Use an ND filter with fireworks?

[Roger]

I have no idea what prompted me to think about this issue, (prob thinking about using Blue Dot in Feb) but what do you think the results would be using an ND filter for fireworks, such as Wishes?

Now, back in the day, it was too easy with film - f/8, ISO 100 film, bulb exposures to get a few bursts in, and voila, exposure WNL.

But with digital, you have to expose for the scenery and work back from there, because if you blow out the exposure - you've blown it out. I've looked at some of my last shots, and it was ISO 200, f/8, 4 secs. Now I would probably keep ISO 200 (HTP low limit), but what if I wanted 6 or 8 seconds? The bursts themselves are bright enough to be exposed even through a ND filter, but the static elements would need more time. What you would be able to get is more bursts in one shot.

Granted I should have thought about that when I decided to try slides.

<img src="http://www.themeparkphotos.us/cpg140/albums/uploads/052307/D/believe0707200032a.jpg" />
Believe...There's Magic in the Stars (DL 45th)

Worse, it was Velvia. Exposure WNL becomes exposure critical, I think even more so than RAW digital.

What do y'all think?

 

[mSummers]

I don't think the ND is necessary for fireworks. If you are shooting ISO 200 at f8 and 4sec, If you needed 6sec, you would leave the ISO at 200 and change the aperture to f9.5 (the half stop between f8 and f11). Because the difference between 4sec 6sec is 1/2 stop (letting in 50% more light) you would need to decrease the aperture by 1/2 stop to compensate, resulting in the same exposure. That's how I take all of my fireworks photos when I have a background or foreground that I want properly illuminated like these:

http://www.pbase.com/msummers/image/82459778/medium.jpg

http://www.pbase.com/msummers/image/84382307/medium.jpg

Plus, taking the ND on and off all the time would be time consuming and may cause you to miss shots. Just my 2¢ worth.

 

[Dan]

I don't think the ND is necessary for fireworks. If you are shooting ISO 200 at f8 and 4sec, If you needed 6sec, you would leave the ISO at 200 and change the aperture to f4.8 (the half stop between f4 and f5.6). Because the difference between 4sec 6sec is 1/2 stop (letting in 50% more light) you would need to decrease the aperture by 1/2 stop to compensate, resulting in the same exposure. That's how I take all of my fireworks photos when I have a background or foreground that I want properly illuminated like these:

Did you get that backwards? You SAID decrease the aperture, but in your numbers your opened it up.

I have a speculative comment to add. In astrophotography I've heard it said that the brightness of point lights (stars, things that appear as a single bright point with no apparent surface area or shape) isn't controlled by the aperture so much as the ratio of the aperture to the focal length.. or something like that. The point there was that by closing down the aperture you can cut back on things like light pollution but still get bright stars. The thing is that also would cut down on the brightness of nebulas or galaxies too.

I'm wondering if fireworks might have a similar effect. You clearly do get visible width from firework trails, but I wonder if closing down the aperture would tend to narrow the trails, not exactly because you're cutting back on the exposure and making them appear dimmer (or reducing the blown out pixels, blowing out can cause pixel bloom which would make trails appear wider as well), but perhaps the glow of the firework light on the smoke trails is reduced while the fireworks themselves may still have what looks like a point light source in the center that will remain.

I may be stretching things here, but it's something that just occurred to me when I was looking at these fireworks trails.

 

[Dan]

I just realized something. Roger, if you're shooting ISO 200 and want to cut back on the exposure, why isn't reducing the exposure to ISO 100 an option?

I know that the 20D and 30D were known to get more dynamic range at 200 than 100, but that can't be a factor on the Mark 3, can it? Or am I reading too much into this and you just wanted a factor that can be changed in smaller increments?

 

[mSummers]

Did you get that backwards? You SAID decrease the aperture, but in your numbers your opened it up.

Oops... I swear I'm slightly dyslexic sometimes... Anyway I fixed that post to show the 1/2 stop change as being f8 to f9.5.

I'm wondering if fireworks might have a similar effect. You clearly do get visible width from firework trails, but I wonder if closing down the aperture would tend to narrow the trails, not exactly because you're cutting back on the exposure and making them appear dimmer (or reducing the blown out pixels, blowing out can cause pixel bloom which would make trails appear wider as well), but perhaps the glow of the firework light on the smoke trails is reduced while the fireworks themselves may still have what looks like a point light source in the center that will remain.

That's an interesting theory... Maybe someone with two cameras could do a test...

 

[Roger]

I just realized something. Roger, if you're shooting ISO 200 and want to cut back on the exposure, why isn't reducing the exposure to ISO 100 an option?

