A new research note from KGI indicates that the 4.7-inch model of the iPhone 6 won’t support optical image stabilization due to constraints in the production of VCM suppliers. The larger 5.5-inch version is expected to support the feature, while the smaller device will employ a cheaper motor that’s similar to the one found in the iPhone 5s.

Rather, we predict it will use a middle-mount type of open-loop VCM updated from the one used in the existing iPhone 5S. The 5.5” iPhone 6 is more likely to be equipped with OIS VCM due to lower estimated shipments and the need for more product features to differentiate itself from the 4.7” iPhone 6.

The difference will reportedly be one of the factors that sets the two devices apart, lending further credence to the idea that these will not simply be two internally-identical devices with different display sizes as is currently the case with the iPad its “mini” counterpart.

That’s not to say that the 4.7-inch phone won’t see improvements to image quality. The new motors are expected to allow for improved focus time and use power more efficiently than the design used in the iPhone 5s. Even with this concession, KGI still expects the iPhone 6’s picture quality to lead the market:

Compared with conventional open-loop VCM, closed-loop VCM keeps records of focus points, enabling it to produce better quality pictures, focus faster and save power. Nonetheless, there are many factors that affect picture quality, and VCM specification is just one of them. Therefore, we believe overall picture quality of the 4.7” iPhone 6 will lead its peers’.

Both models of the iPhone 6 are expected to enter production next month, as recent hiring frenzies at manufacturing partners seem to confirm, and will be publicly unveiled this fall.