Lets talk long exposure

anonymouscuban

So I recently posted a couple of long exposure shots. I had a friend ask me if there is a point of diminishing return when it comes to exposure time. In other words, is there a point where a longer exposure won't really yield anything different/better.

I told him that I don't have a lot of experience since I do portraiture but that I think it would be very dependent on the movement you are shooting and how you want to capture that movement. I would imagine that movement that is very linear would be better captured with a shorter long exposure. Where movement that is more chaotic, like a beach scene could look great with a very long exposure. Also, if the movement you are capture is very slow, then again, it would require a very long exposure.

What say you all?

fool4thecity

It's all about the movement your trying to capture; right? How fast is it? How much ambient light is available? How long of an exposure? Too long - burned out highlight, Too short - too dark, but its always what is appealing to your eye that counts. Its been done to death, but I still love images of a long exposed waterfall...

Cornflake

In most situations, the question's pretty academic for me. I use a nine-stop ND for long exposures. I don't have a range of very dark NDs. It's that one or nothing. If I use it, it will take as long as it takes.

At dawn, there's more latitude for varying exposure time naturally. Except when I was trying to capture car trails, I've never gotten an exposure that seemed too long.

anonymouscuban

fool4thecity wrote: »

It's all about the movement your trying to capture; right? How fast is it? How much ambient light is available? How long of an exposure? Too long - burned out highlight, Too short - too dark, but its always what is appealing to your eye that counts. Its been done to death, but I still love images of a long exposed waterfall...

I think everything has been pretty much done to death, right?

My question wasn't so much about exposure... it's a given the exposure time has to yield a correctly exposed image. All things being equal, I guess the point of diminishing returns when it comes to shutter is going to come down to the speed of movement you are capturing. Its logical I guess.

Cornflake wrote: »

In most situations, the question's pretty academic for me. I use a nine-stop ND for long exposures. I don't have a range of very dark NDs. It's that one or nothing. If I use it, it will take as long as it takes.

At dawn, there's more latitude for varying exposure time naturally. Except when I was trying to capture car trails, I've never gotten an exposure that seemed too long.

HA. I always say that often times, having choices just complicates things!

Stumblebum

For most needs, highest stop ND filter would be great, why I am aiming for 10 stop filter based on our previous discussion.

However, variable density can be useful too. Sometimes one may not want to switch to bulb mode and in my camera in non-bulb mode, there is 30 second exposure limit. Reason being in bulb mode you may have to take few exposures to get idea where one needs to be but by that time light may dwindle away.

Also if you are trying to create dramatic pictures with people-blur etc, depending on your need to slow down shutter to what is pleasing, variable ND may come in more handy. Of-course there are other way to achieve the same exact result.

Finally, even if you are in bulb mode, when it is late in blue hour after sunset, just before your auto-focus stops working all together, sometimes even 5 minute exposures come out as under-exposed. However, by the time you realize that the light is gone and post-processing has limitations as it can not create information that is simply not there. In that event variable ND would allow you to gather light faster when it is about to dwindle away.

My 3 cents! Cheers!

anonymouscuban

Good points Stumblebum.

I currently own a 10-stop ND filter and a few GND filters of varying stops. I go between using GND filters and taking bracketed shots and blending manually in post. I get mixed results from both. Sometimes, I hit the shot in one exposure using my GND filters. Other times, I get better results from blending exposures. Have yet to figure out if there are any constants to determine the why and whens I should use each method. It really is more about if I'm being lazy or I didn't have my filters with me.

As for bulb mode, although I haven't yet shot anything using bulb mode, I just got a intervalometer and plan to do so during my next outing. That being said, I don't think figuring out your exposure time should be left to guess work when shooting in bulb. You can easily meter without the ND filter, then calculate your exposure time needed when the ND filter is applied.

So lets say you're shooting at f/11 and without the ND, exposure time needed is 1/60 second. Add a 10-stop filter, your exposure time should be 15 seconds. Add an 8-stop filter, now your exposure time is 4 seconds. It's simple math.

If you don't want to do math in your head, you can find tons of exposure time conversion charts on the web that you can print and keep with you. OR... download the app for it. I have a free Android app on my phone called "Exposure Calculator" that works real well and is quite easy to use.

You do make an interesting point that I have never considered and that is that with really long exposures, light can change during the exposure enough to cause the image to be over or under exposed. Say shooting a 5 min exposure right at sunset, light can change dramatically in that 5 minutes so your shot may end up underexposed if you don't account for that change and doing so has to be rather tough. At least from my noob perspective.

Stumblebum

anonymouscuban wrote: »

Good points Stumblebum.

