Category Archives: Tips

The importance of exposure and colour balance

The recent viral photo of a dress of controversial colour demonstrates that the perception of colour is a complex psychovisual phenomenon that involves not just the physical electrical impulses produced by the light receptors in the retina but also interpretation by the brain based on context and expectation. It also underscores the importance of getting your exposure and whitebalance correct.

Philosophers have used colour in debates about the notion of “qualia“, or the “the ways things seem to us“. From a photographic perspective, we can understand how a dress which under normal lighting looks to be royal blue with black lace can look in the photo to many people as being white with gold lace. There are two issues with the disputed photo that contribute to the confusion, it is badly exposed and the auto white balance is extreme.

I assume that the photo was taken by a phone and that the autoexposure was fooled by the darkness of the dress. The photo was consequently overexposed leading the royal blue parts of the dress being rendered a much lighter shade of blue. The dark lace parts of the dress are also brightened and now longer looks black.

The second issue is that the camera then tries to colour correct the image by setting a white balance. It misinterprets the scene as being taken under high colour temperatures, e.g. at dusk with the illumination of a clear blue sky. To compensate, it changes the colours in the scene, effectively trying to make the blue dress look more white as it assumes that this is “actual” colour of the dress. To bring blue closer to white, the camera adds yellow to the scene (you can tell from the yellow colour cast to the background). The dark lace of the dress, already made a lighter shade by the overexposure, is now given this yellow colour cast which can be interpreted as being a golden colour, especially in the context of the rest of the dress which is rendered as palish blue.

These two effects combine with the way the brain tries to work out what the colour of objects are from visual stimuli. Since our vision has to operate under many different types of lighting, what we perceive as colour of an object is not actually the actual colour cone responses, but what our brain retrodicts based on our assumptions about the lighting. An apple under noon day lighting will look different compared with viewing at dusk, but we don’t usually say that the apple has changed colour because our brain will take the different lighting conditions into account and interpret that the apple is the same colour. The case of the dress is simply a case of the camera being fooled together with the way our vision system operates.

Tripod Technique

Previously, I discussed selecting a tripod and head. A tripod opens up a whole new vista of photographic possibilities but to make the most of the stability of a tripod, proper technique is needed.

Stability and Mounting

The first consideration is making sure you’re not overloading your tripod legs and head. The heavier your equipment and the narrower the angle of view (more zoom), the more sensitive will the final picture be to residual vibrations and external forces such as wind. I seldom shoot at focal lengths greater than 200mm so my tripod needs are comparatively simple. If you have 300mm or longer zooms, a large sturdy tripod with a gimbal mount is recommended.

If your tripod does not have a quick release, you’ll be screwing your camera directly onto the mounting plate of the tripod head. One thing to watch out for is that if you take a photo in portrait format, the camera can twist and unscrew itself. You may find this happening if you tilt the camera to the left (so that the handgrip is to the top). By rotating the camera so that the handgrip is to the bottom, then the torque of a heavy lens will tighten the mounting screw instead and preventing further rotation.

If you find yourself having to mount and dismount your camera from the tripod repeatedly, a quick release plate might be a good investment. It’s increasing rare to find tripod heads without them in any case. The de facto standard mounting solution is the Arca-Swiss plate which has a dovetail and a matching clamp. Do note that some variation exists between nominally compatible plates and mounts from different manufacturers. There are many other types of quick-release mechanisms to suit cameras of different sizes and applications.

You should avoid raising the centre column of the tripod if possible as this makes the whole system more flexible. For the same reasons, you should spread the tripod legs out to give a wide base.

 Shutter Release

The main priority of using a tripod is stability, whether for long exposures, or simply to get rid of hand shake. To reduce the possibility of introducing vibration when activating the camera, you can use a remote shutter release. The traditional mechanical remote release is a plunger attached to a sheath and cable screwed into the shutter. This was superseded by electronic wired remotes which allowed functions such as an intervalometer and times long exposures (minutes to hours). Wireless remotes (usually IR) are becoming popular nowadays. Any of these will prevent extraneous vibration due to touching the camera when starting the exposure.

