Why did Sony bother with SLT?

Started Dec 11, 2013 | Discussions
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Pete peterson
Pete peterson Regular Member • Posts: 372
Why did Sony bother with SLT?

This question hadn't occurred to me until the Alpha 3000.

Why did Sony bother with a stop-losing translucent mirror on cameras with built-in EVF? They could have kept the DSLR shape and all the external controls and just lost the mirror.

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007peter
007peter Forum Pro • Posts: 10,477
buying time for On-Sensor-PDAF technology to catch up
9

CDAF is very slow 4-5 years ago, and there is no way for Sony Alpha to achieve any reasonable focusing speed without using a traditional mirror (SLR) or a translucent mirror (SLT).

PDAF-on-sensor was an exotic technology then; it take time for manufacture to work out the kinks & bugs before massive production.

Now the on-sensor-PDAF is ready, just about every manufacture (canon, sony, fuji....) has one.  Those without are being left behind.  Fuji has a lot of patent on OSPDAF, that is why Panasonic decides to team up with Fuji, where as Olympus can buy OSPDAF from Sony in the future.

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Aberaeron Senior Member • Posts: 4,979
Re: Why did Sony bother with SLT?
1

Pete peterson wrote:

This question hadn't occurred to me until the Alpha 3000.

Why did Sony bother with a stop-losing translucent mirror on cameras with built-in EVF? They could have kept the DSLR shape and all the external controls and just lost the mirror.

Because they rightly deduced that there are a whole lot of potential customers out there that believe a mirror makes their camera a cut above others. They think the size and heft of that form factor is important.

Besides which the mirror design did make a practical difference to focus speed and focus-tracking at that time due to the limitations of on-sensor focussing.

Today, of course, mirrorless has nearly caught up with improved sensor focussing, which should manifest itself even more demonstrably on the next generation of mirrorless cameras and sensors.

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Thorgrem Regular Member • Posts: 474
Re: Why did Sony bother with SLT?
1

Aberaeron wrote:

Pete peterson wrote:

This question hadn't occurred to me until the Alpha 3000.

Why did Sony bother with a stop-losing translucent mirror on cameras with built-in EVF? They could have kept the DSLR shape and all the external controls and just lost the mirror.

Because they rightly deduced that there are a whole lot of potential customers out there that believe a mirror makes their camera a cut above others. They think the size and heft of that form factor is important.

What marketshare had Sony with the dSLR's? And did the marketshare changed with the SLT?

It seems to me that, in spite of Sony put a lot of money into great camera's it didn't matter and Sony couldn't penetrate the Canikon marketshare.

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Aberaeron Senior Member • Posts: 4,979
Re: Why did Sony bother with SLT?
1

Thorgrem wrote:

Aberaeron wrote:

Pete peterson wrote:

This question hadn't occurred to me until the Alpha 3000.

Why did Sony bother with a stop-losing translucent mirror on cameras with built-in EVF? They could have kept the DSLR shape and all the external controls and just lost the mirror.

Because they rightly deduced that there are a whole lot of potential customers out there that believe a mirror makes their camera a cut above others. They think the size and heft of that form factor is important.

What marketshare had Sony with the dSLR's? And did the marketshare changed with the SLT?

It seems to me that, in spite of Sony put a lot of money into great camera's it didn't matter and Sony couldn't penetrate the Canikon marketshare.

That is another issue altogether, but I am under the immersion that their SLT sales have done far better than pre-SLT models. They certainly deserve to do very well. With on-sensor phase detection focus being quickly perfected just now, the days of the SLT could be numbered. Not that it matters one way or another. What the camera does and the user experience is far more important than the internal architecture and engineering. The SLT still scores highly in my book. The translucent mirror is not a novel feature anyway, with many ordinary DSLR's also having such mirrors to enable the light to pass through the upward main mirror to a secondary mirror behind that deflects part of the light downwards to the focus sensor. Yet people still claim that the optical viewfinders fitted to these cameras are bright, or they have not noticed any loss of light at any rate.

