Single Lens Translucent cameras, such as the Sony A35, Sony A55 and Sony A77, are quite different from traditional Digital Single Lens Reflex cameras. The difference, as the name implies, is in the mirror used in SLT cameras. Let’s take a quick look at how DSLRs differ from SLTs.
DSLRs vs SLTs – It’s all in the mirror
DSLRs have a hinged mirror to reflect the light coming through the lens to the viewfinder and the auto focus. The user sees the scene as seen through the lens and composes his shot. Once he presses the shutter button the mirror flips up and exposes the main sensor situated behind the mirror to the light rays. The sensor records the image and applies white balance, exposure compensation and other settings. The final image is then viewable on the rear LCD screen.
In SLT’s the mirror is translucent and fixed. A certain part of light is reflected up to the Auto Focus sensor while most of the light rays pass through the translucent mirror on to the main sensor. The sensor records images continuously and sends those images on to a Electronic Viewfinder, which the user uses to compose his shot.
SLTs advantages vs DSLRs
- Very fast continuous shooting speeds – Current SLT’s are capable of between seven and 10 frames per second which is almost twice the speed of similarly priced DSLRs. This will be especially useful if you are interested in capturing action shots.
- Continuous auto focus during video – Because of the design of the SLT, the auto focus sensor receives light continuously. This enables the camera to auto focus (using phase detection) even when recording video. This contrasts with DSLRs which lose continuous auto focus capabilities when the mirror is flipped up (for example when recording video). This will be useful if you intend to use your camera for video recording extensively.
- Less noisy with less vibrations – With no moving mirror mechanism, SLTs are less noisy which maybe important when silent operation is preferred. They also have less vibrations and this maybe important when doing landscape photography (in traditional DSLRs you have to use workarounds such as “mirror lockup” to lessen the impact of vibration on the image sharpness).
- More compact – SLTs do not need a mirror mechanism or a prism mechanism (which is necessary for the optical viewfinder used in DSLRs). This should be important to you if you are concerned about the bulk and weight of traditional DSLRs.
- What you see is what you get – With SLTs the image you see when you look in to the viewfinder is your final output. The white balance, exposure compensation and other settings you selected are applied to the viewfinder image. This maybe important if you shoot in JPEG and getting the white balance correct the first time is important or if you want to see in real time how the final image changes when you change certain settings. Also more information can be superimposed on to the viewfinder image such as a histogram.
SLTs disadvantages vs DSLRs
- Lack optical viewfinders
- Drop in brightness – Because part of the light is directed away from the image sensor, there is a drop in brightness (corresponding to about 1/3 of a stop). This may result in slower shutter speeds and may lead to some blur.
- Slower refresh rates – Electronic viewfinders have low refresh rates, especially in low light. This may result in a jerky image when you are moving the camera in low light while looking through the viewfinder. This low refresh rate is an important consideration if you do a lot of low light photography.
- Shows last image taken using burst mode – when using burst mode (keeping the shutter button pressed down to record a series on images) the electronic viewfinder will show the last image taken but not the actual scene in front of the camera. This maybe a concern if you intend to do a lot of fast action shots.
Which type of camera is right for me?
DSLRs are well-established in the market while SLTs are still relatively new to it. There is no doubt that with improvements in sensor technology and electronic viewfinders, SLTs best days are still ahead. What camera is right for you depends on a plethora of factors. Both systems have their own strengths and weaknesses and the best way to find out which is best for you is to actually get your hands on both systems and test them out for yourself.