Shooting the HDR Night Cityscape

For those of you that have read my articles on shooting the natural looking HDR Landscape, forget everything you read…well almost everything… when it comes to Night Cityscapes. They are a totally different animal in shooting and processing.

Setting up to shoot

Before we get to exposures and processing, first lets look at how we should shoot a night cityscape regardless of if we are shooting HDR or not.

The first part of this is, even though we are shooting a “Night” cityscape the best time to shoot one is not at “night” but rather during dusk – the 45 minute period following sunset. During dusk it helps that there is still some light to the sky and may help to separate our subject, the buildings, from the background. It will also allow more light on the buildings so we can see more detail in them that may be lost when we are shooting in total darkness besides the light from building and street lights.

Next, since we know we are shooting with much less light than daylight we know we will need to shoot on a tripod because of longer shutter speeds. Of course we could up our ISO but noise is already a huge problem with night shots we really don’t want to exacerbate it more. So the better choice is a sturdy tripod.

When we shoot any long exposures good tripod practices come into play, but they take on even more importance than maybe even shooting a daytime landscape. When we shoot a textured landscape we may not be aware of very small movements. But now when shooting a cityscape with very small point sources of lights, that movement, will be much more evident in our image. So therefore, while I may not use Mirror lockup in a lot of my landscape shooting, I will use it for night cityscapes.

Keeping with our good practices, this also means using our remote shutter releases or timers and I also like to use AEB – automatic exposure bracketing- because it keeps my hands off the camera that could cause movement in between frames (HDR only).

The last part of shooting will be aperture choice. Since most times we are quite a distance from the cityscape and well past the Hyperfocal distance, depth of field is not much of a problem and that opens us up to other choices than we may use during the day. For this shoot I chose f/8 because it tends to be the sweet spot for my lens’s (Canon 24-105mm L 4.0) sharpness. Tests I did this night at f/16 showed just the slightest softness due to diffraction at that aperture. Because of the distance to subject even f/4 is very usable.

You may end up juggling even wider apertures and changes in ISO if you are doing bracketing since you don’t want to hit the 30 second exposure wall that most cameras have. In other words, if you are shooting 3 Exposure 2ev spacing and your middle exposure is 10 seconds you will have a problem because your +2 exposure should be 40 seconds but it won’t be because your camera stops at 30. So then either open up a stop or up your ISO a stop or more. This is another reason I did not use f/16 because it would mean too high of an ISO to get a correct bracket. Now that we are set to shoot let’s move on to the actual shooting.

The Shoot

The first part that most of us get wrong when shooting a night scene, whether traditional or HDR, is that we overexpose them. For the most part a night shot is a Low-Key image. For those of you unfamiliar with Low Key/ High Key; a low key image will have the majority of its value in the lower register of a histogram. A High Key image, the opposite, most of it’s values are in the upper register (No, High Key is not just shooting on a white background) So for our night image, the luminance values of our image will be mostly in the left third of our histogram to give us an image “as the eye sees”.  But, just as when we shoot a predominately Black or White object, our camera’s meter is fooled and is trying to make it a midtone, it does the same thing when shooting at night and relying only on our meter the exposure will be pushed into the center zone of our histogram.

When shooting the night HDR, this problem gets exacerbated even more. If we are doing a 3 exposure +-2EV exposure, our 0 exposure is already over exposed – in this example- and then on top of that our +2 exposure will be all wrong and way overexposed and lead us to an image that is soft, with loss of detail and additional noise.

Understand that in a night image, besides street and building lights, there is almost no energy in the highlight area and shadow areas are supposed to be black and without detail to look correct “as the eye sees”

If we took out the point source lights in Night images and only saw what they illuminated, we would find that the image is not really that high of dynamic range. But since those sources do exist in a cityscape if we tried to capture the scene in a single image, either we would loose detail in the buildings getting the lights with detail or vice-versa. So while a night shot out in the desert illuminated by only the moon could be done with a single exposure, a night cityscape benefits from HDR, if done correctly.

So now knowing what we do, my suggestion as a starting point is to measure the scene and then under-expose by 2 stops. So we are basically shooting a -4,-2, 0 sequence but it may take some experimentation from there. We want our “Highlights” exposure to really only expose the street lights and we want our “Shadow” exposure to be no brighter than a midtone. In the actual shoot I got my best results at 1 1/3 to 1 2/3 stops under.

Shooting in this manor I got these three images

Manual Exposure, ISO 100, f/8, AEB 2EV, 5 Second, 1.3 Seconds, 20 Seconds

Not quite what we are used to seeing in an HDR bracket and as some of you may note, some of the single images may be acceptable on their own as a night image. But they are just not there for me. The only exposure that gets the Christmas tree right is the highlight exposure, the only exposure that gets the building lights right is the Middle exposure and the only image that gets the building exposures right is the shadow exposure.

