The very first photo taken by me on Wednesday evening with a brand new Nikon D80 was of my wife. After that, I started to shoot dark frame test shots. Compared to my earlier dark frame tests of D50, the results were rather disappointing so, Thursday evening I shot another dark frame series. I shot the series simultaneously on D50 and D80. I set both cameras to manual focus, bulb, ISO400 and used IR remote to trigger both at the same time. To start with, both cameras were at room temperature. NR turned was set to OFF in both cameras. According to D80 manual, minimum noise reduction is always performed at ISO400 and above. D50 manual does not mention this but, (possibly) only because D50 has no HI ISO NR option and I suspect that some NR is always performed in it.
First surprise came right at the moment I pressed remote. D80 reacted much faster than D50 even that the remote sensors of the cameras were only about an inch apart and both were facing the remote. because of it, if you check EXIF in the images below, you will see that the actual exposure lengths for the corresponding images vary by tens of a second. The values that are list are rounded. Also, you may notice that the time stamp on images is different by a fair bit. It is so because I don't have (yet) D80 clock synchronised - Nikon Camera Control Pro that can perform the sync is not (yet) compatible with the D80!
I shot a number of frames at exposure times ranging from under 2 minutes to about 20 minutes.
D50 on the left, D80 on the right. Why such a difference in size? Well, the samples that you see below were scaled by the same % from the originals. What you see is really the difference between a 6MP and 10MP sensor.
The first shot was ~16 seconds
Clean images above so, I let the cameras rest for 1 minute before the 526 seconds exposure
In the D50 (left) image above, you can't really see any amp noise at this scale but, at full size, a bit of it was visible. D80 (right) image looks really bad, right? The amp glow is the largest I have ever seen! Well, that's not the end of the surprises!
After only 10 seconds rest for the cameras I shot ~310 second frames
Even that the cameras didn't have much time to really cool down, the glow is much smaller. In fact, it's almost invisible in the D50 image even when watched at 100% magnification.
18 seconds rest and another shot. This time ~ 1194 seconds (~20 minutes) long.
Now, you can clearly see a sliver of the amp glow in the D50 image. D80 surprises again. The colour of the amp glow is much more intense however, much less of the frame is affected. In fact less than in the two previous, shorter shots!
The next exposure of just ~122 seconds (~2 minutes) was taken immediately after the 20 minutes exposure.
At full size, D50 is amp glow free where D80 clearly shows amp glow in the corners.
I reviewed all of the above frames on my computer at 100% magnification. I didn’t measure the actual brightness but, simply relied on what my eyes were telling me.
What I have noticed (facts):
In all the shots; when visible, amp glow (lets call it AG) of D50 was confined to upper left corner. D80 AG was visible in both upper corners.
D50 can handle much longer exposures without AG getting offending than D80 can.
AG free area measured as % of the frame area is larger on D50 than D80
AG free area measured in number of pixels is larger on D80 than D50 but see note below.
Shot from cold cameras, both can do 4 minutes or so exposure with no noise. From one frame to the next, with no cooling in between, D50 recovers much better than D80 does. A 2 minutes shot after 20 minutes gives virtually AG free image on D50 where D80 gives clearly visible AG.
D80 body and battery heats up much more than D50 does. After the session, D80 got hot where D50 got warm.
Now, from facts to speculations:
Based on the above findings and 1+ year experience with shooting D50 at long exposures, couple months of using D80 and bunch of samples and information from various other sources, the following are my conclusions so far:
Because ventilation, ambient temperature and who knows what other factors, the results obtained by users under various or even seemingly the same conditions may vary substantially.
Shot from cold, both cameras can produce close to 5 minutes amp free images. D50 can go for 15 minutes with negligible AG where D80 image would have to be cropped. With Long Exposure Noise Reduction turned ON D50 could go for as long as you wish with no need for cropping but some lose of detail in the upper left corner. Long Exposure NR on D80 is next to useless (note)– it does not completely remove AG so, the long exposure images still require cropping.
If you want good, very long exposures, minimum hassle, straight out of the camera long exposures, D50 is a clear winner.
If you don’t mind a lot of PPing (note) than D80 wins. For extra long exposures, it may require framing the scene a bit wider to allow for cropping yet, the cropped, AG free area is still going to be of higher resolution than from D50. D80 can be set to take and combine in camera up to 3 exposures so; one could easily set it to stack (say) 3 frames of 3 minutes each and get a resulting, , virtually AG free 9 minutes long exposure straight out of the camera. Cropping can be done right in the D80, if one desires so. Wired remote, illuminated top LCD and larger viewfinder give it handling advantage for night shots. Mirror pre-fire is also of importance to some of the low light shooters. Having said that, I ended up with a number of shots that got ruined by the amp glow. I didn't frame with enough allowance for cropping. The amp glow was stronger than adjustments allowed by the colour control points in Capture NX so, needless to say, I am not happy with D80 long exposure performance and until Nikon fixes the problem I advice that; if you are thinking about ever taking long exposures, you should NOT even think of buying D80!
The "Amp Glow" is not just an amplifier glow. It's possibly caused by uneven heating of the sensor. This may be due to a number of various electronic and electrical components heating up during long exposures. Well, this is what I thought until I shot 4 exposures, 660 seconds long with only 1 second between the exposures so; the sensor could not cool down between the shots and, in theory, should be getting hotter and hotter so, with each subsequent exposure, the amp glow should increase in size and intensity. Now, I am not sure what to think... See for yourself; the frames below are in order of shooting and if you think that maybe I reversed the files, check the EXIF!
Additional facts: With Long Exposure Noise Reduction activated, D80 takes and processes (after the image capture) a dark frame shot that is roughly 1/2 of the length of the initial exposure. D50 and D70 take dark frames of the same length as the initial exposure.
And back to speculation: It appears that, if Nikon increased the duration of the dark frame for the Long Exposure Noise Reduction, it would work better on the amp glow but, it would still not completely remove it - the size of the amp glow in the subsequent dark frame would differ from the actual shot.
If anybody has a good, easy and working solution for processing the images affected by amp glow, I'm all ears!
A side note: Many of the low light / night shooters are also into IR photography. If you are, you should know that out of the box D80 is much less sensitive to IR than D50 is.
A little tidbit that may be of interest if you are into astrophotography: Just like in D50 and D70 / D70s cameras, a median filtering is applied to every image.
Below is a small crop from a shot of LCD display. On the left is an image with filtering applied and on the right an image where filtering was interrupted:
I can only wish that Nikon would allow users to turn off the median filtering. That would make many people very happy!
Notes:
- According to very reliable sources like Thom Hogan, there is a substantial sample variation when it comes to amp glow and D80 cameras. Some, especially early production cameras, may exhibit some amp glow at shutter speeds of 1/8s or even faster. Since my camera shows it only at longer exposures, I should consider myself to be a lucky one! And I thought that getting Nikon was getting quality and reliability not a lottery!
NOTE Read Part 2 about NIKON D80 amp glow at long exposures
Written 15 September 2006
Last edited 27 October Nov. 2007
© Andrew Kalinowski
- Support Andrew's efforts to document Canada's beauty - purchase the maps and software that you need from: www.CanadianMaps.ca or license / purchase photographs from this site - contact Andrew@FotoCanada.ca