Nikon Z6: 30+ second exposures

Started 7 months ago | Discussions thread
beatboxa Senior Member • Posts: 7,011
Re: Nikon Z6: 30+ second exposures
6

DDavis1 wrote:

beatboxa wrote:

DDavis1 wrote:

beatboxa wrote:

Have you been using LENR (Long Exposure Noise Reduction, not to be confused with "High-ISO Noise Reduction)) or dark-frame subtraction?

If not, I'd suggest using these.

Also, if you are struggling with the noise, have you ever considered stacking multiple images rather than using an ND filter?

You are correct about stacking/bracketing images, but I think he's specifically referring to long exposure photography where the use of ND filters for daytime exposures longer than 30 seconds is mandatory.

Stacking / bracketing has the same effect as long exposure photography.

For example, if you took a single 30 second image of a waterfall or stacked 30x 1-second images of the waterfall, or 3000x 1/100th, all results would exhibit the type of motion blur the OP is looking for.

The key is if one did more smaller exposures, they wouldn't blow out the sky in each individual image, so they wouldn't need an ND filter. They could subsequently edit the brightness ranges locally--which is what HDR imaging is.

I saw photographer Hunter Henry sorta using this process where he took two shots of the same composition, but with two different focus points and blended the two into a single shot (not exactly stacking).

The point of using the filters though, is to make that process easier/more streamlined; whether using screw on's or 100mm glass gradual ND's. Especially for exposures of 1, 2, 4 minutes or more, but when you expose for that long, you're going to get hot pixels. Using GOOD filters and having Long Exposure NR turned on for those longer shots is the more streamlined process. The downside to that of course is the amount of time per shot. The LENR process is equally as long as the initial shot took. So, if it was a 4 minute exposure, the LENR will take and additional 4 minutes. Using QUALITY glass filters (more expensive of course) creates some image detail degradation, but is almost damn near imperceptible vs using cheaper filters.

There are pros & cons to each approach. Frankly, the "process being more streamlined" is no longer a thing for digital photography (as opposed to film photography) because there is plenty of software that does all the work today. I'd actually argue the opposite is true in the digital photography world: ND filters require more thought & planning up front and provide more limited results than stacking. Stay tuned on why.

As an example, here is a crop from a dynamic scene, which involves the sky and the ocean:

This was taken at 1/500, F/8, ISO 100 on an APS-C camera.

You'll note it's very noisy in the shadows such that there is no detail. But this exposure is required to keep the sky from clipping due to the sun (which is also in the pre-cropped frame). You'll also notice quite a bit of flare. And that the waves from the ocean are well defined.

So to remedy these issues, one can take several of these images and then stack them. In this case, I took 20 shots, each 10 seconds apart (these were part of a video timelapse I did). This required no additional work: I spend about 10 seconds programming my camera do do all of the individual exposures for me and then hit the shutter button.

So this now has the shutter speed exposure equivalent of 20/500 = 1/25. Still not particularly long. I could have done more pictures at a smaller interval if I wanted as well--it would have resulted in the same thing, with even more information.

Now, I just load them into software and hit "stack" (or whatever button is there). And voila. Here are the results:

Now, we've got plenty of detail in the shadows with almost no noise. The fine detail of the waves has been averaged out (which is precisely what happens during a long exposure). The lens flare has also averaged out and virtually disappeared (since the sun moved slightly between frames). And the sky isn't clipped or in danger of clipping. And now, I can locally adjust each region as I see fit.

And this is because in a single long exposure, we end up with a total sum (like "59"); but in this method, we have all of the line items (like "12+12+12+12+11 = 59").

Remember earlier when I mentioned that ND filters require more thought & planning up front? Here's what I meant: The beauty of this method is I can essentially choose my shutter speed after I've already taken the shot, without worrying about clipping or anything. I could have taken 1000 shots but only decided to stack 10 or 100. I could also have adjusted various regions of the frame locally, like if I actually wanted definition on the trees but not the waves. Etc.

This, btw, is also how the latest & greatest phones work--they do this sort of thing automatically. (They also generally employ some algorithms to track moving subjects, which is not required here since the camera is on a tripod. So in our case, we can just "dumbly" stack them).

All this to say: there are no situations where an ND filter is mandatory, unless the required exposure exceeds the maximum shutter speed / aperture combination of the camera, such as when photographing the sun directly. But in almost all other cases (including waterfalls as sunrise or sunset), this stacking method can be used instead of ND filters, which themselves are more of an antiquated solution to this same problem but for film photography rather than digital photography.

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