D90 Multiple Exposure- Unexpected Results

[robbie_robertson]

<p>I toyed with this function last weekend- The user guide depicts the same woman in three different positions in a single frame. This is pretty easy to do in Photoshop, but I thought I'd see how well the camera did it. I achieved the same results as the picture below every attempt, on either two or three exposures, and with the gain off or on. The gain worked as advertised, where when 'off' the combined image looked about plus one EV over a normal single image, and when 'on' was the same apparent exposure. But the ghost images were a surprise... If this is a firmware issue, I might be tempted to leave it this way: I'm going to a fairly bustling plaza this weekend to experiment with how the finished image looks- I'd have an easier time with this behavior than if I stacked ND filters for a long exposure that would accomplish the same "near elimination" of pedestrians. In this case, the ghost images would be frozen as opposed to appearing as faint streaks on a long exposure. Might be interesting. BTW, I'd love to know if I did something wrong, and has anyone else experienced this?</p><div></div>

[james_lai]

<p>With 3 exposures the background gets 3x as much exposure as the subject. I think the problem is the white background is wiping out the subject.</p>

[steven_oster]

<p>You'll see the same defect in firmware if shot on film. Think about it, the camera is recording the wall behind you 2 times for every 1 time that you are in the example photo. </p>

[alan_huett]

<p>The only way I know of to get around this is to move the "repeated" subject closer to the camera and light it with flash. Then repeat - the flash falloff will result in a background of lower exposure and therefore adding the exposures will generate a properly exposed background with repeated subjects across the frame. Obviously playing with the relative distance between background and subject will be required to get this just right. I guess the same effect is possible with restricted ambient light too, but flash seems easier.</p>

 

[robbie_robertson]

<p>Ok, my question was answered obliquely... The function does not work as defined in both the Nikon user guide and the Magic Lantern Guide. I guess this was a gee whiz moment, but I'm still interested in trying it for "crowd near elimination" in cityscapes etc.</p>

[Dieter Schaefer]

<blockquote>

<p>The function does not work as defined in both the Nikon user guide and the Magic Lantern Guide.</p>

</blockquote>

<p>I disagree - the function works exactly as advertised - you get three exposures in the same image. The fact that you get your "ghostly" appearance is entirely due to the white wall you are standing in front of - the sensor is just adding the light of your three exposures. If you took the same three shots in separate images and added them together, you would get exactly the same effect.<br /> Unless the crowd you are shooting will be wearing all white or there a only white backgrounds - your "crowd near elmination" won't work either.<br>

If you think of the multiple exposures as "adding light" you won't get the unexpected results; they are unexpected because what you do in photoshop is not the same as what you do with multiple exposures in the camera. To create the effect in PS, you will have to do some kind of masking - and the same is true if you were to create the "expected" result in-camera.</p>

[g._v.]

<p>When I have seen this done in the past it has been done with strobe lighting and a dark background.</p>

[CvhKaar]

<p>If you want "crowd near elmination" to get images of buildings/ area's with (almost) no crowd, it would work better when using a dark-grey ( nd2 or 3) filter, and dail in for a long exposure time, that way the people walking by will mostly not appear in your picture because they would be very ünderexposed (unless they stay in 1 place for a longer time) " while the are wil have the right exposure. i have pictures ( on film though ) that seem to be taken in almost empty streets ..<br>

oh , sorry, didnt read the latter part of your post stating exactly what im saying , oh well...</p>