A900 lens compatability with other Alpha DSLR's?

Gavin_P · Oct 30, 2008

I was toying with the idea of exchanging the body of my A350 for the A900 (just mulling it over mind you, not that I'm unhappy with what I have), and started reading through the specs of the A900 on the Sony UK website. Looks a very promising camera indeed, although I'm just hoping the price drops a bit over the next couple of years before I decide on anything!!

However, it says the following:

Lens Compatibility
All types of Sony α lenses
YES (DT lens compatibility is not guaranteed)
Minolta & Konica Minolta α MAXXUM/DYNAX lenses
YES (DT lens compatibility is not guaranteed)

Exactly what is a "DT lens"?

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Look out that window. Eden isn't burning, its burnt

headofdestiny · Oct 30, 2008

A DT lens is a lens designed for crop sensor cameras. They should be fine on the A900. The only issue comes with metering, and so matrix metering may have an issue in some cases, but no biggie.

Gavin_P · Oct 30, 2008

By chance while I was googling around to find a definition of a cropped sensor camera, I found an older thread on the Dpreview boards discussing the topic, however the APS-C sensor size was never specifically mentioned.

Is APS-C classed as being a cropped sensor? I guess anything smaller than full frame would be considered cropped now that the A900 has appeared and set a new standard...

--
Look out that window. Eden isn't burning, its burnt

headofdestiny · Oct 30, 2008

With Sony, Nikon, and Minolta DSLRs, crop sensor generally refers to APS-C. With Canon, it gets a little trickier, because they have 1.0x (fullframe,) 1.3x, and 1.6x.

The bottom line is that if you have DT lenses laying around, you can use them on the A900, but I wouldn't recommend buying them specifically for the A900. It's like putting plain old radials on a Ferrari.

Robert Lynch · Oct 30, 2008

Gavin_P said:
Is APS-C classed as being a cropped sensor? I guess anything smaller
than full frame would be considered cropped now that the A900 has
appeared and set a new standard...

The standard of "cropped" vs. "full frame" existed years before Sony entered the DSLR market. It is not new and dates to the very first DSLR that did not have a 35mm film frame sized sensor.

Gavin_P · Oct 30, 2008

The idea if I ever got an A900, it would be a body only, I would use all the lenses that I had for the A350. In the next couple of years, getting suitable FF lenses for the A900 (and whatever other FF models Sony will have out by then) shouldn't be a problem.

Perhaps in the next couple of years, getting an A900 body may be an option worth looking at?

--
Look out that window. Eden isn't burning, its burnt

Klipsen · Oct 30, 2008

Gavin_P said:
Exactly what is a "DT lens"?

DT supposedly stands for Digital Technology, and owes its name to the belief that digital cameras would generally have APS-C sensors. There's also changes to coatiings, but that wouldn't prevent their use on full frame cameras.

From what I've read, the A900 automatically switches to "11 Mpix crop mode" when a DT lens is mounted.

Gavin_P · Oct 30, 2008

Klipsen said:
Gavin_P said:

Exactly what is a "DT lens"?

Click to expand...

DT supposedly stands for Digital Technology, and owes its name to the
belief that digital cameras would generally have APS-C sensors.
There's also changes to coatiings, but that wouldn't prevent their
use on full frame cameras.
From what I've read, the A900 automatically switches to "11 Mpix crop
mode" when a DT lens is mounted.

Interesting info, Klipsen. Thank you. Not that I'm doubting you of course, but are there any A900 users who can confirm this does indeed happen? I'm quite impressed to hear the camera would be able to change settings like that without operator intervention.

--
Look out that window. Eden isn't burning, its burnt

headofdestiny · Oct 30, 2008

Gavin_P said:
Klipsen said:

Gavin_P said:

Exactly what is a "DT lens"?

Click to expand...

DT supposedly stands for Digital Technology, and owes its name to the
belief that digital cameras would generally have APS-C sensors.
There's also changes to coatiings, but that wouldn't prevent their
use on full frame cameras.
From what I've read, the A900 automatically switches to "11 Mpix crop
mode" when a DT lens is mounted.

Click to expand...

Interesting info, Klipsen. Thank you. Not that I'm doubting you of
course, but are there any A900 users who can confirm this does indeed
happen? I'm quite impressed to hear the camera would be able to
change settings like that without operator intervention.

--
Look out that window. Eden isn't burning, its burnt

--

This is true. The camera automatically switches to APS-C crop mode with Sony or Minolta DT lenses. It doesn't do so with Sigma, Tamron, etc crop lenses.

FWIW, you may be better off spending $3000 on the best glass before you buy the A900. Better glass will probably make a bigger difference for you. What lenses do you have now?

Gavin_P · Oct 30, 2008

headofdestiny said:
This is true. The camera automatically switches to APS-C crop mode
with Sony or Minolta DT lenses. It doesn't do so with Sigma, Tamron,
etc crop lenses.

