Looking Up and Slowing Down
Normally when I’m somewhere like New York or Chicago my thoughts invariably turn to street photography. There have been so many iconic photographs made on the streets of these great American cities down the years that it is the genre which automatically springs to mind whenever I am there.
However, on my last visit to both cities recently I resolved to pay a little more attention to the amazing architecture. Armed with a wide-angle lens, a tripod and some ND (neutral-density) filters, and inspired by some of the excellent long-exposure photography I have seen recently, I decided to slow things down and try to make some daylight long-exposure photographs. Normally when I make ultra long-exposure images, I do it because it is dawn or dusk, and the light levels just aren’t sufficient for an exposure with a ‘normal’ shutter speed measured in tenths or hundredths of a second. However. I’ve recently been playing with the technique of using ND filters to reduce the light entering the camera to the point where I can make ultra long-exposure photographs with exposures measured in minutes in broad daylight. I have made exposures like this of seascapes before, but I have until recently never tried doing this with architecture or with a cityscape.
For the image above of Chicago’s John Hancock Tower, the unfiltered metered exposure was 1/320 sec. @ f/9 and ISO 100. After applying 16 stops of ND filtration my calculated required exposure duration was around 3½ minutes at f/9 and ISO 100. I then further increased the exposure (more on this later) by lengthening the exposure duration to 4 minutes and opening up the aperture to f/8 giving the final exposure for the image you see above with the ND filters in place.
Although I am new to long-exposure daylight photography, I do regularly use a tripod, so many of the techniques required to shoot this kind of image successfully were already familiar to me. However, I discovered through my experience of shooting long-exposures in New York and Chicago that there were some additional points to remember to make this work successfully when shooting architecture in the way I did here. In case you’re also new to this and you’d like to try something similar, here are some of the things to think about when shooting long-exposure architectural photography:
1. Clouds are your friends. Fast-moving clouds are your best friends.
Forgive me for stating the obvious, but it’s worth noting that there’s not much point making a long-exposure photograph if nothing in the frame is moving – although preferably not the buildings. If the buildings are moving, then either your tripod is not up to the job, or long-exposure photography should be the last thing on your mind right now. In an image like this, there has to be movement in the sky in order for the effect of a very long exposure to be visible. If the sky is a cloudless blue or it is completely overcast, admit defeat, put the tripod away, and go and grab a coffee, shoot something else, or use the time to do some location scouting. A sky with a good mix of fast-moving clouds and blue sky seems to work best in my limited experience as it generates the requisite interesting contrast in the sky. Too much blue and the sky will be boring and featureless; too much cloud cover, and the sky will be similarly bland and boring with no contrast. You need a balance between white cloud and blue sky to give you some interesting streaks of motion-blurred cloud in your frame.
2. You need quality gear.
I am firm believer that having expensive gear is generally not necessary to make great photographs. However, this is one time when quality gear unfortunately really does matter. To make a high-quality long-exposure photograph in a busy city, you will definitely need a sturdy tripod: trucks and lorries thundering past and office workers and joggers pounding the street mere inches from your trembling tripod legs may cause sufficient vibration to kill your image sharpness otherwise. Secondly, you need high-quality ND filters – there is no point having top quality glass on your camera if you’re going to put cheap, nasty, optically flawed filters on the front of your lens, and this is particularly relevant with this kind of photography since long exposures place particular demands on the filter material and manufacturing process. Making a 6- or 10-stop neutral-density filter which transmits light evenly across its surface and uniformly across the visible spectrum of light is apparently not easy, and unfortunately they therefore don’t come cheap. I use a carbon fibre tripod from Gitzo with a Really Right Stuff ballhead which soaks up vibrations, and neutral-density filters from Lee and Hitech. Singh-Ray is another top-quality manufacturer of filters, and they have recently released a 15-stop ‘Mor-Slo’ ND filter which I haven’t tested but which looks interesting.
3. Slow down and explore before setting up.
Once you have identified a building or which seems promising, don’t immediately launch into a frenzy of setting up your tripod. This is not shoot from the hip. The building isn’t going anywhere. There is probably no decisive moment; only – if the clouds and weather are fickle – perhaps a decisive twenty minutes. Walk around the building with your camera in your hand and frame up different compositions to identify whether they really work. Take time to find the best angle. Try different focal lengths. It’s time-consuming setting up the shot with the tripod and other accessories such as filters and shutter-release cables (see below), so make sure you’ve found your optimum location and angle before you break out the tripod and filters.
