The photo used in the samples below was taken a week and a half ago on the Washington Coast. The moon was about first quarter and the clouds were really thick so there really wasn’t a lot of light. I wanted to at least get a few images done that night before the moon set so I used ISO 400 and exposed most of the images, including this one, for 15 minutes with Long Exposure Noise Reduction turned ON.

All of the images could have used at least another stop and a half of exposure - the histograms barely breached the 50% mark. My estimates based on a preliminary ISO 6400 exposure should have been better but I think the light was lessening slowly as the moon set which I didn’t account for. While this isn’t a perfect test scenario I decided to use it because it was a real world situation where although I didn’t correctly expose the image I still really like it and it’s certainly an interesting test of the camera’s capabilities.

The image was taken in portrait position but for this test I cropped off the top and bottom (mostly sky and sand). The first image below is a resized version of the image prior to any adjustments to the histogram and the second image is post adjustments (listed below the image).

Original unprocessed image in DPP 3.5 - click white balance, no adjustments to histogram using RAW or RGB settings, sharpness 0, luminance noise reduction 0, color noise reduction 5, resized to 500px wide

Processed image in DPP 3.5 to stretch the histogram to a “better” exposure - click white balance, brightness +2, contrast +4 in RAW, no adjustment in RGB, sharpness 0, luminance noise reduction 0, color noise reduction 5, resized to 500px wide

Here’s the histogram before and after the DPP adjustments. As you can see it’s a significant adjustment and as well all know an adjustment of this size will dramatically increase the noise levels in the image.

[Warning! The numbers you will read next are estimates only and not intended to be exact.] For an image shot originally at ISO 400 and pushed the equivalent of 1.5 to 2 stops it makes the effective ISO somewhere in the 1200-1600 range. Assuming this is in fact the equivalent of a push from 400 to 1600 there will be more noise in this image after adjustments than there would have been if I had correctly exposed the image with a 15 minute exposure at ISO 1600 in the first place.

What I’m really getting at is that this image should be damn noisy!

Not much to see yet so here are 100% crops from the image. The first in each set is a crop from the original image and the second is a crop from the adjusted image. The first set has one additional crop which is the crop of the adjusted image with the Dust & Scratches filter applied (see my last post). Keep in mind that with the exception of the third crop from set one no software based luminance noise reduction has been applied.

Crop 1

Original

Adjusted in DPP

Dust & Scratches

This shows pretty much what I would expect - decent noise levels in the original and increased noise levels in the adjusted image. The Dust & Scratches filter definitely makes a difference in removing some of the speckles and results in an improved image. Overall the noise levels really aren’t bad at all.

Crop 2

Original

Adjusted in DPP

Crop 3

Original

Adjusted in DPP

Very similar results for crops two and three - increased noise levels in the adjusted image but still holding up very well considering the circumstances.

And finally, crops from a screenshot taken at 50% viewing (print size was 40%) which are similar to what you would actually see on a print.

50% crop 1

50% crop 2

I don’t see anything in the 50% crops that would prevent me from getting an excellent print from this image especially considering I have made absolutely no effort at noise reduction or selective sharpening.

So while the 100% crops are moderately (but not unexpectedly) noisy (remember it was a 15 minute exposure at ISO 400 pushed the equivalent of 2 stops!) the 50% crops look great and in my opinion it’s an impressive performance.

[Update] I should add that once the Pandora’s box of noise reduction and sharpening has been opened the results are so wide ranging that it’s probably impossible to definitively conclude what is the “best” result without actually seeing a final print (no one in their right mind would publish a full size image on the web for “final” viewing). Since I published this post I’ve been playing with a variety of noise reduction and sharpening tools/scenarios and while it’s clear this image can be vastly improved it’s hard to say which tools/scenarios yields the “best” results. However, so far I would venture to say that once printed (excluding massive enlargements and assuming a well prepared image and a knowledgeable printer) no one would even mention the noise as an issue.

Gasworks Park, Seattle, WA

This is a photo from behind “The Mound” at Gasworks Park. This was taken a couple nights before the most recent full moon - which despite being the largest full moon of the year was no match for the marine layer of clouds and rain so common this time of year in Seattle.

I’ve also just posted a photography guide for Gasworks Park as part of the Free Photo Guides community project. If you find the guides useful and are willing to contribute be sure to contact me!

I may be the last one to have figured this out but it’s new to me so I’m posting it anyway. It’s really easy to get rid of the “speckly” noise I pointed out in the last couple posts using the Dust & Scratches filter in Photoshop. My testing has showed that it results in no loss of image quality and doesn’t smear details like “normal” noise reduction generally does. It also works considerably better than the Despeckle filter which gives you no control and visibly blurs details.