FWIW, you may be better off spending $3000 on the best glass before
you buy the A900. Better glass will probably make a bigger
difference for you. What lenses do you have now?

At present I have a SAL-75300 300mm zoom, a SAL 500F80 500mm mirror lens and a SAL-20F28 28mm super wide angle lens. I am expecting the Sigma 50-500mm lens to arrive at any time now (with a Manfrotto monopod).

Can this "downgrade" to crop mode be manually controlled on the A900?

Thanks

--
Look out that window. Eden isn't burning, its burnt

headofdestiny · Oct 30, 2008

--

Well, you've got a lot covered on the long-end especially, so I'm guessing you could go with the opposite. For ~$3000, you could buy a Zeiss 24-70 and a Zeiss 85mm which would be incredible on that 14MP sensor. The cool thing about dropping money into lenses is that, not only does it give you a boost in IQ, but lenses also hold they're value very well, whereas camera bodies become worth next to nothing in a few years. I tend to lean more towards spending money on lenses before camera bodies, but that's just me.

Unfortunately, I don't believe you can override the crop mode with DT lenses on the A900.

Chefir · Oct 30, 2008

Actually, I've read that you can do it. But I don't own an a900, so I don't know the specifics. You can do something in the menus, don't know what exactly.
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Cheers,
Jacek

Gavin_P · Oct 30, 2008

headofdestiny said:
Unfortunately, I don't believe you can override the crop mode with DT
lenses on the A900.

I was wondering about me now (almost) having the Sigma 50-500mm lens, the fact that the A900 won't recognise it enough to downgrade to the crop sensor size. If the downgrade function does have a manual control, then the lens will work fine. I'm rather dubious about getting the A900 body if I couldn't use this lens on it to the best of its capability. As for my choices of lens, most of the time I am some distance away from my specific picture in mind. Its not all that often that I use the wide angle lens but it is handy to have.

I wouldn't be getting rid of the A350 body anyway, as long as its still operational then it would still be used.

Re Jefir's post; I haven't found a full pdf manual yet for the A900 but your comment on the menu's is very interesting. I will have to keep looking!
--
Look out that window. Eden isn't burning, its burnt

Leon van Bommel · Oct 30, 2008

Gavin_P said:
I was wondering about me now (almost) having the Sigma 50-500mm lens,
the fact that the A900 won't recognise it enough to downgrade to the
crop sensor size.

Why worry? It's FF anyway. It's a DG, not a DC lens. Which means it has the coating on the rear element, but it's not a cropped design (with Sigma DC = DT).

Leon van Bommel · Oct 30, 2008

You do know all those lenses you mentioned are already FF? So there's little to nothing holding you back when you want to move to a FF body like the A900 (or it's successor)?

Gavin_P · Oct 30, 2008

Now I begin showing how little I know lol.

Problem solved then, could get myself an A900 in a year or two perhaps. £2000 is a bit on the steep side for a camera body only, so waiting a while is perhaps the best idea!

Thanks everyone for all your help.

--
Look out that window. Eden isn't burning, its burnt

headofdestiny · Oct 30, 2008

Yes, you have fullframe glass, but it still doesn't go against my point that you could have better fullframe glass. $3000 is a lot to spend on a body, and you have to decide if you'd rather put average glass on a great body, or great glass on an average body. I tend to think the latter makes more sense, unless you're making gigantic prints. For $3000, you could buy the upcoming 70-400 G lens and a few more primes for the wider end.

sinusundo · Oct 30, 2008

Yes, the A900 will automatically drop from 24.6 to 11 megapixels (or a likewise amount at lower resolutions) if you attach a DT lens. Note this will only occur when taking photos in 3:2. Widescreen (16:9) images are not possible with a DT lens, so in this case the A900 will drop you back to 3:2 and then the drop to 11 megapixels.

This is mentioned in the user's guide, but I also experienced this firsthand.

sinusundo · Oct 30, 2008

Gavin_P said:
At present I have a SAL-75300 300mm zoom, a SAL 500F80 500mm mirror
lens and a SAL-20F28 28mm super wide angle lens.

Can this "downgrade" to crop mode be manually controlled on the A900?

You cannot disable the automatic downgrade to APS-C when using a DT lens.

However, none of your current lenses you listed are DT lenses. Most of the Alpha zoom lenses are DT, but the SAL-75300 is not... though the optics in this particular lens may not result in ideal images at 24.6 megapixels.

Incidentally, you CAN control whether or not you drop to APS-C sensor resolution when using a non-DT lens. Most will not want to do this, but some may wish to do so to create a sort of "smart" 1.5x teleconverter effect.

Robert Lynch · Oct 30, 2008

sinusundo said:
Incidentally, you CAN control whether or not you drop to APS-C sensor
resolution when using a non-DT lens. Most will not want to do this,
but some may wish to do so to create a sort of "smart" 1.5x
teleconverter effect.

Or when using a non-Sony/Minolta lens that the camera does not automatically recognize as having a smaller image circle.

A900 lens compatability with other Alpha DSLR's?

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