As photographer Greg Heisler says: “only stick a tripod under your camera AFTER you have decided your frame. Once the tripod is there, you stop moving around, you stop experimenting with possibilities and you’re stuck with a photo that might not be the best one to take.”
These kind of images are quite stark and minimalist, a simple compositional dance between the sky and the building. They need to work together – if you concentrate too much on one and neglect the other the image will fail. Both building and sky need to be interesting.
4. Be thorough and meticulous.
Each exposure is going to take several minutes. It’s a real pain to complete the exposure only to discover you were shooting at ISO 3200, your focus was off or the lens cap was on (you may laugh, but looking through the viewfinder with the lens cap on is visually indistinguishable from looking at the scene through 16-stops of ND filtration. Ahem.) So really take the time to set up methodically and work slowly and systematically through the preparation for each shot to avoid missing something vital. Like the lens cap. Most of us don’t make these kind of long exposures every day, and some of the settings are not ones we habitually use, so lack of familiarity makes it very easy to screw up.
5. Use an external spirit level.
Many cameras these days have some kind of spirit level built in to the display so that you can see whether your horizontals and verticals really are horizontal and vertical. However, for a shot like the one I made here, the camera was on the tripod pointing straight up at the sky with the sensor plane parallel with the ground, and your built-in level is unlikely to cope with that. So invest in a small spirit level something like this one which mounts in the hotshoe of your camera – they generally allow you to level the camera in two axes simultaneously. If you don’t – particularly if you are shooting with a wide-angle lens – you will have some unwanted distortion in the image that may be difficult to correct in post-processing. Added to which, any software correction involves bending the pixels to some degree and therefore degrades the quality of the image. Much better – and quicker – to get it right in camera at the point of image capture.
6. Remove any prophylactic filters.
When I am shooting in dusty or otherwise harsh environments, and also when I am transporting my gear, I normally keep protective clear filters on all my lenses. I use Nikon NC filters; many photographers use skylight filters for the same purpose. I have had three such filters smashed on the front of my lenses; in each case, the lens front element was unmarked, so I am glad that I had the filters on, as it’s much cheaper to replace a filter costing $80 than to repair or replace a lens costing up to $2,500. However, this is one occasion when you don’t need them; so remove them. You already have enough additional glass (or resin) in front of your lens in the form of stacked ND filters. The less additional layers of filtration on your lens, the better the image quality. Architectural photography is exacting, and to look good, the image needs to be technically flawless – or as near to flawless as you can make it.
7. Have your best disarming smile at the ready.
Composing an image like this is also hard work as you physically need to crouch under the tripod to see the LCD screen unless you have a tilting rear screen as fitted to cameras such as the Sony Alpha SLT-A99 or NEX-7. (Nikon and Canon, are you listening?) Be aware that crouching under a tripod in broad daylight outside a large building in a place like Manhattan tends to draw inquisitive looks even from such worldly beings as New Yorkers who are generally unphased by seeing crazy stuff on the street – and also from over-zealous building security guards – so have your best disarming smile at the ready. In the United States, at least, the general rule is, as far as I understand it, that anyone may take photographs of whatever they want when they are in a public place. Absent a specific legal prohibition such as a statute or ordinance, you are legally entitled to take photographs. Property owners may legally prohibit photography on their premises or land but have no right to prohibit others from photographing their property from other locations. Whether you need permission from property owners to take photographs while on their premises depends on the circumstances. In any case, when a property owner – or building security guard – tells you not to take photographs while on the premises, you are legally obliged to honour the request. In practice, therefore, if you are shooting from the pavement (sidewalk) you should be OK, unless you are causing some kind of hazard or obstruction e.g. if there is insufficient space for people to safely pass. If, however, you step on to an area in front of a building which is private property and set up your tripod, as I did a couple of times in NYC, you may be asked to move on. Even if you are on public land and are not obliged to explain or justify yourself to a security guard, it simply doesn’t make sense in my opinion to inflame the situation. While making this shot from the sidewalk, I was asked by the building security guard what I was photographing. Despite being under no obligation to provide him with the information, I courteously explained what I was doing, and he left me alone after that. ‘Disarm through charm’ is a good motto.
