How long to make people etc disappear?

[Robert]

The idea of using ultra-long exposures to erase a crowd from a picture is apealing at times. The question is how long is long enough? Assuming the people are moving around and not standing still.

[Les McLean]

Why not consider multiple exposures to eliminate people. Open the shutter when there are no people in the scene and close it when there are. All you have to do is keep a record of the time exposed in your head, it can be fun. With a little patience you can be creative and have ghosts almost where you wish. Also, if a person is walking across the scene they are unlikely to register but if the are walking toward or away from the camera they will register albeir slightly blurred.

[Robert Kennedy]

Hmmmmm........ That is almost like asking how long a person's legs need to be.

Outside of doing some test polaroids for each shot, I'd say the best way to go would be to go with the longest exposure you can. The idea being that you'd would be going well past the limit where people show up. Kind of like stopping all the way down to ensure an object is in focus.

That said, all the images I have seen that manage this trick are VERY long exposures. Like 10-40 minutes.

It also seems to me (and take this with a grain of salt as I have never done this), that you need the right type of crowd for this to work.

The principal at work here is pretty much the same as dodging in the darkroom. The dodging wand moves around enough that you don't see it on the print.

This won't work though if the wand stays put or is used for too long. At some point it will leave a noticable shadow.

This would seem to apply to crowds.

If one person stands still long enough, they will show up. Likewise, if there are too many people, you won't be able to get the proper exposure for the area they are in. And by this I mean a New York City sidewalk at Christmas type of crowd.

This is of course all relative to your exposure time. If you had an exposure time of say 10 hours the image would able to tolerate more "standers" and a larger crowd.

What you need to do is figure out the limits here and sort of predict the behavior of people. Not easy to do. Which is why I would suggest using the longer exposures when possible. I seem to recall seeing an image of the interior of York Minster taken with a LF camera. It is a gorgeous B/W image of I think the nave. Anyway, the photographer used something like a 40 minute exposure time. Very long. And people did walk through the picture. But the timing was long enough to "erase" them. Now I have been to York Minster several times. People tend to "meander" there. Sort of a slow stroll through the place. Similar to what they do when in a museum. So I'm guessing that 40 minutes will get rid of most passersby. Unless they are VERY determined to stay put.

Of ocurse 40 minutes is a VERY long time and you would need some serious ND filtering for most situations. I am not sure if any ND filters were used in the image I described, although windows were visible in it, so I'd imagine that some filter must have been done. Even if the image was taken in darkest winter in Yorkshire (which is VERY dark). I would expect that in most situations you'd need to do some sort of filtering.

One thing you might want to try is pacing out the area to be shot ahead of time with the crowd. In other words figure out what will be in the image and walk with the crowd to approximate the average amount of time the average person is "in" the frame. You could do this by following someone in the viewfinder, but that might be difficult. Walk the scene, then double your time. Figure that is the longest average time someone will be in the frame. Then work from there. This might be helpful if you need to figure out the best time and don't have an ND 25X on hand.

[Donald Miller]

Obviously this will depend on the scene that you are wanting to photograph. If this is a street scene, what objects are within the scene that will cause an individual to become distracted, stop, and observe. If there is nothing then the time would obviously be less then if one were within an art gallery or a museum for instance. Once you have decided what the scene is and what the propensity of peoply stopping within the scene, I would then meter a white cloth in the lighting conditions that I wanted to photograph in. I would place this value on below a zone I placement and I would then make a selection of film and ND filtration to give me the time that I had determined. Don't forget reciprocity considerations in your calculations since they will alter the actual exposure calculation by several stops at the very least. If my memory serves me correct, I seem to remember those examples of this technique that I have encountered used slow films and ND3 filtration.

[Robert]

I did some math. Between a 3.0 ND filter, a #8 yellow, F/22 and the added time for failure I get about 15minutes for a sunny day. I'm guessing that would be a pretty good test of my bellows and how well made my homemade lensboards are.

You know what it's like in the city. People are always around but they usually are moving.

[Donald Miller]

If your math is correct, (I didn't check it not knowing what film you were using), it would seem to me that the likelihood of gaining exposure of a moving pedestrian would be very small.

[Donald Miller]

The other consideration that has not been addressed in your calculations is will this give you the proper exposure of the scene that you are wanting to photograph?

[Robert]

I just used sunny/16 to get a rough idea of what it would take. Agfa claims 3stops needed to correct for the long exposure. It would seem the smart thing would be to bring a couple of different ND filters. A cloudy day might take forever using the ND 3.0 filter.

[Nige]

can't add anything to the above but I'll add a little story about a exercise I did the other day.

I was taking a pinhole picture of my car and I decided to pretend to wash it during the 2 minute exposure. I wandered around the car waving my arm around pretending to wash the car (which in fat I had just done&#33 which covered about 1min 45secs by the time I wandered in and out of the scene to cover the pinhole. In the resulting image, I only appear in one area where I figure I must have lingered a lot longer than the rest of the time. I'm going to try this again but will have to balance the exposure with the time I take to 'wash' the car a bit better! The overall exposure was good (it was a sunny day) so I guess I'll have to try it on an overcast day to lengthen the total exposure and give me more time to slow my movement down.

[Jim Chinn]

You have probably seen the very earliest of photographs made by people like Henry Fox Talbot and Neipce. They often showed urban scenes completely devoid of human presence. this was not by design but due to the fact that the speed of the emulsion used was equivalent of 1/2 to 2 asa. Coupled with probably some very small apertures for a large plate camera and you had exposures hours long.

Interestingly enough, I was browsing through the most resent issue of Camera Arts at the book store and there was an article about Chip Foreli (sp) and some of his techniques. One image he used a ND filter to reduce exposure by 13(&#33 stops. He was trying to get a night time effect during the daytime. I don't recall the exact length of the exposure but it was probably several minutes. I would imagine that would eliminate any moving people from recording on the film.