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Image Descrepancies

On many cultivar pages there are images that do not seem to match each other. The Larger image to the top right is the image we have chosen to best represent the cultivar. No images are uncluded which we believe are wrong. But there are many reasons why correct images appear different. When verifying an identity it is important to understand why these images vary so that you can make a more sophisticated decision.

List of Cultivars where a reference image and more recent image, both valid, but vary. See below for Why!: See here for currently contested images]]

List of Slides From Historic Irisarians Which appear to be mislabeled, despite the good reputation of the photographer.

List of Cultivars where two reference images vary

Reasons why images vary: .

Images may vary because of:

  • Technological reasons
  • Climatic reasons
  • Temporal reasons
  • Situational reasons

Technological reasons: During the 1950s to around 1990 Kodacrome film dominated as the slide film of choice but it always skewed the color toward red. Bluer Irises always appeared more violet then they where. Ectachrome did a better job on blue but the red tones became more lavender. With the advent of digital images digital cameras originally provided striking blues, almost too blue. Modern equipment has greatly improved but it is still possible for settings to be "off". Today we can Photoshop to improve their accuracy. In earlier times only printers could make these changes and catalog pictures may have been adjusted. In the 1800's images were often hand colored. Obviously images using different technologies will vary from each other. Often it is best to take into account all of them when trying to reach a detrmination of identity.

Climatic reasons: Plants respire day and night. Respiration burns sugars which may be important color components. Respiration is slower under cold conitions. Photosynthesis is the opposite of respiration and is regulated by the amount of light. Thus a plant in a desert climate (cold nights and sunny days) will build more sugars like purple anthocyanin. Some cultivars are affected more than others. But for the most sensitive color can be extremely intense in desert environments and very washed out in areas of warm balmy nights and cloudy days. Thus we see significant color changes in some irises from East Coast to West Coast and again overseas. Unfortunately these differemces have not been systematically documented for individual varieties.

Temporal reasons: As Flowers age they can change color. Japanese irises do not expand fully until the second or third day. As they expand the color becomes less concentrated and the flower appears lighter in color.

Situational reasons: Some flowers tend to fade in full sun. Images taken when they first open can look quite different from images taken hours later, while counterparts grown in the shade may retain more color. Soil conditions can effect flower color. Some say that plants grown on acid soils have sharper blues. At this time I know of no studies that verify these speculations or quantify them with any particular cultivars. It seems logical that the availabilty of different chemicals in different soils should cause some changes in color.

All of the above factors can alone or in combination effect the images presented for each cultivar.


-- BobPries - 12 Feb 2019
Topic revision: r19 - 25 Jul 2019, BobPries
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