Mad Hatter Imagery wrote:
For example if you wanted to long exposure stars, but also there are street lights that would blow out the image?

SHORT VERSION:

I'd suggest looking at blending shots with different exposures instead.  I suspect that may prove to be a much more practical solution to your (fairly extreme) "street lights combined with stars" exposure problem.

I.E.  Multiple shots of the same scene (on a tripod, of course) with different exposures, that are blended together in post processing.


LONG VERSION:

While I've done a lot of model shots that incorporated long exposure (cityscapes) night work, "starry skies" are definitely not in my area of expertise...

However, I recently followed a tutorial (that I can't find at the moment) by an expert in nightscapes which blended wonderful night country scenes (trees, etc) with beautiful starry skies.

My takeaway was that it involved multiple shots of the same scene (on a tripod, of course), that were blended together in post processing.

Not only did you have the wildly incompatible exposure levels (as per your question) but, for an excellent "starfield shot", he had equipment to track the movement of the stars, keeping them "still" for the camera during the long exposure.  Obviously, that tracking movement would completely mess up any lit foreground areas (not to mention street lights!), so...

In his particular case (in a really dark country area), he used some subtle light painting for trees, etc, to get his separate (desired exposure) shots of the foreground area, that he blended with his best "starfield" exposure shots.

One way or the other, I'd suggest looking at blending shots with different exposures instead.  Again, I suspect that may prove to be a much more practical solution to your (fairly extreme) "street lights combined with stars" exposure problem.

Mad Hatter Imagery wrote:
How comparable is a digital sensor to film? Can you control sensitivity after an image is detected? For example if you wanted to long exposure stars, but also there are street lights that would blow out the image? No way to ignore light above a certain level?

Film had less dynamic range than a digital sensor has. Slide film, in particular, has a much smaller dynamic range (I don’t remember the numbers, but something like 5-7 stops?)

There isn’t a way to stop exposure on a digital sensor once it reaches a certain point, excepting, of course, that it stops once it reaches saturation (blown highlight). But you can’t do that with film, either.

Several people have suggested stacking multiple exposures - that’s a solution, and more practical than looking for a sensor with unusual properties.

Frozen Instant Imagery wrote:

Film had less dynamic range than a digital sensor has. Slide film, in particular, has a much smaller dynamic range (I don’t remember the numbers, but something like 5-7 stops?)

There isn’t a way to stop exposure on a digital sensor once it reaches a certain point, excepting, of course, that it stops once it reaches saturation (blown highlight). But you can’t do that with film, either.

Several people have suggested stacking multiple exposures - that’s a solution, and more practical than looking for a sensor with unusual properties.

What if one can select certain light sources that the sensor can ignore all together? Just draw on viewfinder areas to black out?

Mad Hatter Imagery wrote:
What if one can select certain light sources that the sensor can ignore all together? Just draw on viewfinder areas to black out?

In camera?   Short answer:  No.

Camera companies design "in camera" features that they believe there is quite significant demand for.  And, usually, where the market has already PROVEN that such a demand exists.  So you might want to temper your expectations somewhat.

Personally, I suspect that if you talk to those who design the cameras, the first thing they'll say is "that is a post production" issue.  Or, modified to some degree in close to "real-time" with good tethering software (on the computer's side).  But NOT "in camera".  And certainly not editing out parts of the sensor "before the shot"...

Light doesn’t work that way either.  All light sources are emiting  photons, which are traveling in a straight line from their source until they hit  something. The sensor couldn’t know whether a photon was emitted by a streetlight or by the moon. There are such things as sensors that are only sensitive to specific wavelengths  of light and so would “Ignore” a light source not emitting in that wavelength but that’s not what you are describing.

So far  as sensitivity, digital sensors have up to 15 stops of dynamic range depending on the sensor.   Negative film had 7 stops, color negative 5 stops, and transparency film had less than a stop of dynamic range.  Dynamic range being that exposure latitude between no light, so sensor reads black, and too much light, so sensor reads pure white.

For what OP is describing ,  you’d handle that with multiple exposures, multiple frames and deal with it in post.

Mad Hatter Imagery wrote:
Sensor sensitivity?

As I understand things, sensor sensitivity is a physical property of the silicon wafer, it's not variable. ISO changes are created by electronic amplification.