Here we will discuss the Why Sony Mirrorless is Better than Sony SLT Technology. I will keep this article short to tell you the downside of the SLT technology used by Sony in its SLT series camera.
Now before we begin take a look at the image sensor below.
42.4-megapixel Exmor R CMOS sensor from Sony
The sensor you see above is the same sensor used inside the Sony A99 II and Sony A7R II camera. The sensor features 42 Megapixels of resolution and 399-point focal-plane AF system located on the image sensor.
Difference between SLT and Mirrorless
As you can see in the image the SLT technology uses a fixed translucent mirror inside that redirects some portion of light to the dedicated Phase AF sensor of the camera. Whereas the Mirrorless technology delivers 100% light to the sensor.
Which one is better: SLT or Mirrorless ?
Before speculating the percentage of light used by the mirror let’s see the sensor test score of both the camera carrying same sensor. The test Conducted by DXOMark Lab.
Sony A7R II outperformed Sony A99 II During Test
As you can see the low light ISO score of Sony A99 II camera is 2317 only whereas the low-light score of Sony A7R II camera is 3434. And not only low-light ISO the Dynamic range, Portrait and Overall score of the Sony A7R II camera is better than the Sony A99 II camera.
As you can see the result of same sensor inside two different camera body, which is completely different compared to each other. The fixed translucent mirror grabs out a good amount of light before reaching to the sensor and in-turn you get inferior image quality.
Sony A99 II is recommended when..
you want to shoot sports and birds on flight, the dedicated phase AF sensor works in-collaboration with 399-point on-chip focus system of Hybrid CMOS AF sensor.
| Features | Sony A99 II | Sony A7R II |
| 12 FPS with continuous AF | 5 FPS with continuous AF |
You can see the Sony A99 II offers continuous AF drive of 12fps with fulltime AF tracking whereas the Sony A7R II remains limited to 5fps of continuous shooting speed with AF tracking.
WOW
There is BIG difference in the performance of the same sensor. Thanks writing very informative article.
The downside is lens mount! Many of us have an array of A mount lenses and don’t want to use adapters. To replace the A mount lenses with E mount lenses becomes cost prohibitive. This is a big deal!
By this single measure mirrorless may win. But what is the real world significance? Will one be able to visually distinguish between photos of the same static scene taken by the two cameras given the relatively small difference in sensor scores? The answer is probably not. The most significant and real world difference between these two cameras is the speed and accuracy of autofocus. AF performance is dramatically better in the a99II than the a7rII. Because of limitations in mirrorless technology, no one has yet been able to produce a mirrorless camera that can come close to matching a mirrored camera (DSLR or SLT) in autofocus (AF) performance. Lets examine the real world impact of poor AF performance, as you have in the a7rII. If you shoot things that move, such as sports, children, animals, etc., particularly in low light conditions and/or distantly, a mirrorless camera is going to pump back and forth trying to acquire focus while the decisive moment passes by. A SLT, like the a99II, in the same conditions is going to be able to acquire focus instantaneously without “hunting” so you can capture the shot. Take it from someone who has shot with both cameras. The difference is huge.
As the article points out, FPS performance on the a99II is much better than the a7rII, but that is not the defining issue. Although the A7rII is relatively slow, that phenomenon is a function of the camera’s design and not an inherent shortcoming of today’s mirrorless technology. The crucial difference is the speed and accuracy of AF. By that crucial measure, today’s mirrorless technology is far behind. So what’s more important? A difference in image quality that you probably won’t be able to discern even by “pixel peeping,” or the inability to capture a photo you want to take in the field because a limitation of the technology? For me, the answer is clear. SLT technology is better than mirrorless.
Brian I agree. This is & irrelevant to real world results. Compare a downloaded A7rII 100 iso file with the 99II equivalent from Imaging resource of the set of bottles, crayons & fabric swatches & to my eye they are INDISTINGUISHABLE in terms of clarity & colour quality. The SLT mirror has zero quality loss issues to the eye at 100% scaling. If ‘Pro’s’ happily use the POORER sensor of the Canon 5DmkIII & IV to make high end PAID work, then so can users of the 99II.
As you correctly point out Brian, if capturing the descisive moment is what your work involves, then an A7rII is inferior.
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As an A7RII owner and user I’d have to disagree. I switched from Nikon expecting to be able to use the A7RII for professional work and it was not able to perform to my expectations.
I now have the A99II and I have finished photographing four winter weddings, where it performed flawlessly. The AF system is incredibly fast, accurate and reliable. There is zero lag between shots. The AF is superior to my D4, possibly the D5 and definately better than my D810 was.
The A99II was never designed to compete with the A7RII. It was designed for working professionals who need the absolute best in auto-focusing power achievable by the industry. This is where the A99II excels and making it Sony’s only professional ready camera.