8. Checklist for a Long Exposure.
OK, so you’ve identified a great composition with an unobstructed view of the building or buildings. The sky looks great. The security guard is your new best friend. Time to break out the tripod.
When making the shot, I generally work according to the following sequence:
- Place the camera on the tripod and fine-tune the composition I already identified before setting up the tripod. Make sure the tripod is as stable as it can be, and everything is tightened down nicely. If your tripod has a centre column, either remove it, or rack it down to shorten it as much as possible. A tripod with an extended centre column is significantly less stable than a tripod without a centre column, or with the centre column retracted. If your tripod has a hook underneath, hang your camera bag from it for greater downforce and therefore increased stability.
- If your lens has Vibration Reduction/Image Stabilisation, turn it off now. It can actually introduce vibration when using a tripod, as the system attempts to cancel out vibration which is not present.
- Make some test exposures without the ND filters to check what the correct unfiltered exposure is. The problem here is often that the dynamic range of the scene is naturally high: you are pointing the camera skywards, and the building will be much darker than the sky. So you need a base unfiltered exposure which that retains detail both in the sky and also in the buildings. If the contrast in the scene is too high, it may be necessary to make multiple exposures and blend them in post-processing (i.e. long-exposure HDR), as adding a graduated ND filter – assuming you own one – is unlikely to be able to do the job for you here, and you will have enough ND filters in front of your lens already. Fortunately, since the building is not moving, only the exposure of the sky needs to be a long exposure; the exposure for the building can be a regular unfiltered exposure. Using the camera histogram is essential, in conjunction with the ‘blinkies’ (the blinking highlight display showing you areas of blown highlights in your image when reviewing images on the camera in playback mode). Use the technique of ‘exposing to the right’ to maximize detail in the image and minimize noise without blowing out areas of the sky. It will definitely help to shoot images in raw format if your camera offers this option, since you will be able to capture a larger dynamic range of brightness in raw. Bear in mind also that the in-camera histogram and the ‘blinkies’ are both based on an 8-bit JPG file created by the camera from the raw file, not the raw file itself. As such, both may indicate areas of blown highlights which may not actually be blown once you view the raw file during post-processing. Experimenting with your camera to see how much of these putative blown highlights you can recover in post will help you to learn how far you can push the exposure to the right before the highlights are really blown and unrecoverable. Also, if your camera supports it, check the RGB histogram for the individual colour channels (red, green and blue), rather than just checking the histogram for the three colour channels combined. The reason is that the combined-channel histogram represents an average, and it could easily occur that one colour channel is seriously over-exposed while the other two are not. In the case of the sky, it is the blue channel which is likely to blow first.
- Once you have your unfiltered exposure – e.g. 1/250 at f/8 and ISO 100 – use a long-exposure calculator (either a paper chart you can easily find on the Web, or a smart phone app such as ‘LExp’ which makes the job easy) to calculate the correct exposure with the ND filters in place. This is necessary, as the camera will not be able to meter the scene once you have the ND filters in front of the lens – it is way too dark. Ideally, you want a long-exposure somewhere in the range of 4 – 8 minutes. If you have several ND filters – I have a 10-stop, a 6-stop and a 3-stop – you can combine two of them as required to give a shutter speed in this target range. If the clouds are moving fast, an exposure at the shorter end of the range will be sufficient. You may need to make some test exposures to see how long an exposure is required.
- To minimize digital noise, use your camera’s lowest ISO setting e.g. ISO 100. To maximize image sharpness, avoid the extremes of the aperture (f-stop) range. If you shoot with a low f-stop number (large aperture) such as f/2.8 or f/4, you may not have sufficient depth of field to have all or most of the building in acceptably sharp focus – and furthermore some lenses don’t perform so well optically when wide open, or close to wide open. If you use too high an f-stop (small aperture), although your depth of field will be high, the image will suffer from diffraction softness. The aperture you want will depend on the lens and the distance of the camera from the building, but in terms of the lens’s optical performance, somewhere around f/5.6 to f/11 would normally be ideal. A good rule of thumb is that the sharpest aperture of a lens is around two stops closed down from the widest aperture. So if you have an f/4 lens, then the sharpest aperture is typically around f/8.