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OpticsEngineer Senior Member • Posts: 4,817
Re: Why did Sony bother with SLT?
5

For your answer, look at the alternative.  For instance, here on dpreview in the reviews for cameras like Nikon DSLRs D7100, D5300, read the Cons in the conclusion section.   Slow AF in LiveView is always mentioned.   Sony has the same LiveView type functionality but with very fast AF.   And it works in video mode too.

I have a D7100 and like dpreview comments, AF in LiveView is quite slow.   Not nearly as good as my Sony A65 for taking pictures of my children's activities.

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joejack951 Senior Member • Posts: 2,682
Re: Why did Sony bother with SLT?

Aberaeron wrote:

The translucent mirror is not a novel feature anyway, with many ordinary DSLR's also having such mirrors to enable the light to pass through the upward main mirror to a secondary mirror behind that deflects part of the light downwards to the focus sensor. Yet people still claim that the optical viewfinders fitted to these cameras are bright, or they have not noticed any loss of light at any rate.

Are the optical viewfinders in pentaprism cameras not bright to you? Yes, they could be brighter (very slightly, like a manual film camera viewfinder) but they still work very nicely for me.

And when a picture is taken, there is no loss of light at the sensor in a DSLR like there is with a Sony DSLT. The mirror is completely out of the loop when the sensor is exposed unlike the fixed DSLT mirror. That's the big downside of the latter (respecting the fact that OVFs and EVFs have their own pluses and minuses).

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Sonyshine
Sonyshine Senior Member • Posts: 8,068
Re: Why did Sony bother with SLT?
4

Speed.

fast frames per second

fast live view

fast video

fast focusing

Less vibration-no clunking mirror

WYSIWYG brilliant viewfinder and LCD

I guess it's only a matter of time before mirrorless cameras catch up.

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tjwaggoner
tjwaggoner Senior Member • Posts: 1,112
Re: Why did Sony bother with SLT?
4

Pete peterson wrote:

This question hadn't occurred to me until the Alpha 3000.

Why did Sony bother with a stop-losing translucent mirror on cameras with built-in EVF? They could have kept the DSLR shape and all the external controls and just lost the mirror.

Fast focusing during live view and video recording.

And it isn't a loss of a stop. Many people have taken the mirror out and took pictures to compare and found very little to no real world difference.

-- hide signature --

Constructive Criticism is always welcome, however please understand that I am not a pixel peeper.

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Aberaeron Senior Member • Posts: 4,979
Re: Why did Sony bother with SLT?
1

joejack951 wrote:

Aberaeron wrote:

The translucent mirror is not a novel feature anyway, with many ordinary DSLR's also having such mirrors to enable the light to pass through the upward main mirror to a secondary mirror behind that deflects part of the light downwards to the focus sensor. Yet people still claim that the optical viewfinders fitted to these cameras are bright, or they have not noticed any loss of light at any rate.

Are the optical viewfinders in pentaprism cameras not bright to you? Yes, they could be brighter (very slightly, like a manual film camera viewfinder) but they still work very nicely for me.

And when a picture is taken, there is no loss of light at the sensor in a DSLR like there is with a Sony DSLT. The mirror is completely out of the loop when the sensor is exposed unlike the fixed DSLT mirror. That's the big downside of the latter (respecting the fact that OVFs and EVFs have their own pluses and minuses).

The SLT cameras work perfectly well and like your optical viewfinder. Any slight difference is amplified by the competition who, understandably, are keen to exploit any potential vulnerability in a serious rival that has a system that provides many features than they cannot.

I should explain that I have had several conventional DSLR's over the years, still have one while also having an SLT and several mirrorless, and I am not brand loyal and don't have any affiliation to any brand or system in any way.

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joejack951 Senior Member • Posts: 2,682
Re: Why did Sony bother with SLT?

