D800 Reticulation issues during night photography–white dot problems
- At August 02, 2013
- By paul
- In Articles/Reviews, Nikon Gear
- 0
I have been using the Nikon D800e now for about 10 months in outdoor night photographic work. Recently I have noticed a disturbing issue with the results which I believe look very much like reticulation errors from the old darkroom days. If you over processed a B&W negative during the you could get a coating of very faint white dots on the negative. You can also sometimes get this in the print making but I found it more common on the film processing side. The net result was a ruined image that was covered in white dots. So far in my years working with digital files I have not seen this type of an error. With the D800e I noticed some a few white spots on some of my longer exposures when I first started to use the camera for night work. However they were not very numerous usually only numbering from 10 to 20 total. On my last night outing my D800 really had a problem with this. When you double click on the image shown above you can clearly see the numerous white dots throughout the image.
A bit of history, my night photographic work is done with stacking. I prefer the output from stacking over one single long exposure. If you work with a Nikon on a single long exposure with “long exposure noise reduction” turned on, there is a problem. Nikon like all other camera companies, basically runs a dark frame for the same time as the original exposure. However with Nikon you are locked out of the camera for the duration of the dark frame. So if you shoot a 45 minute single exposure, then after the original shot finishes, you will then have to wait another 45 minutes while the dark frame runs. You cannot take any other pictures or make camera adjustments until the dark frame finished. There appears not to be a buffer that the dark frame can be run in the background. With Canon (at least on the 5D MKII and 5D MKIII) you are not locked out and the dark frame is done in the background in a buffer. You will eventually buffer out after about 3 exposures, where on the 3rd shot you will have to wait for about 20 minutes for the camera to free up, but this is still much better than Nikon’s implementation which is the same as Phase One’s on their medium format backs. I always recommend long noise reduction to be on with single long exposures as there tends to be way too many stuck pixels created and the dark frame will remove these along with some of the base line noise created.
In night photographic stacking where I am shooting to create star trails, dark frame noise reduction creates way too many gaps. An example during a a series of 1 minute 50 second exposures where I might take 25 total frames to get to around 45 minutes I will have only 12.5 total frames of data, the other 12.5 frames will be taken up during the dark frame. Yes there are tools like Star tracer to fix the gaps but to fix this many large gaps really causes some overall problems putting the final image back together since Star Tracer has to really move the file to close the gaps.
When a digital camera gets hot you start to see strong image depredation. With Canon files this seems to show in dark black splotches that can become way to numerous to remove. Traditional dark frame subtraction will not get these out since they are already black. Dark frame subtraction is looking for solid colors (red, green and blue) from stuck pixels, and large areas of noise. So in the past before I started to stack my exposures, once I started to see the black splotches on my images I tended to stop for the night. In Arkansas, where summer temperatures can get 8o to 85 degrees at midnight with high humidity you are limited to just how much your camera can handle. Because of this I prefer the wintertime, fall or springtime to get in most of my work. But it’s still hard to resist a clear night in July and August.
With the Nikon D800e you are taking a file that is approximately 2x larger than the output from either a Canon 6D or 5D MKII, even a 5D MKIII. Canon also offers the small and medium raw output which I often use. The reason being that in night work you are not as concerned about the finest details. I would love to see Nikon offer at least a medium raw size output on their their D800 family of cameras in a firmware update. A medium raw output would be around 20mp in size from the D800 and you might not work the chip as hard as with a full resolution output.
As I mentioned earlier when I first started to shoot with the D800e at night I would always see just a few solid white dots. Never more than 20 and usually around 10. These dots were the size of a normal stuck pixel and easy to remove. Lightroom which normally does a good job at removing stuck colored pixels ignores these however and I had to go into the file and manually remove the. I did notice a slow increase in the numbers of these “stuck” white pixels but they were never a big deal. On my last night shoot with the D800e I did start so see many hundreds of smaller white dots. They were about half the size of the stuck pixels sized dots but way more numerous. You could see them on a 100% review of the image on the LCD of the D800e. When I returned to my studio and started to work on the files I found that these white dots numbered more in the thousands. Way too many to manually remove.
