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Sony?s Translucent Mirror May Reduce Detail in Photos by up to 5%


kombizz 14 601 1 United States
30 Aug 2011 5:43AM
Apparently one of the main downsides to having a translucent mirror is that the light hitting the sensor passes through an additional layer (the translucent mirror), which reduces the amount of light and the image quality.
Ray Lemieux attempted to quantify how much the mirror affects the resulting image quality by removing the mirror on his A55 and comparing the results. He confirmed that about 1/2 stop of light is lost, and estimates that 5% of the detail in each shot is lost due to the mirror.
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knikki91 13 35 United Kingdom
30 Aug 2011 11:20AM
I have seen a few threads knocking about questioning the light loss and image quality of the Sony cameras and I am not whole convinced.

Yes there will be some light loss as some of the light is bounced back up into the prism(?) but 1/2 stop lost?

I still use a Pellicle mirror film camera and there is about 1/4 light loss but there is no noticable loss of quality when you dev and scan/print the film.
macroman 16 15.3k England
30 Aug 2011 1:05PM
Here we go talking in percentages again! Grin

Would Sony concievably offer a new hi range expensive camera that loses 5% of the detail produced by the lens.?
Plus a 1/2 stop light loss?

Canon publicity dept at work?? Sad
strawman 15 22.1k 16 United Kingdom
30 Aug 2011 4:35PM

Quote:Would Sony concievably offer a new hi range expensive camera that loses 5% of the detail produced by the lens.?
Plus a 1/2 stop light loss?

err yes it has to loose some light from the sensor in order for the AF points to work but I thought it was more about 30% it is part of the pitch and toss of the design and the compromise you take. You get full time EVF with phase detection AF so something had to give. Detail 5% that sounds high, every element in the light path will alter image quality but I would be surprised if it was 5%.

Still it indicates that if you want to have full time EVF etc the mirror brings fast AF at a price. It is a compromise like everything but it is Sony's choice to have a different product.

Canon publicity dept at work?? Sad
Nah Sony users do enough themselves Tongue

Had a look at DPREVIEW they are even worse than Canon users 5 years back and many are laying into the A77 without trying.
JackAllTog Plus
10 5.6k 58 United Kingdom
30 Aug 2011 4:44PM
Light is lost - true; - but detail - I'm NOT AT ALL Convinced this is true, or even that one guy removing his own mirror is a valid test.
mdpontin 15 6.0k Scotland
30 Aug 2011 4:54PM
Take a look at Luminous Landscape's preview here .

Quoting from the piece:

Quote:No one at Sony would comment officially on the percentage of light loss, but I'd guess it to be about a third of a stop.


Also:

Quote:Pellicle mirror technology isn't new. Canon used it first in 1965 in the Canon Pellix and both Canon and Nikon had models with Pellicle mirrors during the 1970s.

(and in case you're wondering, what Sony describes as their 'Translucent Mirror System' is a pellicle mirror.)
mikehit 10 8.0k 13 United Kingdom
30 Aug 2011 5:03PM
How do evaluate 'detail', especially as small as a '5% loss' ? I am not convinced that file size is a direct correlation to detail. For example, if it is a sigmoid curve (perceived 'detail' against number of bits) then 5% loss at the top end will be almost unnoticable.

Someone is playing with meaningless numbers again because it sounds scientific.
macroman 16 15.3k England
30 Aug 2011 5:04PM
Strawman, I follow you argument, but the figures just struck me as being high.
At the end of the day though, it's the final image that matters, not all the mathematics.
strawman 15 22.1k 16 United Kingdom
30 Aug 2011 6:43PM
Macroman I agree with you there, the camera you use should give you the final image you want with the controls that allow you to capture the image when/how you want. And its nice to have choice. I would be interested to see how the new Sony sensor works. In the real world how much detail can you capture from an APS sensor (is it only an advantage if you have the best lenses) do more pixels make lens correction and noise reduction strategies work better or does it just bring more high ISO noise. I wonder if more pixels means you can make lower cost lenses work even better?
macroman 16 15.3k England
30 Aug 2011 7:00PM
There is only a limited amount of detail that any sensor can capture, and once your lens' resolution reaches/nears that limit you are just wasting your money.
strawman 15 22.1k 16 United Kingdom
30 Aug 2011 7:23PM
One of the things I noticed as I moved from "entry" lenses to more expensive ones was that contrast was more constant and distortion less with the more expensive lenses. But I also note that the RAW converter I have does a very good job of correcting distortion and dark corners on my compact camera. So I wonder if having a lot of data points means you can make a better 12mp output image. Just keen to see.
macroman 16 15.3k England
30 Aug 2011 7:45PM

Quote:as I moved from "entry" lenses to more expensive ones was that contrast was more constant and distortion less with the more expensive lenses


Wasn't that always the case, even in the dim and distant glorious days of film? Grin

Even with my old enlarger, my cheapo Japanese lens was never as contrasty as my Wray lens and that wasn't that expensive either.
The difference was quite noticeable but could be corrected with Multigrade filters.
1 Sep 2011 10:21PM
I hope to get some kingfisher pictures with the A77 tomorrow.
Then I will compare with my A850.
The proof of the pudding is in the picture.
strawman 15 22.1k 16 United Kingdom
1 Sep 2011 11:27PM
How did you get your hands on one Sydney as I thought it would not be production spec till October and what RAW converter do you have?
samfurlong 13 2.5k United Kingdom
2 Sep 2011 8:13AM

Quote:Apparently one of the main downsides to having a translucent mirror is that the light hitting the sensor passes through an additional layer (the translucent mirror), which reduces the amount of light and the image quality.
Ray Lemieux attempted to quantify how much the mirror affects the resulting image quality by removing the mirror on his A55 and comparing the results. He confirmed that about 1/2 stop of light is lost, and estimates that 5% of the detail in each shot is lost due to the mirror.



This is not new... anyone remember the early high speed canon EOS cameras - the EOS RT and the EOS 1NRs?? They had non moving , semi translucent mirrors and they were 20 years ago plus. Brilliant high speed cameras (10fps was amazing for the time). They suffered the same problems and as soon as technology improved to allow 6 - 8 fps with regular movable mirrors, Canon abandoned the fixed mirror.

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