Could I have probably processed my way to an acceptable single image? Yes, but I don’t want to. (I’m a spoiled HDR brat)

Speaking of processing lets work on that next

Processing the Night HDR Cityscape – Nik HDR Efex Pro 2

The first thing I did with my 3 exposures was white balance them in LR. This is another thing our camera will get all wrong especially since there may be 2 or more different sources of light in the image. I will say balance them to your tastes since I have very strong opinions about white balance and what we get so wrong in doing white balance but that’s the topic of another article. You really can’t do a bulk white balance adjustment to all the images shot in your shoot since the white balance changes as you go from the early parts of dusk where the majority of the light energy is from skylight, to later in the shoot where the majority of light energy will come from tungsten and low/high pressure sodium lights. Personally I chose a custom K setting of 5000°k during the first part of dusk to offset some blue and then a setting of 3700°k to offset the yellow of the city lights later in the shoot. In this instance the WB picker in LR, I feel, does not render the best results. With that done, on to our HDR processing.

Taking our 3 exposures into Nik HDR Efex Pro 2, we’ll start with alignment and deghosting. This is going to depend a lot on how you shot in the first place. But in this example because I was so careful in the shooting, I actually turned OFF, alignment and deghosting. In the perfect storm you can get a sharper more detailed image with out the software doing anything. But it really depends. You can tell when alignment/deghosting gets it all wrong or your shooting technique gets it all wrong, if you see black centers to your point sources of light or micro-ringing around those lights.

Once we get alignment correct we can merge our images and move on to the tone mapping. As I said at the beginning, forget everything I said when shooting the natural landscape. The first thing you should notice is, just like our camera tries to make everything a midtone, so will our HDR programs. There’s nothing wrong with them, (HDR Programs) it’s just what they do. It’s just knowing how to correct for that.

The first thing is compression, as they say in Brooklyn, forgetaboutit. In the first place for the majority of the image, the dynamic range is not that high so there isn’t much to tame with compression. Use too much compression and you will see an instant graying and dulling to the image and I don’t mean just 0 compression, I mean -100 compression. Your results may vary and they probably will, but just be aware, if you see a problem, you may have a fix here.

The next thing to work on is exposure. For most of the shots that night, I ended up reducing exposure by 50-60 % ! Next, work with the shadow and highlight to reduce or increase as necessary to increase detail and contrast globally. If you find it necessary you may need to use some control point to work on smaller areas without affecting the whole image. Use your judgment.

Structure, yes we all love structure but this is one control we really have to be careful with in a night shot. Sometimes just a little will cause huge amount of haloing around the buildings. The other problem is, like it or not, structure brings out noise especially in a blank sky, if you really need to use it use it with a control point on something you want more detail to but noise will not be as visible because of the texture of the object. For me I turn off structure and instead will use sharpening later in the process.

Saturation; I’m a saturation guy but again it is a control we really have to be careful with because it can cause Bloom around the point source lights. So use it to taste but be careful.

At this point you should be done and if you’re like me you finish the image off in Lightroom or Photoshop.

Processing the Night HDR Cityscape – Photomatix Pro 4

Processing in Photomatix proves to be the same situation as HDREfex Pro 2, I’m doing things Iwould not normally do with my HDRs for a natural look.

Opening the images in Photomtaix, I will use the Alignment and  Auto-Deghosting before the merge. Once Merged and I begin Tone-mapping, I’ll start with a Strength of  75 and a Saturation of 70. Where I really go off my usaal path is with lighting effects, I normally use Natural or Narural + in my processing, this time I will go between Medium and Sureal a  setting I almost never use.

Moving down to White Point I set that to about 0.036%, Black point to 1.55% and a Gamma of 1.20 and that’s all I do before I take the image into final processing

Final Processing – Nik HDR Efex Pro 2

Taking the image into LR, I made some horizon adjustments and lens correction (I prefer to do them post HDR process so as to not interfere possibly with alignment). Taking the image into Photoshop I wanted to remove some noise in the image and turned to Nik Define2.0. There are times I would just paint it to the sky and water in the image to retain the most detail in the buildings but I really had great detail to work with in the entire image.

And the last thing I did was sharpening using, of course, Nik Sharpener 3.0, in this instance I painted it only onto the buildings. The sky and water would not benefit from any sharpening and it would only increase noise.

And here is my final image. How “I” like my night images to look. Of course, as usual, your vision may vary.

 Nik HDR Efex Pro 2

Final Processing – Photomatix Pro 4

I followed the same process of noise reduction and sharpening, Thsi time turning instead to Topaz DeNoise 5 using the Raw-Strong setting and Topaz  Detail 2 (soon to be 3)

This is a link to a med res. of the feature image on the top of the page image, my favorite image from 2 evenings done as a wide-format image and Processed with Nik HDR Efex Pro 2