The MacKinnon Collection Digitisation | Cased Photographs

History in pictures

The MacKinnon Collection presents a great insight into the rich history of photography. This shows not only in the variety of the nineteenth to early-twentieth century subjects but also in different printing techniques and presentation formats. Among hundreds of photographs you’ll find portraits of Scots at home and abroad, daily life scenes in the Outer Hebrides, cityscapes of old Glasgow and Edinburgh, Scottish businesses, waterfalls and castles among many other subjects. All these moments in time were preserved in the form of albumen and gelatin prints, photogravures, carbon, salt paper and bromoil prints, and presented as individual photographs, albums, postcards and cartes-de-visite, to name a few. 

Especially attractive within the MacKinnon Collection are the cased photographs. These include around 200 daguerreotypes and ambrotypes as well as several tintypes.  

Daguerreotype – a unique photographic image on a distinctive mirror-like silver surface. 

Unknown artist Four Boys Hand-coloured daguerreotype, 1850s

Ambrotype – a photograph on a sheet of glass backed by black varnish or card which turns it into a positive image.

Unknown artist Unidentified Child Hand-coloured ambrotype, about 1850s

Tintype – a photographic image on a thin sheet on iron (not tin!) A black coating is applied to the surface of metal before the image is exposed resulting in a positive.

Unknown artist Unidentified Children Tintype, 1860s-1870s

Just in case 

What makes these works visually attractive is not only the photograph itself, which in this instance is mainly studio-based portraiture, but also the very case in which the photograph is displayed. Most often it was either a small wooden folding case covered with embossed leather, or a union case. The latter one was made from a mixture of wood and shellac pressed into a mould using a thermoplastic process, which resulted in a look similar to bakelite (a type of plastic the old telephones were made of). These often have ornate designs on the outside. The cases are hinged with tape or small brass hinges, lined with velvet and contain a brass mat which separates the cover glass from the photograph.

The outside of a union case
The outside of a leather case
The inside of a leather case, with velvet lining, brass mat and glazing

The purpose of the case is not only to adorn an image, but more importantly, to protect it while handling and storing. This is crucial especially with daguerreotypes because their polished surface will tarnish if it is exposed to air for a prolonged period, resulting in damage to the image. Also, unlike paper photographs, the daguerreotypes surface is very fragile and susceptible to abrasion.

Man in the mirror

Each photographic image, produced on a mirror-like surface of a daguerreotype, is unique and not reproducible as no negative is created during the process. The daguerreotype is also very accurate and sharp if the original photograph was in focus. Well defined lines combined with a silvered copper plate on which the image was fixed give it almost a three-dimensional feel. With ambrotypes that depth was achieved with the thick glass on which the image was created.

Daguerreotypes as well as ambrotypes were often hand coloured to make them look more attractive. It was done either by painting the colours very carefully directly on the plate or applying powdered tint mixed with dry gum and fixing it by breathing on it. That first method was also used to accentuate detail such as jewellery or lace on the sitter’s dress by gilding it.

Gilded detail in a hand-coloured ambrotype, about 1850s

How we photograph a photograph 

As captivating as these objects are to look at, at times they can also be challenging to photograph. We use a high-resolution medium-format camera with a macro lens but there are additional factors that need to be considered when digitising cased photographs.

3D objects

Cased photographs are objects of various size, thickness and material. They were hand-made, and photography of these objects can often highlight their imperfections. This means that they require a different lighting setup than flat artworks such as prints do, and each of them may reflect light in a slightly different way.

The lighting setup for the MacKinnon cased photographs was designed in a way that the photographs and their cases are shown in a clear manner, with minimised shadows (in extra diffused light), yet still as gilded and embossed 3D objects.

Lighting setup for cased photographs at the Scottish National Portrait Gallery studio

To best document the elaborate nature of these objects, each case is photographed as a close-up of the photograph (main view), a full view of the open case, as well as the front and back of the closed case.

Left, main (official) view and right, open case view
Case front. Unknown artist Unidentified Man Hand-coloured daguerreotype, 1840s-1850s
Case back. Unknown artist Unidentified Man Hand-coloured daguerreotype, 1840s-1850s


With daguerreotypes the image on the highly reflective, polished plate will look different depending on the placement of the case in relation to the camera. This happens because the daguerreotype can be viewed as a positive and a negative image – which one we see depends on the angle we look at it. An ambrotype is less reflective because it is created on glass rather than a mirror-like surface, but glazing may still show the reflection of our camera lens. This is because the camera must be placed on the copy stand directly above the case for it to be properly photographed. Both types of cased photographs often contain gilded elements and are framed in shiny brass mats.

A daguerreotype shows as a positive or a negative image depending on the viewing angle

The solution to this problem is a careful placement of the object within the frame when taking a photograph as well as controlling the light. This is done by blocking, reflecting and diffusing the light with various modifiers, the simplest of which may be a piece of black card.


Some cases easily open flat like a book, to 180 degrees, but others are extremely fragile due to their age or the objects history before it came into the collection. When their condition is compromised the cases may not fully open. This means that to show them all in sharp focus, multiple photographs with gradual focus shift need to be taken. The focus movement may vary from a couple of millimetres to just over a centimetre. Once all the sections of the object are photographed, the images are then focus stacked using Photoshop, so that the final image is uniformly sharp.

Focus stacking. For this image to be all in focus, six separate photographs were taken, each with a small section in focus

There is an additional challenge which is beyond the photographers’ control – a natural deterioration process of the object such as silver tarnishing, dust etc. Some of this damage can be reversed or minimised by the conservation team. Also, some light surface dust can be carefully removed with a dust blower before photographing the image. However,  certain flaws will still be present.

Object in a deteriorated condition

It is natural that such deterioration may obscure or otherwise obstruct the clear view of the image preserved in the case. However, the role of the photography team is to present the object in its current condition, in order to support the work of colleagues from the conservation and curatorial departments. Such photographs also show the object as accurately as possible to the online visitors. 

All images © NGS Photography. The MacKinnon Collection. The National Galleries of Scotland and the National Library of Scotland. Jointly acquired with assistance from the National Lottery Heritage Fund, Scottish Government and Art Fund. 


The MacKinnon Collection was acquired jointly with the National Library of Scotland with assistance from National Lottery Heritage FundScottish Government and the Art Fund.

By National Galleries of Scotland Photography Team, 13 June 2022