battery is frame based. Mirrorless shoot 7000-15000 frames with a single battery, while DSLR limits to about 1500-3000 frames when in continuous shooting. CIPA testing is time based instead frame based and it even use bundled flash in full power for some of the shots. That testing is not useful for anything else than pocket cameras with electronic zoom, for what it was designed.

And DSLR live view via LCD totally doesn't have than only that benefit, frame via it.
EVF is that you get the viewfinder benefits as low light, bright light and other fast situations better than any OVF. Then all other benefits from focus peaking, magnification, visual effects, face recognize etc is there. The only real benefit OVF has is to use it with long lens as spotting scope for long times. That is what wildlife photographers require for weeks. Sit somewhere, spot and observe. When situation comes, turn camera On and....

Mirrorless requires that moment a binoculars, good vision or more batteries.

The challenge has been to get just old minds turned, realise that DSLR time has gone.