Aberaeron wrote:

joejack951 wrote:

Aberaeron wrote:

The translucent mirror is not a novel feature anyway, with many ordinary DSLR's also having such mirrors to enable the light to pass through the upward main mirror to a secondary mirror behind that deflects part of the light downwards to the focus sensor. Yet people still claim that the optical viewfinders fitted to these cameras are bright, or they have not noticed any loss of light at any rate.

Are the optical viewfinders in pentaprism cameras not bright to you? Yes, they could be brighter (very slightly, like a manual film camera viewfinder) but they still work very nicely for me.

And when a picture is taken, there is no loss of light at the sensor in a DSLR like there is with a Sony DSLT. The mirror is completely out of the loop when the sensor is exposed unlike the fixed DSLT mirror. That's the big downside of the latter (respecting the fact that OVFs and EVFs have their own pluses and minuses).

The SLT cameras work perfectly well and like your optical viewfinder. Any slight difference is amplified by the competition who, understandably, are keen to exploit any potential vulnerability in a serious rival that has a system that provides many features than they cannot.

You implied that DSLR's suffer light loss like DSLT's. I was only attempting to clarify that statement. Whether or not someone can perceive the light loss at the sensor on a DSLT vs. DSLR, it's there. It has to be because that's how physics works. For a lot of people, that's a big thing.

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Jack Hass Regular Member • Posts: 392
Re: Why did Sony bother with SLT?
1

joejack951 wrote:

Aberaeron wrote:

joejack951 wrote:

Aberaeron wrote:

The translucent mirror is not a novel feature anyway, with many ordinary DSLR's also having such mirrors to enable the light to pass through the upward main mirror to a secondary mirror behind that deflects part of the light downwards to the focus sensor. Yet people still claim that the optical viewfinders fitted to these cameras are bright, or they have not noticed any loss of light at any rate.

Are the optical viewfinders in pentaprism cameras not bright to you? Yes, they could be brighter (very slightly, like a manual film camera viewfinder) but they still work very nicely for me.

And when a picture is taken, there is no loss of light at the sensor in a DSLR like there is with a Sony DSLT. The mirror is completely out of the loop when the sensor is exposed unlike the fixed DSLT mirror. That's the big downside of the latter (respecting the fact that OVFs and EVFs have their own pluses and minuses).

The SLT cameras work perfectly well and like your optical viewfinder. Any slight difference is amplified by the competition who, understandably, are keen to exploit any potential vulnerability in a serious rival that has a system that provides many features than they cannot.

You implied that DSLR's suffer light loss like DSLT's. I was only attempting to clarify that statement. Whether or not someone can perceive the light loss at the sensor on a DSLT vs. DSLR, it's there. It has to be because that's how physics works. For a lot of people, that's a big thing.

Yea this light loss was the reason I shied away from the SLT offerings. I don't need anything making IQ worse, and if I needed PDAF I would just buy a DSLR. Even today, on sensor PDAF is pathetic, true DSLRs will remain the go to for serious photographers.

PerL Forum Pro • Posts: 13,465
This is the reason.
4

Pete peterson wrote:

This question hadn't occurred to me until the Alpha 3000.

Why did Sony bother with a stop-losing translucent mirror on cameras with built-in EVF? They could have kept the DSLR shape and all the external controls and just lost the mirror.

The superiority of PDAF (Sony A55 with 70-200 2.8 wide open).

I doubt that the on-sensor PDAF has reached this level.

Aberaeron Senior Member • Posts: 4,979
Re: Why did Sony bother with SLT?

joejack951 wrote:

Aberaeron wrote:

joejack951 wrote:

Aberaeron wrote:

The translucent mirror is not a novel feature anyway, with many ordinary DSLR's also having such mirrors to enable the light to pass through the upward main mirror to a secondary mirror behind that deflects part of the light downwards to the focus sensor. Yet people still claim that the optical viewfinders fitted to these cameras are bright, or they have not noticed any loss of light at any rate.

Are the optical viewfinders in pentaprism cameras not bright to you? Yes, they could be brighter (very slightly, like a manual film camera viewfinder) but they still work very nicely for me.