I know that the 20D and 30D were known to get more dynamic range at 200 than 100, but that can't be a factor on the Mark 3, can it? Or am I reading too much into this and you just wanted a factor that can be changed in smaller increments?

HTP cuts off 100 and 6400 to get more DR on the highlight side. Nikon seems to have figured that out too - if I recall the D3 starts at 200, and 100 is an 'expansion'.

For something where the chances are greater to blow out highlights, I'll use HTP on my blue dot special. Hey the 40D has it and the upcoming 5Dn/6D/3D will have it too.

 

[Roger]

I'm wondering if fireworks might have a similar effect. You clearly do get visible width from firework trails, but I wonder if closing down the aperture would tend to narrow the trails, not exactly because you're cutting back on the exposure and making them appear dimmer (or reducing the blown out pixels, blowing out can cause pixel bloom which would make trails appear wider as well), but perhaps the glow of the firework light on the smoke trails is reduced while the fireworks themselves may still have what looks like a point light source in the center that will remain.

I may be stretching things here, but it's something that just occurred to me when I was looking at these fireworks trails.

Bingo.

 

[WDWFigment]

Did you get that backwards? You SAID decrease the aperture, but in your numbers your opened it up.

I have a speculative comment to add. In astrophotography I've heard it said that the brightness of point lights (stars, things that appear as a single bright point with no apparent surface area or shape) isn't controlled by the aperture so much as the ratio of the aperture to the focal length.. or something like that. The point there was that by closing down the aperture you can cut back on things like light pollution but still get bright stars. The thing is that also would cut down on the brightness of nebulas or galaxies too.

I'm wondering if fireworks might have a similar effect. You clearly do get visible width from firework trails, but I wonder if closing down the aperture would tend to narrow the trails, not exactly because you're cutting back on the exposure and making them appear dimmer (or reducing the blown out pixels, blowing out can cause pixel bloom which would make trails appear wider as well), but perhaps the glow of the firework light on the smoke trails is reduced while the fireworks themselves may still have what looks like a point light source in the center that will remain.

I may be stretching things here, but it's something that just occurred to me when I was looking at these fireworks trails.

When I shoot fireworks shows at f/22 or so, this is fairly noticeable. I prefer the look. I think it's cleaner. As for the ND filter, what is the point? If you're only stopped to around f/9, why not just keep closing it up? Because you want to stay in the 'sweet spot' of the lens? I really can't think of any other reason unless this is why? The fireworks themselves are going to look sharper with a higher number, so unless you don't like the look, why not just do that and not mess with the ND filter? Am I missing something?

Just sounds like a hassle to me. Same with doing it in bulb mode. If I set my camera to 15-30 seconds with f/22, all I have to do is periodically hit the remote. This allows me to pay attention to the fireworks, and just let the camera do its thing. The finale will be blown out, but oh well, at least I didn't miss the show playing with the camera. Then again, I don't even attempt to meter fireworks shots (since I have no idea how), so I just guess and go with what I think will work.

 

[Roger]

Because diffraction sets in very early with digital sensors and you start losing sharpness at the very narrow apertures. The smaller the sensor the lower f-stop before you start losing sharpness due to diffraction limits rather than lens limitations...

Plus the sweet spot of the lens varies, but is usually 2-4 stops down from max.

http://www.cambridgeincolour.com/tutori ... graphy.htm


So with an ND filter you can have a larger aperture but longer exposures....

 

[WDWFigment]

Because diffraction sets in very early with digital sensors and you start losing sharpness at the very narrow apertures.  The smaller the sensor the lower f-stop before you start losing sharpness due to diffraction limits rather than lens limitations...

Plus the sweet spot of the lens varies, but is usually 2-4 stops down from max.

http://www.cambridgeincolour.com/tutori ... graphy.htm


So with an ND filter you can have a larger aperture but longer exposures....

Well, that makes sense then. For me, at least, the ease of using a more wide open aperture is still going to trump. If I were shooting fireworks with a different focal point (such as the statue shot above), I will reconsider. But if fireworks are the primary focal point, is the loss really material? The fireworks themselves will be more crisp for the reasons stated above, and little lines of light aren't "detailed" per se, so it's not a big deal.

However, I may think differently about my castle fireworks shots. The castle is prominent enough for the loss in detail to matter. Thanks for the helpful link, Roger.

 

[Roger]

Np.

I used to shoot the castle fireworks using ISO 100 print film, f/8, bulb mode. Usually 6-8 sec. exposures. It was enough to expose the castle, but thanks to film reciprocity, the castle almost never got blown out. Digital however, that is a huge problem.