The dots are small and faint but depending on the conditions where you shot the stars but if you are stacking then they really pose a big problem. This is because with all stacking, you tend to get faint gaps between the start trails. The gaps can become larger, if you briefly stop the stacking process to check your exposure. On a 45 minute or longer stacking series, I will tend to stop the camera several times to check my exposures to make sure for example the moon has not started to create destructive flare, or due to the amount of moonlight I need to increase or decrease my shutter speed/iso setting. To close up the gaps, I use a software tool call Star Tracer and it does a great job. However the way it closes the gaps is to move the image up and down slightly and by this it moves the star trails over the gaps closing them. If you have dots or stuck pixels, you will see the dots take on a stepping pattern the number of steps is determined by how many times star tracer had to move the actual file. This creates a dotted line throughout the image and can ruin the image. The only way to fix it is to manually remove as many of the dots as possible before you run Star Tracer. Here is a closer view of the problem areas in one of my shots.
After first seeing this, I found that I could remove about 1/2 of the problem dots by increasing the amount of noise reduction I was using on the file. In Lightroom I increased the noise detail slider, the color noise slider and the overall luminance slider. This in effect blurs the dots enough many of the more faint ones will not show up. Since I also stack the images in Photoshop I run both a maximum and mean stack mode and then combine the two. By combining these outputs you can reduce the number of dots by as much as 1/3 more. I also have found that by using Capture One instead of Lightroom I can remove almost all of the dots since Capture One has a different noise algorithm which seems a bit more sensitive to this type of problem. Capture One also offers “single pixel noise reduction”.
I also ran the same D800 Raw files through Capture One version 7 and with the single pixel noise reduction slider moved to about 50 percent these dots are almost all removed. On this particular shot the moonlight was also causing a similar issue that one sees when using a circular polarizer. The lens I was using was the Nikon 14-24 @ F3.5 and the sky consistently was darker in the center than on the sides. This is not classic vignetting, as the amount of light and dark areas far exceeded normal vignetting. Here is a small shot from a Capture One processed image.
Capture one actually processed out the files quite a bit easier than Lightroom 4.4. I tend to still lead with Lightroom 4.4 with my D800 shots especially the night shots. This due to the fact that Capture One tends to have a bit more problems with the blue hue of the night sky which is due to the moonlight. Capture one does apply a bit more noise reduction to the files than Lightroom as a default. This will generate a very clean sky, but tends to make trees and rocks a bit tool soft. This is not really a big issue since I am stacking and generally only will use one image’s foreground for the final output. It’s very easy to go back and reduce the amount of noise reduction and then re-output the file. On these images where I was working with about a 4/5’s moon, Capture One was able to pull out quite a bit more of the distant stars than Lightroom. Here is an side by side showing the difference the noise reduction settings can have on the more detailed parts of files in Capture One.
I am hoping that this issue does not get worse, as if it does I will have to send the camera back to Nikon to see if they can determine what might be causing the problem. So far I have only seen this type of noise in my night shots, however they seem to show up even in the lower iso ranges of 200 through 400. As I only own the (1) D800, I can’t state that this is an issue with all Nikon designs or if it’s just an issue with my D800e or all D800e/D800 cameras. In May when I last shot the D800e at night the ambient temperatures were about 82 to 75 degrees which should not be that much of an issue. I would expect this more in temperatures of around 87 to 96 degrees.
The other option would be to try the D800 on a single long exposure with the long noise reduction on. This would limit me to about only one shot per night, maybe 2. Or I might try to stack with the long noise reduction on and see if I can get Star tracer to close up the gaps. Either way it’s a major inconvenience.
03/13/13 Featured Arkansas Photography–January Night skies over Roark Bluff
- At March 11, 2013
- By paul
- In Featured Arkansas Photography
- 0
Taken with a Nikon D800e, Nikon 14-24 lens @14mm F 4.5, iso 400. Image taken in a series of 2 minute exposures and stacked to capture motion. This was my first trip with the Nikon D800e for night photographic capture. I had used the D800e throughout the 2nd half of 2012 but was never able to coordinate a good night for a shoot. I prefer to have a clear night with a 1/2 to 3/4 moon and on the 20th of January in 2013 all of this came together. There was also very nominal wind for the entire night. This particular shot was taken looking downstream so I can featuer Roark Bluff and still capture Bee Bluff, the next bluff down river. All of the on the bluff and riverside trees is from the moon and no light painting was needed. The moon is a wonder ally with night photography, giving you a great blue hue to the sky along with adding just enough illumination to see the foreground details i.e. bluff, trees, etc. I was very pleased with the results of the D800e at night. The 14-24 lens at F4.5 still was extremely sharp and the corners of the shot were very useable. I noticed no coma in the stars and very little chromatic aberration. I used Capture One 7 to convert the raw files and stacked them in Photoshop CS6 to capture the star motion. I then combined various versions of the foreground image until I got the best overall image.