And when a picture is taken, there is no loss of light at the sensor in a DSLR like there is with a Sony DSLT. The mirror is completely out of the loop when the sensor is exposed unlike the fixed DSLT mirror. That's the big downside of the latter (respecting the fact that OVFs and EVFs have their own pluses and minuses).

The SLT cameras work perfectly well and like your optical viewfinder. Any slight difference is amplified by the competition who, understandably, are keen to exploit any potential vulnerability in a serious rival that has a system that provides many features than they cannot.

You implied that DSLR's suffer light loss like DSLT's. I was only attempting to clarify that statement. Whether or not someone can perceive the light loss at the sensor on a DSLT vs. DSLR, it's there. It has to be because that's how physics works. For a lot of people, that's a big thing.

But you conveniently ignore the same loss of light to the optical viewfinder. Whether or not it is perceptible, it's there. It has to be because that's how physics works. Nobody notices and nobody cares, that's the truth of it.

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joejack951 Senior Member • Posts: 2,682
Re: Why did Sony bother with SLT?

Aberaeron wrote:

joejack951 wrote:

Aberaeron wrote:

joejack951 wrote:

Aberaeron wrote:

The translucent mirror is not a novel feature anyway, with many ordinary DSLR's also having such mirrors to enable the light to pass through the upward main mirror to a secondary mirror behind that deflects part of the light downwards to the focus sensor. Yet people still claim that the optical viewfinders fitted to these cameras are bright, or they have not noticed any loss of light at any rate.

Are the optical viewfinders in pentaprism cameras not bright to you? Yes, they could be brighter (very slightly, like a manual film camera viewfinder) but they still work very nicely for me.

And when a picture is taken, there is no loss of light at the sensor in a DSLR like there is with a Sony DSLT. The mirror is completely out of the loop when the sensor is exposed unlike the fixed DSLT mirror. That's the big downside of the latter (respecting the fact that OVFs and EVFs have their own pluses and minuses).

The SLT cameras work perfectly well and like your optical viewfinder. Any slight difference is amplified by the competition who, understandably, are keen to exploit any potential vulnerability in a serious rival that has a system that provides many features than they cannot.

You implied that DSLR's suffer light loss like DSLT's. I was only attempting to clarify that statement. Whether or not someone can perceive the light loss at the sensor on a DSLT vs. DSLR, it's there. It has to be because that's how physics works. For a lot of people, that's a big thing.

But you conveniently ignore the same loss of light to the optical viewfinder. Whether or not it is perceptible, it's there. It has to be because that's how physics works. Nobody notices and nobody cares, that's the truth of it.

I didn't ignore anything. I acknowledged it but said that the viewfinder still works good enough. And very importantly, that slight light loss at the viewfinder has zero effect on the image quality of my camera. It does, however, offer the great benefit of PDAF and an optical viewfinder, which for many, offsets the negative of the slightly dimmer viewfinder. And while it may detract from the shooting experience for some, it detracts nothing from every image I capture, quite the opposite of Sony's translucent mirror arrangement, which does detract something (a significant chunk of light) from every image. There are benefits (same PDAF whether using viewfinder or rear screen plus PDAF for movies) but for some, it's impossible to ignore the negative impact on the final product.

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ZodiacPhoto
ZodiacPhoto Contributing Member • Posts: 739
Re: buying time for On-Sensor-PDAF technology to catch up
2

Don't forget the large group of photographers who had Minolta lenses - those lenses would not work with CDAF, and supports from Minolta users community made it possible for Sony to succeed with their SLTs.

007peter wrote:

Now the on-sensor-PDAF is ready, just about every manufacture (canon, sony, fuji....) has one. Those without are being left behind. Fuji has a lot of patent on OSPDAF, that is why Panasonic decides to team up with Fuji, where as Olympus can buy OSPDAF from Sony in the future.

Olympus already has (bought from Sony) OSPDAF in their E-M1.

