Sony A65 & A77 EVF - Copyright (C) Sébastien ORTEGA-DUBOIS - All rights reserved

Sony A65 & A77 front - Copyright (C) Sébastien ORTEGA-DUBOIS - All rights reserved

Sony A65 & A77 back - Copyright (C) Sébastien ORTEGA-DUBOIS - All rights reserved

It may help better understand the differences justifying the very large price gap between the two models (for the same digital sensor).

Pictures coming from a partnership with Sébastien Ortega-Dubois who gives more detailed differences in a comparison of Sony SLT-A77, Sony SLT-A65 and Sony Alpha 55.

What is an EVF?

EVF = Electronic View Finder.

Be ready to see this term used more and more, even for SLR cameras. Many a compact point-and-shoot photo camera already is equipped with an EVF, but it is most common in video cameras (and it has been for many years already). In the viewfinder, instead of looking at an image coming from a more or less complex optical system, your eye is pointed at a small LCD screen (or TFT, or OLED or whatever similar technology) reproducing the picture recorded by the CMOS imaging sensor of the camera.

After all, this is only what we already know well as the LiveView mode on the back LCD of nearly all the compact photo cameras (and many SLR too). But as a small picture in the viewfinder.

An LCD display + a viewing lens = an EVF.

In some case, you could add a small mirror for space reasons, but this is a minor variation to the original tune.

EVF and Single Lens Reflex (SLR) cameras

SLR viewfinder

A Single Lens Reflex (SLR) photo camera is organized around a very mature technology in which a mirror reflects the image through an eyepiece via a pentaprism (or a penta-mirror) as in the drawing on the left.

Of course, as the film (film plane and focal plane shutter) is hidden by the mirror, this one must be drawn up to take the snapshot.

All this is greatly simplified when there is an electronic viewfinder.

Advantages and drawbacks

Advantages et gains from an electronic viewfinder

The first positive side is mechanical and optical: If you remove the mirror and the pentaprism, the architecture of the camera will be greatly streamlined, lightened and its manufacturing cost will go down. For three different reasons (at least):

• reduction of the number of parts
• reduction of the assembly complexity (or of the amount of human work needed)
• increased ease of calibration (alignment) of the optical parts (an LCD and an eyepiece, rather than a whole bunch of parts)

Even better, the disappearance of a huge articulated and mobile mechanical system brings several positive effects:

• increase of the continuous shooting speed/cadence (there’s so much less hardware to move around for a photo)
• reduction of shutter noise (in a traditional SLR camera, most of the noise actually comes from the mirror up-swing and the shutter operation; It’s worth removing one of them)
• a lighter mechanical structure through reduction of the quantity of parts and since the enclosure is lighter because it has less stress to sustain in all these shocks and moves

Also, the electronic viewfinder exactly reproduces what the sensor sees. A 100% optical coverage on a viewfinder of fully optical design has always been reserved to the most expensive SLR cameras. But when you get an EVF, 100% coverage is totally natural and effortless. Luxury comes to you in the clothes (and price) of entry level.

Then, having an LCD display brings the additional possibility of adding all the data you can think of. Many brands already experimented with this and brought us some Electronic Viewfinders with features like:

• Histogram
• Artificial Horizon
• Zoom on a part of the image
• Telltales and technical displays (aperture, speed, ISO, etc.)
• Active AF zones (including face detection)

Fuji	Fuji X100
Sony Alpha SLT-A77

As a matter of fact, there is no other limit than what a computer screen can display: Data, image, etc. It’s only a choice from the designer.

And it’s not even the end of it. The EVF also has a major advantage when light is low: As far as the sensor can see something, it’s only a matter of amplifying light signal (like for the ISO sensitivity selection) to make the picture readable. If the photo is possible (even barely possible), showing it is possible. Think about it! A nikon D3s digital sensor could display what it sees even in the darkest dawn it can manage. Since the digital noise is only a marginal issue on an LCD display (even at 3MP resolution), you can see what the sensor will be able to grab even in a room too dark for comfortable framing with an optical viewfinder.

