My Sony SLT-A99 Full-Frame DSLR Article Is Live

[OldClicker]

It's pretty sure that the sensor is not exactly the same as the one in the Nikon D600. The pixel count and sensor area aren't the same, plus the D600 doesn't have on-sensor focus-detect areas.

You didn't mention in your review that Sony have abandoned the old Minolta flash shoe and gone back to the "standard" shoe used by the other manufacturers. I watched a couple of video clips by online video magazines and they seem to think it's pretty important.

My opinion: it seems to be heavily orientated towards video. But with the SLT system that means that only 30% of the light coming in the viewfinder is used for focussing and only 70% is used to take the picture and that's not what I want. I was in a dimly-lit studio today with a moving model and it was a struggle to get the autofocus to work.

It could be the same sensor since, I believe, the main sensor PDAF is on a separate layer. There was a lot of denial with the D800, but it's a Sony.

Except for the die hard Minoltians, we are happy to have a stardard flash mount. Won't need to worry about that adapter when I go to a studio shoot. I believe Sony's reason, though, was to get compatibility with their pro video accessories.

I don't get your light-focussing problem. What percent of the light do you think goes through the primary mirror for focussing an a traditional DSLR?

Terry

[Greg McCary]

It could be the same sensor since, I believe, the main sensor PDAF is on a separate layer. There was a lot of denial with the D800, but it's a Sony.

Except for the die hard Minoltians, we are happy to have a stardard flash mount. Won't need to worry about that adapter when I go to a studio shoot. I believe Sony's reason, though, was to get compatibility with their pro video accessories.

I don't get your light-focussing problem. What percent of the light do you think goes through the primary mirror for focussing an a traditional DSLR?

Terry

I guess I will need the adapter I am heavy into the Sony flashes and don't want to buy new ones. I hope the a99 has the DR of the D800.

[Franglais]

It could be the same sensor since, I believe, the main sensor PDAF is on a separate layer...

I don't get your light-focussing problem. What percent of the light do you think goes through the primary mirror for focussing an a traditional DSLR?

The D600 sensor has the same dimensions as the D3X sensor (which was made by Sony). The A99 sensor dimensions are slightly smaller. But it might just be that they don't use all of the available surface.

Now my understanding of focussing on a traditional DSLR is that 100% of the light arrives on the mirror and is used for viewing or focussing (OK tell me that's not the case and just part gets diverted to a focussing unit somewhere else). When the mirror flips up 100% of the light is used for exposure.

[OldClicker]

The D600 sensor has the same dimensions as the D3X sensor (which was made by Sony). The A99 sensor dimensions are slightly smaller. But it might just be that they don't use all of the available surface.

Now my understanding of focussing on a traditional DSLR is that 100% of the light arrives on the mirror and is used for viewing or focussing (OK tell me that's not the case and just part gets diverted to a focussing unit somewhere else). When the mirror flips up 100% of the light is used for exposure.

In a traditional DSLR there are small semi-transparent areas (slits or crosses, I believe - hence the line or cross focusing points) on the main mirror and a small mirror behind it that transmits some of the light to the PDAF sensor on the bottom of the camera. Here is a diagram.

Sensorcleaning.com Main Page

Terry

[Franglais]

In a traditional DSLR there are small semi-transparent areas (slits or crosses, I believe - hence the line or cross focusing points) on the main mirror and a small mirror behind it that transmits some of the light to the PDAF sensor on the bottom of the camera. Here is a diagram.

Sensorcleaning.com Main Page

Terry

OK I see about the slits. But as I said - 100% of the light coming through the lens that happens to go through the slit is going to be available to the autofocus sensor. Whereas with the SLT system only about 30% of the light coming through the lens is going to the 19 autofocus sensors. The other 70% is going to the imaging sensor - where it can be used by the on-sensor autofocus sensors.

I checked out the specifications for the latest cameras and the low light limit for their autofocus systems:

Sony A99, Nikon D600, Nikon D7000 = -1EV
Nikon D800, Canon 1DX = -2EV
Canon 6D = -3EV (wow!)

So it doesn't look like this is a problem. I think that previous-generation (Nikon D3..) all stopped at -1EV as well.