If you find yourself without a remote release, your camera may have a shutter delay function, usually 2 or 10 seconds. The 10 second delay is to allow you to get into the shot, the 2 second delay is so that after pressing the shutter release, the camera and tripod has time to settle before the actual exposure. If you do not need to trigger the shutter at an exact time, then a 2 second delay can often work as well as a remote release.

Even if you use a remote release or camera timer, there are other sources of vibration that could impact upon sharpness. In an SLR, the mirror has to be raised out of the beam path before the shutter activates. This raising of the mirror can lead to vibrations. Some DLRs have a mirror-lockup function that allows the vibrations due to the mirror being raised to dampen. It is often combined with the 2s timer delay. “Mirror-slap” will usually have greatest effect at an low to intermediate shutter speed, a critical range of exposures where mirror-lockup gives greatest benefit.

Even on non-SLR cameras, the shutter actuation can cause vibration. The opening of the front-curtain can cause blur. Some cameras have “electronic first curtain” (EFC) where the physical first shutter curtain is replaced by an electronic means of starting the exposure. This eliminates any vibration at the start of the exposure.

Miscellaneous

Sometimes the ground itself can vibrate, e.g. bridges. In this situation, it will be difficult to achieve sharp results during long exposures. You may want to time your exposures in between passing cars or pedestrians. On some surfaces, the distortion caused by your own shifting weight can cause the tripod to move during long exposures.

One thing to watch out for is image stabilization, either lens or camera based. Some image stabilization systems do have modes specifically for tripod use but often you’ll get better results if stabilization is switched off when mounted on a tripod.

Getting it right in the head

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Long exposure of Singapore skyline

In my last post, I spoke of the importance of getting a good tripod. Many people skimp  on their tripod and consequently do not get the best use out of them. Most importantly, a light and compact tripod will be more likely to be on hand when you need it. It’s a case of any tripod is better than none.

I mentioned another oft neglected item and that was the tripod head. It connects the camera to the legs and should be sufficiently adjustable yet still rigid. One thing to remember is that the load ratings of heads are to be taken with a very large grain of salt. There is no standardised way of specifying the acceptable load that a head can handle. It is actually the torque that a camera+lens exerts on a head that most needs to be resisted.

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PHD-41Q pan and tilt head. The horizontal arm controls the roll, the other controls both pan and tilt. Built-in spirit levels keep everything straight. A large quick release plate completes the package.

There are two main types of head, pan and tilt heads (panheads) and ballheads. Panheads have two or three separate axes of adjustment, pan, tilt, and roll (video panheads will omit the last). There will usually be three different knobs or handles, one to control each movement. Sophisticated versions will have geared mechanisms allowing fine adjustment of each axis. In contrast, a ballhead will use a single locking mechanism to control the motion of a ball and socket joint allowing all three axes to be adjusted simultaneously. A separate pan  movement is also usually added to the base of the ballhead. The advantages of a ballhead is that it is often much quicker to adjust. They are often smaller than a comparably rated panhead.

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Centre: Benro B-0 + QR plate and 1/4″-3/8″ screw adapter. Clockwise from top left: Novoflex Ball 30, Manfrotto 494, FLM CB-24, Gitzo G075.

For panoramic use, the footprint of the head becomes crucial. Looking down from the viewpoint of the camera rotating around the no-parallax-point, often you’ll have the baseplate and various knobs taking up valuable area in the nadir region. It can be tricky to find the right ballhead which minimizes the nadir hole. My current favourites are the Novoflex Ball 30, FLM CB-24, and Manfrotto 494 (with the friction knob removed). The 494 allows the locking knob to be adjusted so that it can point down in the locked position, useful for reducing the nadir footprint. The same can be achieved on the Ball 30 by unscrewing the knob and reattaching it in the right position.

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FLM CB38FT with Power Quick Release. This uses very small quick release plates on the camera

To reduce my equipment load, I have dispensed with quick release (QR) plates. These simply add bulk, especially if I need to attach the camera to both the panohead or the tripod ballhead so requiring extra plates and locking mechanisms. I find it takes little time to screw on the camera or panohead. Unfortunately, it is increasingly difficult to find higher end heads without a quick release system. It may be a fashion trend since having Arca-Swiss plates on everything looks “more professional”.

