Full-frame shots with DT lenses

[01af]

Did you know it's possible to take full-frame shots with DT lenses on the A900? Just press the lens release button prior to firing the shutter!

Normally, the A900 camera will switch to APS-C shooting mode automatically as soon as a DT lens (i. e. a lens with a reduced image circle designed for the digital APS-C format) is mounted. An exception to this rule is the Tamron SP AF 11-18 mm 1:4.5-5.6 Di-II which for some reason the camera doesn't recognise as an APS-C-format lens, and maybe a few more 3rd-party APS-C lenses ... but Minolta AF-DT lenses and Sony SAL DT lenses cannot be used in full-frame shooting mode.

Except when you're using 'M' exposure mode and press the the lens release button just before firing the shutter. Don't forget to enable shutter actuation with 'no lens attached' in the set-up menu. Then the A900 happily will happily fire the shutter and record a 24 MP full-frame image with pitch-dark corners with any DT lens. The downside is, you'll lose the recording of the aperture and the focal length settings in the EXIF data.

No, I didn't find out myself; Jakub Kubica disclosed this trick in the Sony SLR Talk forum on dpreview.com.

I suppose the A850 will behave the same way. Can anyone confirm?

-- Olaf

[David Kilpatrick]

I'll have to check to see what happens with the aperture. The only lens it's really useful on is the KM/Sony 11-18mm, which unlike the Tamton defaults to crop. Nearly every other crop format lens I have used produces a vignetted circle, not a full frame, including the Sigma 10-20mm old and new types which can't be used the same way. I think the 18-55mm or 18-70mm kit lenses may be able to cover full frame at 1.5X their minimum focal length - i.e. 27mm or so. I no longer have one to check.

David

[pakodominguez]

Interesting...
The lens Jakub tried, the 30mm macro, is a nice one, and I wish it will work FF. I'll go tomorrow at lunch time to the store and try a couple of lenses.

Regards

[01af]

I'll have to check to see what happens with the aperture.

Oh yes, the aperture. Doh. Why didn't I think of that ...?

Yesterday evening I tried the trick with the Konica-Minolta AF-DT 11-18 mm in the dark---at full aperture of course, which works just fine. But it's not possible to stop down. With the lens release button pressed down, the camera won't close the diaphragm down to working aperture at exposure time.

So this trick will work at the lens' full aperture only.

You can "stop down" the lens if you not only press the lens release button but also turn the lens half-way out of the bayonet mount. But this way you'll never know the exact aperture setting---you can only estimate by looking into the front element and watching the aperture blades closing down while you're rotating the lens in the mount---and it's dangerous because the lens may eventually fall off the body as it won't be safely attached to the body anymore.

-- Olaf

[pakodominguez]

I'll have to check to see what happens with the aperture.

Oh yes, the aperture. Doh. Why didn't I think of that ...?

So, I went to the store in order to try a DT lens on the A850 and no, the aperture doesn't work.
In other hand, I don't know if I want a DT lens anyways...

Regards

[TomB]

Interesting trick! I always wonder why the DT lenses are artificially limited to APS-C picture size. One could take nice square pictures on full-frame cameras and get more vertical resolution from them. It should be my decision how the picture will look like, not a decision of the camera. The photographer should have the possibility to switch off all fool-proof features. One can make a bad exposure in M mode and nobody will blame the camera... (I know, manufacturers need to sell FF lenses.)

[alphaPDX]

I keep watching for some forum member, somewhere, to report on the 17-70 Sigma on FF. If it works decently, it would be a cheap 28-70 f/3.5-4.5 alternative yet still useful below 28mm. Maybe it would fail the 24mpxl test.. but nobody has said anything to my knowledge.

Anyone want to loan me a FF for a "week" or so?