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| Left to Right: Physical size differences between the Olympus E5 (traditional DSLR with optical viewfinder), OMD-EM5 (Mirrorless with electronic viewfinder) and Pen EP5 (Mirrorless without viewfinder) |
In the first part of this series (read it here) I discussed the size of sensor as a critical factor in deciding what camera to buy. I’m now going to look at the viewfinder as the next tick box in deciding what camera to opt for.
A few years ago the Four Thirds conglomerate (being Olympus and Panasonic) brought out what they called 'Micro Four Thirds' by removing the mirror from the camera. This meant that the optical viewfinder had to be done away with entirely. Thanks to digital, users could now see the image directly on the camera’s LCD screen. This meant for a considerably smaller and lighter camera than photographers were used to, while retaining most of the functionality of a full sized DSLR with optical viewfinder.
Fast forward to 2014 and there are three variants of interchangeable lens camera (see the image above with the three different types of Olympus camera): those with an optical viewfinder (ala traditional film cameras, referred to as an OVF), those without any viewfinder and those with an electronic viewfinder (some of which are removable). For some photographers, mirrorless only became a serious contender to the DSLR throne once electronic viewfinders (EVFs) were introduced. Prior to this, mirrorless cameras like the Sony NEX5 and the Olympus Pens were secondary cameras, brought along as an extra body or walkabout plaything. Once EVFs were introduced photographers like Trey Ratcliffe of ‘Stuck in Customs’ began to use them as their primary cameras. Image quality is as good as traditional DSLRs (when comparing like with like in terms of sensor size) but at a fraction of the size and weight and often also at a far lower price point (there are fewer moving parts in a mirrorless camera, meaning less expense in the manufacturing process). The downside is that it takes some getting used to looking at a screen rather than through the lens. This can become irksome in low light when the viewfinder can get quite fuzzy through digital noise and is next to useless in some nighttime situations (forget about looking through the lens if you are trying to peer at stars at night for an astro photograph).
The other major downside to EVFs is battery wastage. Because the viewfinder draws power continuously the battery lasts for a shorter period of time than in an optical viewfinder camera (about a half to a third as many images as with traditional optical viewfinder cameras). This is worsened by the fact that the small form factor of the mirrorless cameras means that they are often equipped with wimpy little batteries. To add insult to injury, manufacturers like Sony now don’t even include a battery charger with some of their cameras (the top end A7 and A7r cameras are glaring offenders in this). This means that on top of getting poor shot to battery usage, users must also charge the battery through the camera unless they buy a separate battery charger at additional expense.
Having, or not having, an optical viewfinder becomes one of the central choices when selecting a camera. This also plays a role in selecting from Sony’s crop of ‘traditional’ DSLRs as they are now all equipped with a semi-translucent pellicle mirror. The mirror is only there to assist the auto-focus sensors while the viewfinder is in reality and despite appearances, an electronic version. It seems that this is course that Sony are commited to at the moment, so don't expect OVFs from Sony if you decide to buy into their system.
The OVF vs EVF or none at all debate is complicated by the fact that autofocus is severely affected by the loss of the OVF. In most DSLRs the core autofocus sensors are situated in the prism housing of the camera and off to the side of the mirror box. These sensors are able to measure focus while the mirror is in a stationary position and lose focus as it travels up and down during the actual exposure There are fancy algorithms in the cameras software to make up for this loss). Only the Nikon 1 series V cameras and Canon’s 70D come close to matching the autofocus performance of traditional OVF DSLRs (and the Canon although accurate is not as fast). If autofocus speed is a consideration, then the choice between an OVF or EVF camera is a critical one.
Eye strain is another factor to consider. First there is the issue of flicker on the screen. This is almost non-existent in the current crop of EVF cameras, but is something that I have heard users complain of when EVF cameras first started to appear. The argument also isn’t as clearcut as simply saying electronic devices cause eye-strain and optical ones do not. In OVF camera the actual magnification factor, brightness value and diopter settings are also going to play a role in eye-fatigue. The bigger the magnification the less work your eye has to do when looking through the viewfinder. The same applies for the brightness of the viewing screen (one of the conspicuously absent specifications in marketing literature in my opinion - and before any reader get on their hobby horse that brightness is affected by the maximum aperture of the lens used, the brightness is also affected by the different types of glass and plastic in the ground viewing glass that sits beneath the prism - In the days of interchangeable ground glass you could buy brighter screens, or screens with different etch marks and fresnel patterns to make focusing easier).
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| A roof prism as used in DSLRs which flips the image around so that the orientation in the viewfinder is the same as that which we perceive. |
To make life even more complicated there is the difference between a prism finder and a pentamirror finder. A pentaprism is a lump of glass that the reflects light internally so that the image we see in the viewfinder is correctly oriented (not upside down and back to front). Interestingly DSLRs don’t actually use a penta-prism, despite their marketing literature. They actually use a roof prism. The point though is that the traditional prism that sits on the top of the camera is made from a solid piece of glass. This transmits light efficiently so allowing most of the light that enters the prism to be refracted through it. A pentamirror on the other hand is an empty box shaped like the traditional roof mirror but with internal walls of reflective mirrors. The advantage is in the actual manufacture of the pentamirror. It’s cheaper. However, pentamirrors tend to be darker in viewing (the number of mirrors mean that transmission of lights isn’t as efficient) and have a lower magnification than glass prisms.
Of course Full Frame once more crops up when discussing viewfinders. Since the actual sensor is physically larger than APS-C, it stands to reason that so too would the internal mirror be larger. This means that a bigger image enters the prism, which also has to be bigger, and the result is a larger brighter viewfinder. No surprise then that photographers using full frame cameras for prolonged periods of time complain less of eye fatigue than those using APS-C sensor cameras. Of course looking through the big bright viewfinder of a medium format camera is an experience in itself.
New EVFs are sometimes bigger than their pentamirror cousins, so looking through a Olympus OMD EM-5 can actually be easier than looking through something like a Nikon D3200. EVFs also have the added advantage of ‘focus peaking’. This is a technology from the video industry that highlights areas of fine contrast in a noticeably visible colour (usually red, green or white) in the viewfinder. This supposedly makes manual focusing considerably easier.
As ever, the plethora of choices makes choosing a camera bewildering. However deciding on whether a viewfinder is essential or not can literally quarter the number of potential cameras. In the next article I'll discuss build quality and controls as selection criteria. In the interim, drawing up a table with costs, sensor size and viewfinder options will already narrow down camera choices from a seemingly impossible number to decide from.
Read part I of choosing a camera at: Decision, decisions, decisions - part 1 of choosing a new camera
Continue with part III at: Bang On - Build Quality and Ergonomics - Part 3 of Choosing a New Camera
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