If you compare it with the lowest-priced optical viewfinders of entry-level SLR cameras, the EVF is an easy winner in those low-light conditions: These simple viewfinders where already unpleasant and dark, the EVF bring a new life to cameras used indoors.

Drawbacks and limitations of the electronic viewfinder

But all is not pink and shiny. EVF have the same problems as most point-and-shoot cameras find on the rear-side LCD displays used for LiveView.

To start with, even if the electronic viewfinder (EVF) is intrinsically better protected against sunlight, it is still very sensitive to bright light issues. If there was only one thing that the EVF-sensor pair does not like, this would be high lights and bright sun (sic!) highlights are easily washed white and overblown. You will find more white flat areas than nice clear zones. The worst comes when you add high contrast to the picture. The EVF has a very small dynamic range (this is not HDR!) and the designer must choose between high-lights and dark areas.

We tend to forget it, but the human eye is amazingly sensitive and adaptable. Behind a prism and a mirror, in the brightest mid-day sun light, it can marvelously adapt to over-exposure situations that totally saturate the purely digital EVF system.

Best (or worse), the eye is extraordinarily able to switch within a few hundredth of seconds from the darkest night to the most violent lighting without even thinking about the marvelous brain processes involved. On the contrary, the EVF system uses a gain correction which will change at any time the apparent brightness to track the actual scene brightness. What is clearly an advantage in a dark room, forces the system to include an auto-adaptation feature which will change the brightness of the EVF several times per second. According to what you point the camera to, the electronic viewfinder will change from lighter to darker display. Not really a problem, but this asks for some tolerance to a process which is not natural to our human eyes. You have to get used to it.

Additionally, but this is all very sensitive to the user (you!), watching a computer screen may be more or less comfortable in the long run. As a matter of fact, if you use the EVF for long hours (this is the case for the professional photographer waiting in front of the Cannes Festival stairs, for the photo safari amateur or for the intensive tourist photographer willing to bring everything on a memory card – don’t laugh, I’m sure you shoot it as much as I do), you may come back with a serious headache. This is certainly not an issue for everybody (and you’re not supposed to keep the camera to your eye if you want to immerse yourself in your subject), but this may become a real limitation to some people. At the strict minimum, you must take very seriously the setting up of the dioptric correction of the eyepiece (much more seriously than on your current camera) to limit the impact to a tolerable level. Unfortunately, the eye seems to get more prone to this issue when the photographers gets older… Our eyes are not equal in front of photo gear. Too bad, but true.

Sony Alpha : miroir semi-transparent et EVF

Last but not least, even if the electronic viewfinders improve in time (and Sony has shaken the market with a 2.3-million-pixel EVF in the Sony SLT-A65 and in the Sony SLT-A77 which has raised the bar to a whole new level for all the competition), the fine quality of a focusing screen in a common optical viewfinder stays incomparably better than what the best EVF can display today. Far better! This is the reason why they generally include an additional Zoom feature allowing to better judge focus through enlarging an area (On the opposite, a company like Zacuto proposes an enhanced edge sharpening to make the focus analysis easier or more natural).

If you let your camera focus for you, honestly, you shouldn’t care much about this. If you like to fine-focus your pictures (all the more if you use a USM, SSM or similar lens which allows easy manual focus correction), if you use wide-aperture lenses (which call for a very attentive selection of the focus location or AF area), you will be in a living hell playing with buttons to merely focus while you were used to just looking at the image in your old optical viewfinder. Interestingly, Sony keeping in its technological portfolio the marvelous AcuteMate focusing glass surface (bought from Minolta and still widely considered as the absolute best here), is the first to jump to the next technology.

While we talking about AF, we must stop and remind ourselves that the disappearance of the reflex mirror means that focusing is now done from the data directly available on the image sensor. Where the traditional SLR camera focuses just before the exposure, using phase difference sensors (high precision, high speed, and not very complicated), the EVF viewfinder seems to enforce the use of automatic focusing using the measurement of a contrast difference directly on the image (very consuming in terms of processor power, intrinsically less reactive). Sony, once again at the forefront, chose to insert a semi-transparent mirror to keep the fast phase detection sensors. But they are quite alone in this decision – for now.

