How To Get A 1.5x Magnification Boost With Your A850/A900

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How To Get A 1.5x Magnification Boost With Your A850/A900

Unread post by Pirate »



Well, as I'm sure all of you A850/A900 owners know, there's an A700 inside your FF body AND contrary to reports I've read, I can use all DC Sigma lenses on my A850 as well as others such as Tamron 17-50 F/2.8.

Now as you'll know, setting the format to APS-C means you can take images of 11MP using the viewfinders inner rectangle for the cropped lens in use, thus (when a WA lens is being used) the vignette you see in the viewfinder does not appear on the final image as it's in the area between the APS-C rectangle and the edge of the viewfinder used for FF lenses as shown below for the standard G focus screen:



Image Image
Image Image

So, how do you get your FF lenses to get this 1.5x boost? Simple . . turn on the APS-C option for cropped lenses when using a FF lens. Take a test shot in normal and APS-C modes, and you'll see the 1.5x crop factor applied to the image (albeit @ 11MP) but I'm sure it's the cheapest teleconverter you'll ever have that allows the lens to perform at it's maximum speed and without any loss of IQ.

How good is that? I have to 'assume' that this is something that has been known about since the introduction of the A850/A900, but having played around with the settings, it was an unexpected 'discovery'. What your images will look like if you already have a 1.4x or 2x TC already fitted I can only imagine.

Anyway, my coat is on the hook, so I'll be off now.
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Re: How To Get A 1.5x Magnification Boost With Your A850/A90

Unread post by Dusty »

The a350 has a button to do this on APS-C, but only when shooting JGP. I've found it much smarter to shoot the whole frame in RAW and just crop. You get the same effect, but can crop where you want to, not just the center.

An a700 and couple of a580s, plus even more lenses.
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Re: How To Get A 1.5x Magnification Boost With Your A850/A90

Unread post by David Kilpatrick »

It offers you no benefit over just shooting the whole raw frame or JPEG and cropping later - which also gives you extra leeway for framing moving subjects, try to keep them in the central 1.5X zone, but if you get a slight miss, it won't matter much.

What is more useful is the non-activation of the auto crop mode when you fit an alien lens.

Take a look at this tech article on Sigma wide-angles, which do not auto crop: ... us-8-16mm/

You will see that the 8-16mm can be used on the A900 - and presumably on the A99 - and gain the benefit of its full image area. This applies to many other lenses, such as the 10-20mm models.

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