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View Full Version : How to take photos with very long exposures?



sinitry23
01-29-2007, 07:52 PM
How can I take photos similar to the picture below? I understand that you need to have long exposures but does the scene that I photograph needs to be really dark or have very little lighting? Won't long exposures allow alot of light to enter the lens which will make the image look over exposed? Was any filter used on the lens to have this sharp affect? Was this image enhanced from Photoshop?


http://farm1.static.flickr.com/26/94648151_fa963ef368.jpg

More pictures from this link
http://www.flickr.com/photos/rebba/sets/1260435/

kgosden
01-29-2007, 08:44 PM
If you look at the page for the photo you will find a link on the lower right for the camera type and 'more properties' which answers a lot of your questions. On many of the other photos on her site she answers some of your other questions. The page doesn't really differentiate between low natural light and long exposure images. In other words, some of the shots are at dusk or night when there is low natural light. Others are daylight shots forced to longer exposures by adding neutral density filters in front of the lens.

The exposure listed is 6 minutes and the fairly obvious star trails in the image you selected seem to match this. It is not clear if this is just twilight or really at night. Since she did not indicate that she used any additional filters I would guess this is really at the tail end of twilight at best (over 1/2 hour past sunset). Canon's CMOS sensor combined with their image processor, although I believe she shot this as a RAW image, is probably one of the cleanest for long exposures.

The first step in going down this route of long exposures is to buy the best damn tripod you can afford. Heck, you probably need to buy one even better than you think you can afford. You can't take a sharp photo without one.

kgosden
01-29-2007, 08:52 PM
She does have the advantage of very long nights to practice during the Winter in Iceland. In January I would think there is quite a bit of twilight time.

VTEC_EATER
01-29-2007, 09:10 PM
Well, Im not too familiar with long exposures, but from the look of the photos, she has a long depth of field, indicating a high F-stop number, maybe F/11 or F16? Judging by the clenliness of the image, I would imagine she shot at ISO 100 or 200, and if the camera had the option, used "long exposure noise reduction" as one of the settings. Set the image quality to raw for post process cleanup, and let her rip. I dont know if she shot in full manual, or aperture priority. I would imaging the process takes a bit of trial and error, but if you have the time, I say go for it.

Norm in Fujino
01-29-2007, 10:12 PM
Was any filter used on the lens to have this sharp affect? Was this image enhanced from Photoshop?

The image is actually not particularly sharp, but on the contrary pretty soft, a result both of the length of exposure (causing all moving things to blur) and (probably--only a guess) noise-reduction, either from the in-camera processor or afterwards in computer (Noiseware, Neatimage, etc.).
As for the daytime versus nighttime thing, one of her photos (below) is a 36-second exposure at noon using an ND filter.

http://farm1.static.flickr.com/39/106778262_235f2961af.jpg

mattdm
01-30-2007, 01:05 PM
Well, Im not too familiar with long exposures, but from the look of the photos, she has a long depth of field, indicating a high F-stop number, maybe F/11 or F16? Judging by the clenliness of the image, I would imagine she shot at ISO 100 or 200, and if the camera had the option, used "long exposure noise reduction" as one of the settings. Set the image quality to raw for post process cleanup, and let her rip. I dont know if she shot in full manual, or aperture priority. I would imaging the process takes a bit of trial and error, but if you have the time, I say go for it.

Yeah, but rather than guess, you can look at the EXIF info on flickr:

Exposure: 360 sec (360)
Aperture: f/8
ISO Speed: 100
Exposure Program: Manual

I think the sharpness is mostly simply because it's scaled down. You can make anything sharp that way. (Okay, some things you have to scale down to one pixel, but the theory is sound.)

VTEC_EATER
01-30-2007, 02:39 PM
Yeah, but rather than guess, you can look at the EXIF info on flickr:



Thats too easy.

nevilleb
02-01-2007, 04:50 AM
The neutral density filter has already been mentioned, but I'll gloss over it a bit more.

A neutral density filter reduces the amount of light passing through it. They come in two varieties - graduated, and non-graduated.

Graduated ND filters are used to darken the sky, giving a gradation to it, from darker to lighter. The non-graduated ones darken the entire scene in a uniform fashion.

We of course, are dealing with non-graduated nd filters here.

Since these filters cut down the light passing through them, we need to increase the amount of light that falls on the film plane (or, digital sensor) in order to nail the exposure. We can do this in two ways : by opening up the aperture, or, by increasing the exposure time (decreasing the shutter speed).

By using a small aperture in conjunction with a nd filter and a low ISO setting, it is possible to get relatively long exposure periods - depending of course on the brightness of the scene.

This can be carried further - stacking up several nd filters results in each filter cutting down the amount of light, resulting in even longer exposures.

In case one doesn't have more than one nd filter, one can use a nd filter in combination with a polarising filter. A polariser will cut down light by at least two stops - that results in a quardrapiling of the exposure time that would be possible by using just a nd filter.

Keep in mind though that every piece of glass you add in front of the lens will affect image quality. Also, beware of vignetting.

Hope that helps.

michaelb
02-01-2007, 07:07 PM
I have been considering trying some of these long exposure night shots....but is there some rough guide to the right exposre time (shutter speed)? Is the camera's light meter accurate in such situations?

Norm in Fujino
02-02-2007, 12:08 AM
I have been considering trying some of these long exposure night shots....but is there some rough guide to the right exposre time (shutter speed)? Is the camera's light meter accurate in such situations?

In a word, NO. It of course depends on how long the exposure is, but if you're talking about outdoor lighting and star trails, it's trial and error, one of the things that makes photography a craft. This is digital, so you're not wasting any money on film. Just try different times and see what results.