A good ballhead will be secure when locked down. It should be rigid so that vibration is minimised. For large and heavy lenses, these should be mounted to the head rather than the camera. For the extreme telephoto lenses, a gimbal mount may be warranted. These place the rotation point near the centre of gravity of the camera lens, reducing the torque and giving a more stable platform.

Note that there are two commonly used screw sizes used to attach tripods, heads, and cameras. These are 1/4″ and 3/8″ screw sizes. Most camera tripod sockets will be 1/4″, but tripod screws can be either. You can get adapters between the two screw sizes, it is usually not a problem to adapt a 1/4″ male screw to a 3/8″ female socket, but the reverse adapter is quite bulky.

In Praise of Tripods

A tripod is essential for photographs like these. RX100M2 and the crappiest tripod, as stable as a Jenga tower. But I was still able to get the shot with a bit of care.
A tripod is essential for photographs like these. Shot with a RX100M2 and the crappiest tripod, as stable as a Jenga tower. But with care I was still able to get the shot.

They are the most under-appreciated component of your kit. You may pay hundreds or thousands of pounds to get the latest high resolution camera or lens, but the simplest and most cost-effective way of obtaining the sharpest photos is to get a good tripod and use it.

First of all, bring a tripod with you if you can. Obviously, a tripod is useless for street photography but for many other activities, a tripod becomes practical. For some types of shot, such as night photography (left), it is essential.

Get the best you can afford. There is no perfect tripod, but there are plenty of terrible ones. A tripod needs to be sufficient for the equipment you are going to mount upon it. It also needs to be light and compact enough so that you will take it with you. Unfortunately, this usually means that the third variable, cost, is the one to suffer. But the old adage, “buy cheap, buy twice”, applies especially to tripods.

Depending on what you shoot, you may require several tripods. I have a large sturdy tripod which never leaves the building where my office is. I use it for product shots, groups, and self-portraits. For general travel, I have a Benro C-169M8 Travel Angel carbon fibre tripod similar to this. It is for me the right balance of compactness (39cm folded), lightness (1.3kg), and sturdiness (8kg max. load) for doing panoramas and long-exposure photography. If I need an even more compact tripod, I have a Sirui T-1205x tripod which shaves a few hundred grams and a few centimetres in length. I also bought a Benro Traveller Flat C1190T as I was intrigued by the way it folded flat. It occasionally gets used when I have to pack it in a tight space where a conventional tripod would be too thick.

Attack of the Tripods
L-R: Sirui T-1205X, Manfrotto 444, Gitzo G1028MkII

I still have and use a Gitzo G1028MkII Mountaineer tripod which I bought about a decade ago. Compared to more recent tripods, it’s still very light and packs down with the centre column reversed (without having to bend the legs 180 degrees). The rotating leg locks are a bit fiddly and it’s not quite as sturdy as the Benro and Sirui tripods but with care it can still provide sharp panos. If I had the budget, I’d look at getting a GK1580TQR5.

If carbon fibre is beyond your budget, another option for a compact but still acceptably sturdy tripod is Velbon. Their Ultra Luxi or Rexi range pack down quite nicely and have a quick leg un/locking mechanism. The Luxi comes in L and M sizes, I found the M to be reasonably high. The Ultra Maxi tripods unfortunately do not allow you to swap the head restricting you to the included panhead. The Rexi comes without a head, whilst the Luxi panhead can be replaced, something I advise if you want a more compact setup, the standard one is quite large and heavy.

My tripod selection is skewed towards wide angle and shot teleprime lens use. If you use longer, heavier lenses, then you may need to look at large and heavier tripods to get the required stability. One has to also remember an equally important part of your tripod and that is the head. I’ll address that in a later post. I shall also cover tripod technique.

So you’re shooting your first wedding…

If you’re serious about photography and your friends and family consider you handy with a camera, at some point you’ll be asked, “Can you shoot our wedding?” Here’s my point of view, having been in this situation as a relative/friend with a camera way too often.