RedFox88 Forum Pro • Posts: 25,257
Re: Why did Sony bother with SLT?
1

Aberaeron wrote:

Today, of course, mirrorless has nearly caught up with improved sensor focussing,\

Sorry but no, not even close.  All cameras focus well in good light, but when light level drop P&S cameras and mirrorless/EVIL cameras struggle and need a focus assist light where an SLR will put mirrorless cameras to bed.

dinoSnake Senior Member • Posts: 1,608
Re: Why did Sony bother with SLT?

Actually, and I *know* I am in the minority, I wish Sony had stuck with the SLT format but in the same physical size as the original 35/55 twins.

If anything, Sony messed up by enlarging the bodies of the SLT design - why lose 2/3 stop for SLT if you can get the better performance with no (size) penalty? Resizing the line to directly compete with dSLR seems to be the common failing of the "second-tier" manufacturers - Panasonic, Sony and (to a point) Olympus all made this same mistake. If you *can* offer a benefit in smaller size over dSLR then DO SO - to have the ability due to the inherent design of the optical path, and then not use it and go against dSLR sizing, is a death warrant. Why give up all of the inherent design benefits of (APS-C) dSLR if you gain few to no advantage?

Sometimes I REALLY wonder about the decision making abilities of management.

Aberaeron Senior Member • Posts: 4,979
Re: Why did Sony bother with SLT?

RedFox88 wrote:

Aberaeron wrote:

Today, of course, mirrorless has nearly caught up with improved sensor focussing,\

Sorry but no, not even close. All cameras focus well in good light, but when light level drop P&S cameras and mirrorless/EVIL cameras struggle and need a focus assist light where an SLR will put mirrorless cameras to bed.

You are basing that on older generation current models, not on the latest generation such as the recently introduced Panasonic where most of the reviews I've read see little if any difference between it and a good SLR. Without checking my facts, I think it focuses quickly and accurately to -3EV, but do check on that. I might be thinking of the new Sony? Anyhow, the point is that the difference in low light autofocus is small and getting smaller with each new generation and the myriad other advantages of a mirrorless design overwhelm most of the historic disadvantages that are being addressed by designers.

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Aberaeron Senior Member • Posts: 4,979
Re: Why did Sony bother with SLT?

Jack Hass wrote:

joejack951 wrote:

Aberaeron wrote:

joejack951 wrote:

Aberaeron wrote:

The translucent mirror is not a novel feature anyway, with many ordinary DSLR's also having such mirrors to enable the light to pass through the upward main mirror to a secondary mirror behind that deflects part of the light downwards to the focus sensor. Yet people still claim that the optical viewfinders fitted to these cameras are bright, or they have not noticed any loss of light at any rate.

Are the optical viewfinders in pentaprism cameras not bright to you? Yes, they could be brighter (very slightly, like a manual film camera viewfinder) but they still work very nicely for me.

And when a picture is taken, there is no loss of light at the sensor in a DSLR like there is with a Sony DSLT. The mirror is completely out of the loop when the sensor is exposed unlike the fixed DSLT mirror. That's the big downside of the latter (respecting the fact that OVFs and EVFs have their own pluses and minuses).

The SLT cameras work perfectly well and like your optical viewfinder. Any slight difference is amplified by the competition who, understandably, are keen to exploit any potential vulnerability in a serious rival that has a system that provides many features than they cannot.

You implied that DSLR's suffer light loss like DSLT's. I was only attempting to clarify that statement. Whether or not someone can perceive the light loss at the sensor on a DSLT vs. DSLR, it's there. It has to be because that's how physics works. For a lot of people, that's a big thing.

Yea this light loss was the reason I shied away from the SLT offerings. I don't need anything making IQ worse, and if I needed PDAF I would just buy a DSLR. Even today, on sensor PDAF is pathetic, true DSLRs will remain the go to for serious photographers.

You are welcome to keep on believing that while I enjoy using both types and an SLT.

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