- Switch on your camera’s long-exposure noise reduction (NR). I don’t bother with in-camera high-ISO noise reduction, as high-ISO noise is in my view best removed in post-processing. However, there is no software that I have yet found which can do a better job than in-camera long-exposure NR. Unfortunately, it doubles the length of your exposure, as it makes a ‘dark frame’ of the same duration which it then subtracts from the normal exposure to cancel out the digital noise. However, this is still much quicker than spending a long time in post spotting your image to clean up all the hot pixels. (I know, as I learned this the hard way.)
- Screw in the cable release for your camera so that you can trip the shutter without needing to physically touch the camera, or set up your wireless trigger. You will need a cable release or trigger which allows you to hold or preferably lock the shutter open for the duration of the exposure. Many triggers also have timers built in and can be set to automatically close the shutter again at the end of the exposure period.
- Once you have calculated the correct long exposure – e.g. 5 minutes at f/9 and ISO 100 – switch the camera into manual-exposure mode, set your aperture to the calculated f-stop and check your ISO is also correctly set. You may need to tweak the f-stop or ISO slightly to bring the shutter speed into the correct range with the ND filters you have at your disposal. Then put the shutter speed on the ‘Bulb’ setting (with most cameras, exposures longer than typically 30 seconds are only possible at the ‘Bulb’ setting).
- At this point, I normally set the focus, switching to manual focus and using the camera’s Live View mode to zooming in to check focus is acceptable over the whole building, adjusting as required. Once focus is set, if you haven’t already done so, switch the lens or camera to manual focus to avoid inadvertently changing the focus.
- If your camera supports it, switch to ‘Mirror Up’ shutter release mode. In this mode, the first press of the shutter (or shutter cable release) simply moves the SLR mirror up and out of the way. The second press actually opens the shutter. This minimizes vibration caused by mirror movement at the beginning of the exposure and maximizes image sharpness.
- If you can close the eyepiece of the camera, do so now. Many cameras have a built-in sliding cover for the eyepiece to prevent light leaking into the camera through the eyepiece during long exposures. If your camera does not have this, carefully place a hat or a cloth over the top and back of the camera to do the same job.
- Now carefully mount your ND filter or filters in front of the lens, being careful not to move the camera and change the composition or knock the lens and change the focal length or focus. Carefully check the filters to make sure they are light-tight around the edges. Long-exposure ND filters usually have a rubber or foam gasket around the edge to prevent light leakage which can spoil the image. I use the Lee system filter holder which works both with my Lee Big Stopper filter and also my Hitech Pro IRND filters. It’s easy to put the filters in skewed, only to notice this at the end of the exposure after wondering why the image is grossly overexposed.
- Finally, make the exposure!
9. Other Points to Remember.
If you really get in to this style of photography, and find yourself regularly shooting with the camera pointing up at the sky, crouching under the camera all day is going to get tiring pretty quickly. In that case, you might like to consider using a field monitor for your camera.
You need luck with the cloud. Setting up takes a long time so make several exposures if you are not sure you’ve nailed the shot.
It may help to keep a blower brush handy. Because the camera is pointing directly – or almost directly – up at the sky, it is very susceptible to dust settling on the front filter during the exposure. If you are using a fairly small aperture, this may show up in your image. Check the front filter occasionally during the exposure and blow off any significant dust with the blower brush.
Even though you have hopefully ‘exposed to the right’ to maximize the amount of data you captured and minimize noise, you may find that you still need to add additional exposure time to correctly expose the image. I am not entirely sure why this is, although I have read that other photographers frequently experience the same thing. The exposure typically needs to be lengthened by 30-50% to expose the image correctly, as if the sensor is susceptible to some kind of ‘digital reciprocity failure’.
All long-exposure ND filters seem to introduce some kind of colour cast into the image. My Lee filter adds some warmth, whereas the Hitech filters – which block the light at the infrared end of the spectrum – tend to add a cooler blue cast. Either way the cast is easily removed in post-processing so it’s no big deal provided that you shoot in raw. If you shoot in JPEG the white balance is ‘baked in’ to the JPG file and correcting any colour cast is much more difficult.
I hope that you have found the above useful – if there’s anything you want to know about making these images that I haven’t covered, drop me a line in the comments below and I’ll do my best to help. For a larger view of any of the above images, just click on the image.
This final image is not a long exposure, but I saw the Chrysler Building reflected in the glass façade of one of the buildings opposite, and thought it looked amazing…