(Temporary?) conclusion

The electronic viewfinder is no panacea. But it brings good answers to tough questions asked by the old reflex technology, starting with price reduction for the digital photo cameras which is always a major issue for the manufacturers.

The camera owners already used to the optical viewfinder of entry-level cameras will immediately recognize the many advantages and all the more if they are occasional photographers or if they come from the compact point-and-shoot camera world.

Expert users (not even pros) will certainly have more mixed feelings, even if the most advanced electronic viewfinders like the recent Sony ones progressed in great strides. As I read in one of the recent articles about these new photo cameras, Sony brought enormous (not incremental) progress but this is still an electronic viewfinder. Not perfect, but with enough advantages to balance the drawbacks.

Now, you may have to read the post again to choose which ones are the most important for you. But there is a big problem left: We usually choose our photo camera inside a relatively dark shop (perfect, ideal conditions to demonstrate an EVF) and we use it mostly during our Summer holidays (the worst conditions to use an EVF). Some people may be unpleasantly surprised if they do not think twice before choosing a camera.

Sony Alpha 33

Sony is also announcing that some of the new features of the Sony Alpha 35 will be made available for the older Sony Alpha 33 and Sony Alpha 55.

• Support for the ‘Picture Effect’ function featured on the new α35
• High-Speed Synch is supported during wireless operation with a compatible external flash (α55 only)
• Revised menus and a new mode that lets users switch shooting parameters overlaid on-screen for clear, uncluttered composition
• The a33 and a55camera’s Digital Level Gauge can also be displayed when shooting via the optional CLM-V55 external LCD monitor
• Frequently used features can now be custom-assigned to the D-RANGE button for rapid, menu-free access

To be downloaded as early as June 20 from http://www.esupport.sony.com.

Sony press release in a word cloud

Most of them are for the Sony Alpha 55. Many reviewers have been attracted to this innovative photo camera.

DxOMark - Sony A55-SLT at the top

It is clear that Sony has impressed a number of the users with its Alpha 55 (A55-SLT). Despite the very legitimate concerns about the length of video sequences, the camera seems to be appreciated a lot by all the evaluators. The latest and possibly the most impressive (or the most telling) is the recent evaluation of sensor/image quality by DxO Labs in DxOMark.

Actually, the Sony Alpha 55 appears as the best APS-C from all the competition even with splendid cameras like Canon EOS 7D or Nikon D300s.

Today, I’ve got a rather detailed talk with Édouard Schmitt, Sony France Alpha Product Manager, who helped me go over the current situation created by the announcement made by Sony a few days ago when they revealed that the digital sensor of the Alpha SLT-A33 and Alpha SLT-A55 could meet some over-heating issues (see our posts about it here).

As expected, he confirms us the information provided previously: The use of the video capture mode leads the digital sensor to heat up to the point where, after some time, the camera will decide to switch itself off (some kind of “thermal circuit breaker” kicking i, if you want).

What is more interesting is the overall presentation of the issue: “This is not a dysfunction of the sensor, but an auto-protection“. Furthermore, Édouard Schmitt went into the detail of the causes and confirms (and precises) the evaluations I could have provided here before:

• The image stabilization (which, for Sony as well as Pentax, operates by sensor displacement) produces some heat inside the camera,
• The sensor itself is a heat source –like any other electronic device– when it is used continuously like during video capture,
• The external temperature is also an important parameter in the equation (As a matter of fact, in the table provided here on the right, we see that the higher the external temperature, the shorter it takes for the sensor to overheat).

I noticed that sony insists heavily on the fact that image stabilization is a major factor here, from two different angles:

1. It has a primary impact (It’s true that the useful shoot time is (more than) doubled when not using SteadyShot)
2. This is the only solution offered by Sony; E.Schmitt excluded the possibility of a future firmware that could improve on the current status.

Nota bene: The observed maximum figure of 29 minutes comes from the normal recording limit of the camera as it is more or less forced upon us by fiscal regulation (a camera able to record longer sequences is heavily taxed in some countries and Sony decided like other manufacturers to stick to this limit for mere reasons of cost).