I currently own a 10-stop ND filter and a few GND filters of varying stops. I go between using GND filters and taking bracketed shots and blending manually in post. I get mixed results from both. Sometimes, I hit the shot in one exposure using my GND filters. Other times, I get better results from blending exposures. Have yet to figure out if there are any constants to determine the why and whens I should use each method. It really is more about if I'm being lazy or I didn't have my filters with me.

As for bulb mode, although I haven't yet shot anything using bulb mode, I just got a intervalometer and plan to do so during my next outing. That being said, I don't think figuring out your exposure time should be left to guess work when shooting in bulb. You can easily meter without the ND filter, then calculate your exposure time needed when the ND filter is applied.

So lets say you're shooting at f/11 and without the ND, exposure time needed is 1/60 second. Add a 10-stop filter, your exposure time should be 15 seconds. Add an 8-stop filter, now your exposure time is 4 seconds. It's simple math.

If you don't want to do math in your head, you can find tons of exposure time conversion charts on the web that you can print and keep with you. OR... download the app for it. I have a free Android app on my phone called "Exposure Calculator" that works real well and is quite easy to use.

You do make an interesting point that I have never considered and that is that with really long exposures, light can change during the exposure enough to cause the image to be over or under exposed. Say shooting a 5 min exposure right at sunset, light can change dramatically in that 5 minutes so your shot may end up underexposed if you don't account for that change and doing so has to be rather tough. At least from my noob perspective.

Thanks! Calculating right exposure before hand with filters is something I have not considered previously. Another factor is that usually I am ignoring suggested reading from the camera. However, starting point will definitely come in handy. I will have to work on that! So far I have been taking shots and adjusting based on what I got.

anonymouscuban

Stumblebum wrote: »

Thanks! Calculating right exposure before hand with filters is something I have not considered previously. Another factor is that usually I am ignoring suggested reading from the camera. However, starting point will definitely come in handy. I will have to work on that! So far I have been taking shots and adjusting based on what I got.

I'm no expert when it comes to Landscapes but I do know my way around a camera and exposure. You should be able to calculate the exposure time needed with the ND filter on from a shot taken without it.

I will post my results when I try this next time. Maybe this weekend.

Cornflake

"You do make an interesting point that I have never considered and that is that with really long exposures, light can change during the exposure enough to cause the image to be over or under exposed. Say shooting a 5 min exposure right at sunset, light can change dramatically in that 5 minutes so your shot may end up underexposed if you don't account for that change and doing so has to be rather tough." All true. I've found, though, that I can pretty well guess how long to adjust the exposure, and the results are usable.

For iPhones, I recommend the ND Calc app. Costs one dollar and it has a timer. I know it's just math, but the fractions of a second involved make the math hard to do in your head at times.

Stumblebum

Cornflake wrote: »

For iPhones, I recommend the ND Calc app. Costs one dollar and it has a timer. I know it's just math, but the fractions of a second involved make the math hard to do in your head at times.

Thanks Don!

anonymouscuban

Cornflake wrote: »

"You do make an interesting point that I have never considered and that is that with really long exposures, light can change during the exposure enough to cause the image to be over or under exposed. Say shooting a 5 min exposure right at sunset, light can change dramatically in that 5 minutes so your shot may end up underexposed if you don't account for that change and doing so has to be rather tough." All true. I've found, though, that I can pretty well guess how long to adjust the exposure, and the results are usable.

For iPhones, I recommend the ND Calc app. Costs one dollar and it has a timer. I know it's just math, but the fractions of a second involved make the math hard to do in your head at times.

Cool Don. I don't have an iPhone. Android guy here but certainly helpful for those that do.

anonymouscuban

Thought I'd share this simple shutter conversion guide I found on the net to convert shutter speed without a 10-stop ND to with it on:

Stumblebum

anonymouscuban wrote: »

Thought I'd share this simple shutter conversion guide I found on the net to convert shutter speed without a 10-stop ND to with it on:

I like cheat sheets. Without any filters, in dying light I am usually clipped at 30 seconds, max my camera can do in no bulb mode.

I think ISO and f-stop must be a factors here as if 8 second exposure requires 128 minutes, then I shudder at the thought of what 30 second translates too.

As mentioned previously, I use camera metering as "suggestion" or "starting point" and rely on test shots and gut feeling. Probably not a technique I can publish a paper for but it kind of works.

With 8-stop filter, in dying light with f-16 narrow aperture ideal for my lens/landscapes and with ISO of 100, I would say 10-12 minute exposure works for me. Rest can be adjusted in post-processing as long enough light was capture and soft-ware has something to work with. It can't replace what doesn't exist.

