EOS 5D Mark IV Exposure simulation for 4+ minute daytime exposure

[larrylato]

I do both astro-photography and long exposure using ND filters. At some point, when conditions are dark enough, live view exposure sim no longer works. I understand that. Live view is showing what the sensor sees thru the lens. Recently I was on a trip in Mich UP, doing long exposure of a lighthouse during the daytime. Using a 15 stop ND filter on my 24-70 lens, I was shooting a few 4 minute+ exposures when I happened to notice my live view was showing the properly exposed live image. How can that be? If the sensor is looking thru a 15 stop ND where I need over 4 mins to get a proper exposure, how can live view be showing my current composition? This is a DSLR, not mirrorless camera. Thanks much. Larry

[Waddizzle]

When you use Live View mode, your DSLR is essentially operating line a mirrorless camera.  It even has an ExpSIM setting that you can enable.  Your Exposure Simulation may be enabled, or was.

[larrylato]

Thanks and yes I understand that. But with a DSLR, live view is using the sensor viewing thru the lens, not an electronic viewfinder like in mirrorless. How can the sensor "see" thru a 15 stop nd filter? 

[Waddizzle]

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@larrylato wrote:

Thanks and yes I understand that. But with a DSLR, live view is using the sensor viewing thru the lens, not an electronic viewfinder like in mirrorless. How can the sensor "see" thru a 15 stop nd filter? 

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If your exposure settings were adjusted for a proper exposure with the filter in place AND your shutter speed was under 30 seconds, then the camera should be able to simulate the exposure in Live View.

[Tronhard · Accepted solution]

Hi Larry:
First, I am not sure what you were trying to say with  your comment "But with a DSLR, live view is using the sensor viewing thru the lens, not an electronic viewfinder like in mirrorless" but  MILCs can only show what the sensor is seeing as there is no optical viewfinder.
I think that the issue that for both in DSLRs in Live View mode, and MILCs all the time, the image is being read off the sensor, but the critical issue is whether Exposure Simulation mode is being applied.  To refer to the 5DIV Advanced User Guide, P311:

and on P302:

So, my point is that the critical element is in what mode of Exposure Simulation the camera is in, not simply if it is in live view.  As the manual says, there is an option either way and that is true for both DSLR in Live View mode and a MILC all the time.

[larrylato]

Thanks Trevor. So exposure sim is a "representation" of your image based on available light the sensor sees. So even though I needed over 4 minutes to expose the photo properly with a 15 stop filter, the sensor was seeing enough light to support simulation. I find that hard to believe but I guess that is my answer. Thank you all for your help. Larry