Sigma 35mm f/1.4 DG HSM: Quality Control Steps Up (“A1 MTF”)
See my notes on the new Sigma 35mm f/1.4 DG HSM for Canon and Nikon.
There are three requirements for outstanding lenses: fine design, precise manufacturing and inspection that ensures compliance with all specifications. Sigma lenses are born of well-thought-out design concepts and sophisticated, advanced Japanese manufacturing technology: the final clincher is our lens performance evaluation.
We used to measure lens performance using conventional sensors. However, we’ve now developed our own A1 proprietary MTF (modulation transfer function) measuring system using 46-megapixel Foveon direct image sensors. Even previously undetectable high-frequency details are now within the scope of our quality control inspections. The lenses in our new lines will all be checked using this new system before they are shipped.
Thanks to our new sensors, with their extremely high resolution, you can expect our high-performance lenses to be better than ever.
At the heart of the A1 measurement system is the same Merrill Generation 46 Megapixel Foveon sensor in the Sigma SD1 Merrill, and the Merrill Generation DP cameras. The incredible resolution of this sensor makes it perfectly suited to this advanced scientific purpose. The lenses to be measured are hooked up to the image capture device, and the special charts are captured and analyzed using new, proprietary algorithms designed to work in conjunction with the high-resolution sensor. This level of detail analysis is critical for creating lenses capable of meeting the demands of the most detailed image sensors in cameras such as the Sigma SD1 Merrill and the Nikon D800.
As you know, the 46-megapixel Merrill Generation Foveon sensor is APS-C format, capable of both super high resolution and super micro detail. So, in order to test the lenses edge to edge, and corner to corner, to cover the entire 35mm image circle, the first test image is made at the center of the frame, and then the sensor is moved to a corner of the image circle, and repeated for each remaining corner. The data is analyzed and the tester then determines if the lens has met the quality control standards.
And every new lens designed in the Contemporary, Art, and Sports lines will be tested with the A1 device–meaning 100% of the lenses built will be analyzed and approved before leaving the factory in Aizu.
Today’s best-resolving cameras demand lenses with the highest level of optical performance, and using A1 MTF testing on every lens produced ensures the each lens manufactured is up to both the high standards of Sigma and the the demands of the most discerning photographers–and their cameras.
Marketing hype? I don’t think so.
The process sounds great and it no doubt has its limitations— but it is a useful and important validation step. Moving forward to 36 megapixels and beyond in the DSLR arena, more precise quality control becomes mandatory.
UPDATE: I requested MTF charts from Sigma, but my request was not granted. This is unfortunate— when a company is to claim MTF testing, it ought to back up its claims by providing some evidence of it. Zeiss and Leica do (and I trust their charts). Nikon and Canon do (though I don’t trust Nikon and Canon or Sony MTF charts).