Category Archives: Technical

First rule of Pano Club…

Lens entrance pupil
The image of the aperture stop of a lens when looking from the object side is the entrance pupil. Light rays that can pass through the lens to form an image must pass through the entrance pupil, hence this defines the point of perspective. To avoid parallax when rotating the camera, it must be rotated around the entrance pupil

From Wikipedia:

“The geometric location of the entrance pupil is the vertex of the camera’s angle of view[1] and consequently its center of perspectiveperspective pointview pointprojection centre[2] or no-parallax point.[3] This point is important in panoramic photography, because the camera must be rotated around it in order to avoid parallax errors in the final, stitched panorama.[4][5] Panoramic photographers often incorrectly refer to the entrance pupil as a nodal point, which is a different concept.”

Repeat after me, “It’s not the nodal point, it’s not the nodal point, it’s not the nodal point!”

Simple Hugin Example with “Wrong Technique”

Sunset over St Andrews Harbour, Scotland. Equirectangular projection 360 deg x 180 deg. Sony A7m3 + Samyang 12mm/2.8 Fisheye, Nodal Ninja 3 Mk III, Capture One, Hugin, and Picture Windows Pro. This is the final stitch without adjustments. Further post-processing steps may include exposures curves, sharpening, saturation adjustment, and eliminating dust spots in the sky.

Source Images & Hugin project file (17MB zip)

Creative Commons Licence
This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.

Here is an example of a simple 360 deg panorama in Hugin that shows that good results can be obtained using “wrong” techniques. Specifically, you can use autoexposure, even for highly contrasty scenes that normally would required bracketed exposures and HDR+Tonemapping.

For post-processing, you can crank up the highlight and shadow recovery and individually tweak each frame for exposure. It is not necessary to shoot with manual exposure with each frame with the same exposure settings, nor process them identically.

Additionally, you do not need very much overlap between frames in many cases, only a few control points can do, and they only need to be placed along the seam lines.  A few manually well placed control points can quickly give a good stitch.

This example also shows some other things that you may need to watch out for. You should clean your lens and sensor. I’ve not been able to do much photography lately so my equipment has not been maintained as well as they should have been. My lens also needs to be adjusted as the plane of focus is slightly skewed and it does not reach infinity focus. This is slightly masked by the depth of field at f/8 but can still be detected in the full sized source imagery.

I have provided downsized source images and a Hugin project file if you want to have a look at how it was assembled. I only spent a few minutes putting it together so I’m sure it could be further optimised. The final full sized and processed panorama can be seen at 360Cities. I adjusted the exposure curve, sharpened the image, tweaked saturation, and repaired the dust spots in the sky.