First point of advice: Run away! You get the occasional cowboy but your working professional wedding photographer actually earns their keep and I have the utmost respect for what they do day-in, day-out. It’s not just about having expensive cameras, even more expensive lenses, or fancy software, what you should be getting when hiring a pro is years of experience handling a high pressure situation and getting the shots when it matters. You don’t get many second chances at weddings and considering how important the photos are to how it will be remembered, the couple should think carefully of not ascribing the appropriate budget to photography, especially considering the total cost of the wedding.

If possible, convince them to hire a professional photographer, one with experience and with a good track record, especially in being able to produce photos in the style preferred by the bride and groom. Just as a marriage requires matching the right people, it is important to get a photographer who will be appropriate for the occasion. The primary photographer should be responsible for the “money shots”, the ones which are the bread and butter of any photo album. Have the couple draw up a list of shots which they would like, especially the group photos which can be endless in their permutational possibilities. Having a trusted friend of the couple (usually the Best Man) handle the logistics of the group shots is one way of reducing your workload to simply taking care of the photos instead of herd management. The last thing you want to have to worry about is where is Aunt Murtle or nephew Johnny? It’s easier if there is someone familiar with friends and family who can go chasing up on errant guests.

Try to enjoy yourself and let the primary shooter get the primary shots, you do what you can to fill in the gaps. If I can get out of being the primary photog for friends, I usually end up doing street photo/candid shots to give a more informal behind the scenes sort of document to the day. When you don’t have the pressure of being first shooter, you can try for the more artistic or risky shots, most of them will fail but you could end up capturing their favourite shot of the day. This may require getting in close to the other guests, or hang back and observing. It depends on the situation and you have to be adaptable. I find that a wide angle lens and being in the thick of the action is a good way of getting fun and intimate shots.

Even as second shooter, I usually have two bodies to reduce lens swapping. One with a 70-200mm telephoto zoom, the other with a 16-50mm standard zoom. I’ll also have a 35mm/1.8 and 50mm/1.4 large aperture primes for low light situations. It is important to anticipate what camera/lens is required at any given moment and to have it ready. For the official ceremony, you should have a good idea of the sequence of events and what shots are needed. Rehearse following the bride down the aisle and the route when leaving the ceremony. Scout the areas where you will do the formal portraits and groups shots. During the more relaxed and informal moments, you have to keep a good lookout for photo opportunities. Kids are invariably cute, especially all dressed up for the occasion.

Preparation will make things run a lot smoother. Planning the day, where you have to be and when, what equipment is needed for which shots, and even the little things like where to park and how to get all your stuff safely to where it needs to be. A checklist can help prevent you forgetting vital tasks.

It is tempting to use your camera as a machine gun, shooting anything that moves. Afterwards you’ll regret having to go through thousands of images. Certainly take those extra safety shots for the ones which matter (groups shots, formals, portraits), but you should try to be selective about the other shots, making sure that each frame counts. It’ll reduce the amount of backing up, editing, and processing you’ll need to do. There’s no harm in keeping shots varied, just don’t get too focussed on repeated shots of the same subject.

Post wedding, you will need to sort, edit and produce a contact sheet for the couple to have a look at. Even at this stage, you should be ruthless in pruning extraneous shots. Couples always have a tendency of wanting even more shots, magnifying your workload. Particularly if you are doing a wedding as a favour or for reduced rates, you want to restrict the amount of unnecessary effort you have to expend. You need to be strict in the number of agreed final photos to deliver. The final output will determine the degree of post-processing required. A set of 6″x4″ prints to put into an album will require only cursory white-balance, levels and curves. Large portrait prints may require a visit to Photoshop to get rid of blemishes, sweat stains (not a task I relish, especially having to manually touch up a hundred or so photos), to smooth skin,  and generally make each shot look its best.

