Sigma 30 F1.4 Art lens in A900

A little help please
I've already bought a Sigma 30 Art
The problem is the my body A900 recognize this is a DT lens so the camera auto crop image
I've tried to push the lens release button the shoot, the result image is very little vignetting

Fullsize pic


Body auto cropped pic

Is there anybody can made the camera don't crop image for these DT lens?

pegelli wrote: Unfortunately there is no way to uncrop images from cropped lenses on the A850/A900 except by the "lens release button trick" you used, however then you lose the aperture control and AF. First camera on which this became an option is the A99

You mean the A99 can solve this problem? (Because of my English is not good so I ask again)

Hmmm, my A900 does not recognise my Tamron 18-200 as an DT lens, unlike my Sony lenses. I always thought the A900 automatically crops Sony lenses but not third party lenses. It seems Sigma got the protocol for DT lenses.

Some Sony lenses have identical LensID's to Minolta lenses, but the Sony's offer On Sensor AF with the Sony lenses but not with Minolta lenses. So, there is more information exchanged between lens and camera then just the ID.

But even then, it means Sigma (and Tamron) found a way to communicate these unique ID's and also communicate information on the format.

I just didn't know.

XKAES wrote: Just go to the SETUP MENU #4 -- it has an APS-C option -- ON or OFF. The default is ON, so with a DT lens, it crops. Just set it to OFF, and it won't crop!

Are you sure? My Sony 18-135 keeps cropping in both on and off positions.

Anyway, a belated welcome to Dyxum

XKAES wrote: Look at page 132 of your manual. If set to ON, it automatically crops a DT lens image to APS-C. If set to OFF, it doesn't. I'm using Version 2.0 of the A900/A850 firmware. Perhaps earlier versions are different, but I doubt it. Or perhaps there is something about your lens that is over-riding the camera's software -- somehow.

What APS-C lenses are you using on your a900 that still captures the full frame ?
Sony or third party ? The OP's lens is behaving normally .

I have an a900 running on version 2.0 firmware .
That's certainly not how that function works with all lenses .
On the menu in the tool section #4 it says "APS-C size capt(ure). ON or OFF .

With a full frame lens you can have set to "OFF" so you capture the full frame image with 24mp .
Set to "ON" and your getting the cropped image with just 11mp ( or thereabouts ) .

When you mount a Sony or Minolta DT ( APS-C) lens on it , regardless of if it's set to ON or OFF in the menu , the camera reverts to crop mode only , with no way to override it .
Apart from the image captured being a smaller field of view than what you see in the viewfinder , it is indicated on the LCD between the section that says what format the images are being saved as , cRAW , RAW etc , and where it indicates what memory card your using , CF or MS .
It is indicated as a picture of a box ( the frame ) with a dotted box around it to indicate the crop .

With third party lenses that identify themselves to the camera as a DT lens , it should revert to crop mode only .

Some third party lenses , especially early ones , might not identify themselves as a DT lens as they've been backward engineered and don't identify themselves correctly to the camera . With them it's up to you to set it in the menu what size frame you want to capture .

Just tried it with several Sony DT lenses and a Tamron 11-18mm , all the same , automatically going to APS-C mode with no way to override it .
Other than depressing the lens release button .

Page 132 in the manual just tells you how to change the camera from the default "OFF" setting to "ON" with full frame lenses to capture in crop mode .
Curiously I can't find mention in the manual that the camera defaults to crop mode with DT lenses , just a mention that APS-C lenses can cause vignetting and incorrect exposure .
Someone else can read the full 174 pages if they must , just to be sure !

Edited by neilt3 - 07 November 2021 at 23:11

Page 107: When attaching a DT lens, [APS-C size capt.] is automatically selected.
Page 157:
Using a DT lens is not guaranteed
because the corners of the field are
darkened and the camera does not
meet the primary AE performance
standard. [APS-C size capt.] is
automatically selected.