Great to see you here. Join our insightful photographic forum today and start tapping into a huge wealth of photographic knowledge. Completing our simple registration process will allow you to gain access to exclusive content, add your own topics and posts, share your work and connect with other members through your own private inbox! And don’t forget to say hi!
That makes a lot of sense ! Thank you Steve !Hi Stefan,
There is another reason this technology applies to CMOS. Ultimately, the dynamic range could be increased exponentially.
It is because each pixel in a CMOS chip has its own electronics. In terms of what we have now, this is a questionable advantage, as CCD chips intrinsically have a higher DR and less noise than a CMOS chip. Color can be more uniform in a CCD device. Since each pixel of a CMOS chip has its own converter and amplifier, photons coming in are partially blocked by electronics and it is very difficult to match the output of every amplifier on a CMOS chip. The CCD amp and converter each are used for a bank of pixels, so each sees the same electronics, increasing uniformity and accuracy of output.
An advantage of CMOS, though, is that in theory every amp on every pixel can have its gain changed independently in real time, which is not possible with current CCD designs. Dynamic range can be adjusted all across the chip, dialing up gain for shadows and down for highlights on a pixel by pixel basis. Current CMOS chips adjust gain over the entire chip at once, but the opportunity is there to change gain as required for each pixel. Already we see how CMOS chips can have gain adjusted for high ISO use overall compared to CCD, but CMOS pixels allow for individual control as well.
I have read articles suggesting DR increases to over 100 using this technique in the future using CMOS chips.
Hope this made sense,
Steve
Thanks Jan ! Is that about similar as limiting lights (or shadows) at scanning in Software by value ? Guess so ?If the clipping is due to the well saturating, then tweaking the readout design isn't going to make any difference. What you need is modify the photodetector so its sensitivity (here: fill rate) progressively drops as it fills up. It already does, but there may be ways to increase it. With CMOS it should be possible to add decay around the top 2-3 stops (by opening a leak from the well to the drain) to create a shouldering effect. The software has to be aware of this so it doesn't try to determine chroma, because it will be heavily desaturated. I can just let the chroma fade away.