Samyang 8mm/2.8 on the NEX-7

CornerFix requires a reference shot in order to calculate a lens profile. This should be an shot of an evenly lit neutral surface. For a fisheye lens, this proves problematic as you cannot simply point it at a neutral grey card or white wall. I set up two flashes either side of the camera. I held up a white diffusion sheet so that it wrapped around the lens and gave full coverage over the angle of view (180 degrees diagonal). I then took several shots making sure that the image was not overexposed (no clipping).
Magenta lens cast in the corners due to oblique rays causing non-uniform response
CornerFix is able to compensate for the non-uniform response and reduce the colour casts

I just received my copy of the Samyang 8mm/2.8 fisheye in native NEX mount. I’ve tried it on the NEX-7 and have some very preliminary remarks. First the good news, it’s sharp, light, compact, pretty well made, and matches the form factor of the NEX-7 quite well. The only downside so far is the interaction of the lens with the sensor leading to magenta corners.

This lens colour cast is due to the way that off axis light rays interact with the filter stack on top of the sensor and the pixels themselves. The different coloured sites in the Bayer array are affected differently leading to colour casts. This can be a problem with certain lens designs where the exit pupil is situated close to the sensor (non-telecentricity).

To fix this, you can use CornerFix, a program which takes DNG files and applies a rescaling to the data to compensate for the lens colour cast. One has to first create a reference file from which the compensation can be calculated, not exactly straight forward for a 180 degree diagonal fisheye. I have made such a correction profile and people can download the file (you may need to right mouse click and choose “save link as”, or similar). The lens was set at f/5.6 but the profile should work more or less at other apertures. The correction isn’t perfect, but for most photographic scenery it corrects the majority of the colour cast, as well as the vignetting (which can be adjusted).

Photoworld Talk Addendum

Thanks to all who attended the Edinburgh Photoworld. I hope that people were able to get  something out of my talk. I took a pano at the start of the day (left). The full pano can be seen here. More of my panoramas can be found here.

I have had requests for the links I gave at the end of my talk. Here are some links below, it’s by no means exhaustive, but hopefully they will be able to get you started.

I also run panorama photography courses for medium and advanced photographers. Please contact me if you are interested in attending a session. Small group tuition is also available.

Hardware

  • Nodal Ninja. Recommended manufacturers of panoramic heads.
  • Agnos. Italian manufacturer of panoramic heads.
  • Red-door. UK reseller of panoramic equipment.
  • 360 Tactical VR. Local reseller of panoramic equipment.

Software

  • Hugin. Open source free software for assembling panoramas. (multi-platform)
  • wiki.panotools.org. Information source for panoramic photography.
  • PTGui. Commercial pano software (PC).
  • PTAssembler. Commercial pano software (PC)
  • Calico. Commercial pano software (Mac)

 Viewing

  • Panozona. Open source, free software for constructing VR Tours
  • DevalVR. Free (non-open) local viewer
  • Gigapan. Share gigapixel panos.
  • HD View. Microsoft technology for displaying high resolution panoramas.
  • Zoomify. Software for zoomable display.

General Information

Fake Battery?

The battery on the NEX-7 is quite small, 1080mAh at 7.2V. With the EV, LCD and LiveView, this means that a spare battery or three is essential. I went onto Amazon to look for genuine spare NP-FW50 batteries and one seller was offering them at less than half the price of the typical seller. If something sounds too good to be true, it probably is. When I received the battery, the packaging looked authentic, hologram and all, but the battery itself looked subtly different from the one I got with the camera.

The major differences I can spot are:

  • The battery casing is different, the suspect one does not have the grooves behind the label
  • The printing is different, crisper on the genuine one, e.g. the QR code
  • There is text missing on the suspect battery, “2ICP9/30/39” which appears on the genuine one
  • The engraving on the bottom right is different
  • The shape of the connectors on the top right is different
  • The colour of the top right corner is a different shade of cyan

I’m trying to get confirmation from Sony whether the battery from Amazon is genuine or not. So far, the battery is working. It charges up and displays percentage charge remaining on the camera. I’m not familiar enough with the run time of the genuine battery to tell whether the Amazon battery has the same amount of juice. The issue however is that I could have just bought for even less money a non-fake third-party spare battery which would have performed just as well.