02/21/2013 Featured Arkansas Photography–Night skies over Twin Rivers Park
Taken with a Nikon D800e, 14-24 lens@ 17mm, F4.5, iso 400. Image is the result of a series of 35 second frames that were stacked together. Well, it’s been a while since I put up anything new, and I do have my reasons, but I am going to try and get a bit more current. This shot was taken over the new bridge at Twin Rivers Park, in Little Rock. This is a new subject for me but one I have wanted to explore for a while now. The bridge has a series of bright lights that run along it’s course so it added an additional challenge for any type of shooting. If you exposed the bridge for 35 seconds, it would be totally over exposed, but I need the 35 seconds for the stars. So the solution is to expose a series for the bridge after the stack is done, then combine the images together later. The bridge added one other problem in that it had a much brighter center that would go off like a search light every once and while. You can still the effect in the center of the image, but I felt it was balanced enough as I had it. The effect of the center light is a bit harsher in the smaller jpg file I have uploaded for the web. I was blessed to be shooting with Dr. Smith that night and only to have a few planes overhead.
07/23/12 Featured Arkansas Photography–Lightening Strike over Pinnacle Mountian in Pulaski County Arkansas
- At July 22, 2012
- By paul
- In Featured Arkansas Photography
- 0
Taken with a Canon 5D MKII, Canon 24-70 Lens at 24mm, F2.8, Bulb exposure, tripod mounted camera. This image will be added to my favorites, mainly because of just how hard it was to take. I had been photographing the sunset from the other side of Pinnacle mountain when this storm started to blow in. The early lightening drove me off and I headed around to the west side hoping to get a shot of lightening over the mountain. By the time I made it over, the rain was starting to fall and lightening was flying all through the air. At first I thought I could stand outside my car, with my tripod and take the shot, but soon I started to notice my arm hairs standing up so I choose to move back to my car. I put the tripod outside the car window and then setup my remote release so that I could hit the shutter when I first started to see lightening out of the corner of my eye. I just set the lens to infinity and F2.8 hoping to get the most light as possible. I captured this shot on the 3rd attempt. What amazed me was the different colors of blues that were in the sky as the lightening went off. The orange color off to the left of the image I didn’t notice until I looked at the shot.
07/05/12 Featured Arkansas Photography–Night skies over the Narrows on the Buffalo River
- At July 05, 2012
- By paul
- In Featured Arkansas Photography
- 0
Taken with a Canon 5D MKII, Canon 14mm lens, iso 250, F 5.3, for 35 minutes. Not the easiest place to get to now, due to the flooding that occurred in 2010. The Narrows is a unique part of geography in Arkansas. On one side you have the Buffalo River and off in the distance, Richland Creek. Richland runs into the Buffalo not far from here, but way back hundreds or thousands of years ago, Richland ran right up along the other side of the Narrows and the two streams almost met!. The ledge is only about 2 feet wide in places and it’s quite place to walk. The view downstream featured Skull bluff and then around the bend is Woolum Ford. Be careful if you try to get to the narrows or “nars” as the locals call it by crossing the Buffalo at Woolum ford. The actual ford has changed quite a bit over the past few years and is deeper and a bit tricky at most water levels. Due to the excessive drought Arkansas has going right now, it may dry. Once you cross the ford be VERY CAREFUL IN THE SAND. This is great place to get stuck!. The best way is to use 4 wheel drive and go straight up the hillside and cut across the field, don’t try to stay in the ruts as they are now full of sand and very tricky. Even with four wheel drive.
Read More»06/26/12 Featured Arkansas Photography–Stary Sky over Pinnacle Mountain and Area 51
- At June 26, 2012
- By paul
- In Featured Arkansas Photography
- 0
Canon 5D MKII, Lens Canon 16-35 @ F4.5, Iso 250, Exposure approx 45 sec (single image). This image was taken in a series of photographs in a process called stacking. This is one method working night scenes where you are trying to capture star trails. I have found this to be the best method when working with the moon. The moon will provide excellent illumination to the extent that you can get a scene that looks almost like daylight except for the color of the sky. The sky will take on a deep blue color, the blue is very dependent on both the amount of time you expose each stack and the amount of moonlight/position of the moon in the sky. I have found that this type of photography, even though it takes a lot of processing in the background is my favorite way to capture a night sky.