Up to this, the message is relatively simple but some important elements are added by Édouard Schmitt. First and foremost, the cooling down process is very fast and a few seconds only are needed to obtain a few more minutes of video capture (some real-life tests will obviously be needed to quantify such a statement, but it seems that the Sony user will not forced to watch the camera cool down indefinitely).

Then, and it should be checked and confirmed, “it’s not better elsewhere“. Understand: Sony’s competition has the same kind of issues but they do not communicate much on it. [Ed: I'm still wondering what is the influence of image stabilization here]

As a matter of fact, according to E.Schmitt, “90 or 95% of customers first buy a photo camera [and for them] a 3-, 4- or 5-minute take, it’s already long“. In fact, those who have a longer need are not in the consumer market anymore and the impact on the sames of the Alpha 33 and Alpha 55 will be minimal. It is even suggested that “in the future generations” the issue will be taken with a different kind of attention (Ed: Here I cannot stop thinking about a future, possible, probable, Alpha 77).

The last two subjects that we discussed were relatively lateral or complementary (but the YLovePhoto readers know that this has been discussed here in the past): LiveView mode and the NEX family of cameras. On the one hand, I could not obtain any statement on the effect on continuous display on the back LCD of the photo camera, other than a bland comment on “it’s rarely continuously used.”

Copyright (C) Muffet

For the NEX-3 and NEX-5, there is no trouble here. They are not impacted by the issue. First and foremost because their image stabilization is not obtained through sensor displacement, but by the action on an optical group inside the lens (thus, one of the causes mentioned above disappears). The smaller size of the body is also participating by providing a much better thermal exchange with the external air and allows to keep the internal temperature lower.

But there was a fly in the ointment. Only a few weeks after the official launch, we learned that the digital sensor is overheating. We know that the digital photo-video sensors produce heat whenever they are used. The design of sensors for video (and thus used more or less continuously) must take that into account to avoid heat production at all costs. The design of the cameras must take into account the need to move any heat left right out of the sensor area (possibly out of the camera).

Sony definitely missed one of these, indeed. The SLT-A33 and SLT-A55 are suffering from over-heating to the point that, when reaching a certain temperature, the camera switches itself off (It shuts the sensor down). As can be seen in the table here on the side, in the worst case (when it’s hot outside, 40°C, and that image stabilization is enabled), this is going to happen fast, real fast: 3 or 4 minutes only. Probably nearly everybody will admit that this is incompatible with the normal use of video capture in a normal way.

So, no video grabbing during Summer. More or less.

If you thought that this was bad enough, there is a hint to the possible addition, unconfirmed by Sony right now, of another limitation (maybe, within a longer time frame) respective to the use of the LiveView mode (which is only a low definition video mode).

The solutions? Let’s try to think them out:

• No firmware change will reduce the thermal dissipation of the sensor.
• No firmware change will improve the heat transfer through the body of the camera.
• A firmware change could remove (more or less completely) the thermal protection. But would it be a solution to risk some other problems? (early aging of the sensor, unacceptable thermal noise in the images, etc.)
• Modifying/replacing the sensor (supposing that Sony has a better or corrected sensor)? This is going to be a MAJOR repair operation.
• If the problem really comes from a bad design of the camera body, this is worse… Nothing left in the bag of solutions.

I let you imagine Sony’s dilemma. I let you imagine why the communication will be really tough next week…

While waiting for it, for those asking if they should buy a Sony SLT-A55 and thinking that they need the video capture, I say: Wait. For those who are in a hurry, I will not less than they must forget about video on the Alpha 33 and Alpha 55 for now. Video is nearly excluded in these cameras for the time being. The small sound you can hear is those competitors (Starting with Nikon and Canon) exhaling loudly (These cameras had given them cold sweats and they now feel that this could buy them some more time to react).

After a few minutes of use (mostly in video mode, but possibly in LiveView too), the sensor will overheat (effect is unclear). The best (albeit partial) solution is to stop using the Image Stabilization. As you can see in the table above, it increase the time available.