Fogotten your ND filters but want to create a long exposure image

Ken Rennie

Well-Known Member
In my case I had brought my ND filters but they were wet and my lens cloth was just producing a foggy mess.
I was beside a local river that was deep in a gorge and despite this being summer and the middle of the afternoon it was pretty dim and I could get 0.3s exposure at f16 but I wanted a longer exposure. Many years ago I had experimented with the stacking technique and using mean mode but it hadn't worked very well as I had waited between each exposure so instead of a smooth transition between moving elements there was a gap. This time I took automated bursts of 5 images, this is a standard Sony setting. I could have produce more but 5 images at 0.3s should give me the equivalent of 1.5s and I had already seen that 1.3s gave me a nice effect despite the foggy and blotchy look through the ND filter. The upside of using this technique, no need for an ND filter and the ability to produce long exposures when you can't fit an ND eg ultra wide lenses with no filter thread, no colour casts, slightly higher quality with less glass in the way and lower noise as averaging exposures reduces noise. The downside, 5 times as many files and more time spent in front of a computer.
Here is a single image
7032 to 7036 mean merge v2 single.jpg

This is 0.3s shutter speed I probably should have opened the aperture up and shot it at a faster speed to get crisper detail but it is easy to be smart after the fact.

Here are the 5 images stacked and the average calculated
7032 to 7036 mean merge v2 total merge copy.jpg


As you can see it looks like a long'ish exposure but the small falls look soft because 1.5s is too long to show much detail.
Now the clever bit
I merge and mask one of the 0.3 s images into the above stack

7032 to 7036 mean merge v2 final.jpg


I was using a 16mm lens but I wanted a slightly wider image so I produced a pano using the 5 shot technique and here is the final image.

7022 to 7026 and 7032 to 7036 mean merge 1200px.jpg


If you haven't seen this technique a quick google found this.

https://www.wardynskiphoto.com/gallery/how-to-simulate-long-exposures-in-photoshop/

Looking at this image the swirls and trails are a little "choppy" so 10 image at 0.15s should even this out. I will make sure that I have plenty of cloths on my next outing and will compare the 2 methods but and an important but I know that if I want to buy a 12 or 14mm ultra-wide and can't use filters then this technique will enable me to produce long exposures and I do like them a lot. Ken
 
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AlanLichty

Moderator
Very nice result and I like the final variant with the more crisp water flow in the foreground.

I have been using this same stacking technique with waterfall images using my drone since I don't think the drone is stable enough in flight for good details with long shutter speeds of there is any wind.
 

Ken Rennie

Well-Known Member
Alan have you tried producing 2 smart object stacks. One using mean mode and the other using median mode. The mathematician in me thinks that the median mode should give you a sharper shot and you use this for the surrounding rocks and the mean mode for the water. Of course you may well have used this already. Ken
 

AlanLichty

Moderator
Alan have you tried producing 2 smart object stacks. One using mean mode and the other using median mode. The mathematician in me thinks that the median mode should give you a sharper shot and you use this for the surrounding rocks and the mean mode for the water. Of course you may well have used this already. Ken
Median stacking mode with smart object stacks is what I have been using in PS. I have not tried mean mode on the water (yet). I might try that next time I use this technique.
 

Ben Egbert

Forum Helper
Staff member
Neat post and lovely images. I have not yet gotten around to using smart objects, but I have used stacking and mean mode. I need to give this technique a try. but I am usually 1/4 to 1/10 shutter speed.
 

JimFox

Moderator
Staff member
Hey Ken, that's a great trick and you used it to perfection. It sure looks great with your result.

I wrote an article on how to do that years ago, and it can be found in our Article section.

(1) 10 Stop ND Alternative | Focal World

We have a lot of great tips in our Articles, for those who haven't looked at our Articles, please do.
 

Bob Israel

Supporting Member
Just reading this now. Sony had a great little feature that did this all in camera as part of its Play Memories app up through the A7r2 cameras. You could shoot normal exposures at whatever shutter speed fit the scene taking 32, 64, 128 images, etc. The camera app would then compile into one image. ND Filters weren't necessary. Unfortunately, they abandoned Play Memories for the Imaging Edge app and we lost the feature.

Beautiful images!
 
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