Here is a 300% zoom crop (it’s visible way below 300% but I just wanted to make it easy to see) before and after the Dust & Scratches filter was applied.

Dust & Scratches filter before and after, 23 minute exposure, ISO 400, Long exposure noise reduction ON, Settings: Amount 1, Threshold 10 (vary the threshold)

An important side note - this is a crop from a 23 minute exposure at ISO 400 taken in succession to three 15 minute exposures at ISO 400. Long exposure noise reduction was ON for all exposures and while the 15 minute exposures showed no speckling the 23 minute exposure did. There was definitely some threshold that was crossed during that extra eight minutes but I’m not sure if it was a result of the longer exposure or that the sensor was finally starting to heat up after more than an hour of exposures with little break in between.

The Dust & Scratches filter also works really well on the long exposure tests I posted earlier where the images without in-camera long exposure noise reduction showed speckling. Here is the 15 minute long exposure without noise reduction before and after the Dust & Scratches filter. I converted to black and white because it was easier to see the difference - in the color version there is still some color blotching left but it is far less noticeable than the speckling.

Dust & Scratches filter before and after, 15 minute exposure, Long exposure noise reduction OFF, Settings: Amount 1, Threshold 6 (vary the threshold)

Clearly the filter makes a significant difference here and until I see otherwise, for me, it’s justifiable to skip long exposure noise reduction with these results. Also for what it’s worth I don’t think this would work for astrophotography for obvious reasons.

Ocean Shores, Washington

Some of you may remember the photos I posted a year ago (wow!) with seagulls taking bread out of a friend’s hand…
http://www.brianchapmanphotography.com/blog/2007/12/16/washington-cost/
http://www.brianchapmanphotography.com/blog/2008/01/24/inquiringmind-focus/

Well this year I was the hand model and the camera was the 5D2. I can tell you this camera is heavy enough that it’s very hard to hold up to your eye over an extended period of time with one hand while the other is outstretched with nearly frozen fingers holding a piece of bread!

If you click through to the flickr site where the image is hosted you can also view the ultra large version with all the details - and there are plenty.

Also an update for anyone wondering about the “black dot” issue - I contacted Canon support and their response was actually quite funny. It seems as though they are aware of the issue and they are “preparing a countermeasure.” In any case, I’m glad it is being worked on and I hope it’s fixed soon.

[LINK TO PART 1]

Well, after taking a weekend trip to the Washington coast, rebuilding my computer Sunday night, and trying to recover some files from a dying microdrive (I only lost two) I am finally able to post part 2 of the long exposure noise tests!

Here are the basic specs from the last post:
- Ambient air temperature was about 70 degrees F
- ISO 100
- f8 for 15 minutes
- Processed with DPP 3.5
- DPP noise reduction and sharpening OFF (sharpening will exaggerate all noise and the type we’re looking at here is no exception)

In this test I’m looking at the difference in a 15 minute exposure when the in-camera long exposure noise reduction (LENR) is ON or OFF. The first crop of each section is with LENR
OFF and the second crop with LENR ON. My comments are at the bottom.

Again, keep in mind that there was no sharpening and no attempt to extract the most detail from the images so evaluate only on how the image holds together over the longer exposures.

Here is the full image - slightly different this time but it makes no difference for the tests.

Crop 1

15 minutes - Long exposure noise reduction OFF

15 minutes - Long exposure noise reduction ON

Crop 2

15 minutes - Long exposure noise reduction OFF

15 minutes - Long exposure noise reduction ON

Crop 3

15 minutes - Long exposure noise reduction OFF

15 minutes - Long exposure noise reduction ON

From these three crops it’s clear that besides the minor (and if you don’t think it’s minor look at the images below before jumping to conclusions) speckling and minor differences in exposure the images are virtually identical. In my opinion these results are amazing.

Below are three other variations of how one might judge the noise in an image.

Extras

15 minutes - Long exposure noise reduction OFF - Bicubic Smooter to 50% size

15 minutes - Long exposure noise reduction ON - Bicubic Smooter to 50% size

15 minutes - Long exposure noise reduction OFF - Screenshot of “View -> Print Size” in Photoshop CS3

It is clear from the additional views including both the down-sampled image and the screenshot of the ‘Print Size’ view that the tiny speckles are only visible if the viewer has their eye against the monitor and really knows what they’re looking for. Needless to say the results are very impressive and have far surpassed by expectations.

More soon…but probably not these “studio” type tests, it’s a little boring…

Brian