First Shot. I set up my tripod with a Nodal Ninja 3 Mk III. The rotation axes of the panohead is aligned with the no-parallax-point of the lens (it’s not called the “Nodal Point”!). I tilt down to minimise the Nadir hole, bringing in the tripod legs slightly also helps reduce the size of the Nadir patch. I oriented the first shot to capture some bystanders, making sure that they were towards the centre of the frame (don’t want to have anyone cut in half). I also made sure to centre the brightest spot in the sky as I will be patching it with a lower exposure shot. The camera was set to its lowest native sensitivity (ISO100 in this case) and I used autoexposure. The lens is manual focus and manual aperture so the camera controls the shutter speed automatically. I set the lens to be at f/8 and the focus was placed at an approximate “hyperfocal” distance. I used a remote shutter release to minimise vibration. I recorded full uncompressed raw files for later processing.
Second Shot. I rotates the camera by 90 deg using the click-stop rotator on the panohead. For simple scenes, where there are no moving objects, the amount of overlap between frames can be minimal. Here, there is only 10 to 15 deg overlap between the horizontally rotated shots. In more complex scenes, where the could be moving people, cars etc., it may be necessary to take shots in many more different directions in order to produce a stitch with not objects cut in half.
Third Shot. I had also set up the shot so that the main object in the scene (this rowboat) was captured in one frame. This minimises the possibility of any stitching errors occurring on this object. Though the panohead has been aligned to the no-parallax-point, slight shifts due to uneven ground, movement of the tripod as it is rotated, etc., could introduce parallax errors especially with close-up objects. Centering such potential problem areas reduces the possibility of parallax errors happening.
Fourth Shot. We see a small amount of overexposured sky on the right. Hopefully this area will be covered by the extra shot that is exposed for the sky highlights. A belt-and-braces approach would be to take extra shots on either side of the brightest sky areas. This was done but I have omitted this from the example as it is not strictly necessary to illustrate the points.
Extra Shot. This shot was taken by pointing the camera directly at the brightest part of the sky and allowing the autoexposure to control the shutter speed and capture the highlights. Alternatively, the other shots could have been bracketed, e.g. +/-3EV and a conventional HDR+Tonemapping process applied. Here, we show that a much faster and simpler process can produce acceptable results without the extra shots and processing. The wide latitude of modern cameras reduces the need for bracketing and raw processors are very good at extracting highlight and shadow detail.
Zenith Shot. This is taken pointed straight up. In order to position it in the final panorama, I have included a few features in the corners than can be used to locate it via control points. As there are no important features in the sky, it is not important to precisely align it with the other images, hence it could be manually positioned in a pinch.
Nadir Shot. I have a Nadir Adapter on the Nodal Ninja 3 Mk III panohead that allows the taking of the straight down shot very easily. It also provides extra vertical rail height to allow the A7m3+12mm/2.8 combo to rotate to Zenith easily.
Masking Source Images. The tripod and corners are masked off first. The corners often suffer darkening due to vignetting, masking them off can improve photometric optimisation and matching. The overexposed sunset sky is also masked off and will be replaced by a separate shot that is exposed for the sky. This was taken by just pointing the camera straight at the brightest point in the scene and allowing the autoexposure to set the shutter speed to capture the highlights. The Zenith and Nadir images are also given a circular crop.
Adding Control Points. Only a few control points (CPs) are required to get a good stitch if the rotation axis is well aligned with the entrance pupil aka no-parallax-point (NPP). Some of the images pairs have 4 CPs, some only 2, and a few have more. It is only necessary to place the CPs long the likely seam lines of the final stitch. Placing CPs away from the seams means that alignment is compromised in the regions where alignment errors are actually visible. A few well chosen CPs will give better results than heaps of widely spread CPs that may have mismatched features. NB: The NPP is often erroneously called the “Nodal Point” but the entrance pupil does not in fact correspond to any of the (several) nodal points of a lens (look them up on Wikipedia). It’s like calling the steering wheel a “tyre”, they are both round and are parts of a car, but they are not the same thing.
Preview Window. This is how the aligned images are placed, green crosses show the location of the control points. The small exposure differences will be eliminated during the stitching and blending process. The panorama is exported at a reduced exposure so that the highlights are not blown out. Exposure range compression can be used to bring back shadow detail. Curves adjustment in post-processing can then equalise the exposure to obtain a pleasing image.

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.


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

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.

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.

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.

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.

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).

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.

New member of the stable

The NEX-7 just came into widespread availability this week. I was walking past a local camera store and saw the advert on the window and couldn’t resist popping in to have a play. It proved too much for me to resist and I eneded up buying the NEX-7+18-55mm kit from a nearby store which had one to actually sell (the first shop only had the display copy).

What finally tipped me over the edge? The compactness of the body compared with the A77 is a great selling point. Even if comparable lenses do not differ that much in size between the two systems (E-mount and Alpha respectively), for the short primes I intend to use, the reduction in the size of the body is significant. The EVF is the same as in the A77 which I find to be very usable in most situations I have encountered. The accessory shoe will be useful in the studio for triggers. The inbuilt flash will be useful for the odd fill-flash now and again. I hope to be able to use manual focus lenses with adapters. I still have to get used to the Tri-Navi interface but first impressions are that it is a massive improvement over the NEX-5 which I have used in the past.

I hope to obtain the Rokinon 8mm/2.8 fisheye so that I have a very portable pano rig which leaves the A77 mounted with the 16-50mm/2.8 or large aperture prime ready for street/candid shots. The NEX-7 is small enough that I can bring it along as a backup without too much extra hassle. An LA-EA1 will allow me to mount my Alpha mount lenses when I don’t need fast AF (or any AF for screwdriver lenses).

Pictures below were taken with the NEX-7 fitted with the LA-EA1+35mm/1.8 DT SAM using peaking and magnified view, ISO3200, converted from RAW in Lightroom 4 Beta.