Cheers!

anonymouscuban

So the chart above assumes the f-stop and ISO remain constant. So if at ISO 100 and f-stop of f/8 requires 1/30 of sec to get proper exposure, then adding a 10-stop ND would require a 30 sec exposure... again, with the same ISO and f-stop.

And to your point of what a 30 sec exposure without ND would require with one... it would require a 480 min exposure. And that brings me back to my original question that spawned this thread... At what point is there no increased return, as far as aesthetic quality in the photo, when it comes to length of exposure.

So lets say you're shooting a photo of a seascape... there has to be a certain point in length of exposure where going longer doesn't yield any appreciable difference in the shot. And I also have to assume that there is a sweet spot... that going longer will actually be detrimental to the quality of the shot. I guess this latter point is all subjective and up to the shooters creative differences.

Stumblebum

anonymouscuban wrote: »

So the chart above assumes the f-stop and ISO remain constant. So if at ISO 100 and f-stop of f/8 requires 1/30 of sec to get proper exposure, then adding a 10-stop ND would require a 30 sec exposure... again, with the same ISO and f-stop.

And to your point of what a 30 sec exposure without ND would require with one... it would require a 480 min exposure. And that brings me back to my original question that spawned this thread... At what point is there no increased return, as far as aesthetic quality in the photo, when it comes to length of exposure.

So lets say you're shooting a photo of a seascape... there has to be a certain point in length of exposure where going longer doesn't yield any appreciable difference in the shot. And I also have to assume that there is a sweet spot... that going longer will actually be detrimental to the quality of the shot. I guess this latter point is all subjective and up to the shooters creative differences.

I think longer exposure will overexpose the shot and will blow it out. I have seen shots posted here that turned night into day. So I don't that going longer won't impact exposure negatively. At some point it will. Only issue is how long to expose the shot so it is properly exposed without noise. In long exposures I have noticed that it is very hard to get detail out of underexposed dark area and turns into noise. So getting the darkest area in the shot correctly would get my priority. If something is slightly over expose, it would be possible to recover detail. Dark-area-noise has been what I have struggled with. Others may have different experience/opinion.

PrevailingConditions

Although I mostly lurk around here, I find this thread pretty interesting since I've been playing with some long exposure work. I would say that it all depends. If you're shooting water, then yes, you're going to reach a point where it just blurs out completely and a longer exposure isn't going to add much. Alternatively, if you're trying to capture star trails, then a longer exposure gives you better trails. My last outing I was trying to catch clouds moving and going too long would just give me a boring uniform sky. Get the right length and the exposure shows the motion.

The other challenge is that the exposure can change over the course of 60+ seconds. I've had cases where I metered for the situation, factored in the ND filters and started the shot only to have the sun come out from behind the clouds and blow out the highlights. The reverse can also happen. This is another good reason to check the histogram after every shot.

A couple samples:
#1


#2


Thanks,

Mike

Stumblebum

Good stuff Mike! My exif reader says no info so if you could share it that would be awesome!

PrevailingConditions

Stumblebum wrote: »

Good stuff Mike! My exif reader says no info so if you could share it that would be awesome!

Yeah, flickr has the bad habit of stripping EXIF data.

Anyway, they were shot with a Canon 6D and a 17-40 lens, I think at 17mm for both. ISO 50, f/14 and 60 seconds on one and 90 seconds on the other. I had stacked a 10 stop and a 4 stop ND filter to get the time I was looking for. Hope that helps.

Thanks for the response.

Mike

Stumblebum

PrevailingConditions wrote: »

Yeah, flickr has the bad habit of stripping EXIF data.

Anyway, they were shot with a Canon 6D and a 17-40 lens, I think at 17mm for both. ISO 50, f/14 and 60 seconds on one and 90 seconds on the other. I had stacked a 10 stop and a 4 stop ND filter to get the time I was looking for. Hope that helps.

Thanks for the response.

Mike

It certainly does help! Thanks! Them clouds were in a hurry!!! Cheers!

anonymouscuban

Those clouds were certainly on the go!!!

PrevailingConditions

Stumblebum wrote: »

It certainly does help! Thanks! Them clouds were in a hurry!!! Cheers!

Yeah, the wind was at 20-30 mph on this particular morning. So in addition to trying to get the exposure right, I was also trying to keep the camera from being blown around or getting wet from the occasional shower. Small wonder I had the place to myself . I saw one person start to walk out on the walkways, but fairly quickly turned back. Otherwise I would have been inclined to ask them to sit on the bench - I think it would have made a better shot.

Thanks!