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Bildkritik: vanishing points on the run

... and false shadows that are perhaps correct

Wieder einmal hat uns ein DOCMA-Leser ein schönes Beispiel dafür geschickt, wie „Bildbearbeitungs-Profis“ mit Perspektive und Schattenwurf umgehen. Diesmal haben wir beide Arten von Fehlern in einer Montage vereint: falsche Fluchtpunkte und eigenwillige Schlagschatten. Tatsächlich? Doc Baumann zeigt Ihnen auf, was an diesem Bild nicht stimmt … und was vielleicht doch.

Bildkritik: Fluchtpunkte auf der Flucht
Vanishing points: In this case, it requires actually do any detailed analysis. Another picture on the same page shows that the grills were simply replaced with an identical background and do not fit into the scene.

You have to take a closer look to discover the false perspective in this ad for a gas grill. After all, one of the two vanishing points of the device is placed almost right. However, what stands out at first glance, are the crazed shadows.

The direction of illumination of the scene is easy to read against the body shade of objects: For landscapes, trees and house the sun is top left. The two persons acting reasonably consistent, shadow distribution and Shadow fit, this fall at a slight angle to the right. However, one wonders, in this sharp illumination why their density with increasing length decreases so much.

And so also writes submitter Peter Bauer: "Dear Doc Baumann, yesterday I decided spontaneously to buy a gas grill. The choice at the hardware store of my choice was quickly made. Arriving home, the purchase of course had to 'be justified. For this I researched on the side of the manufacturer, I found this in a variety of sources for reviews and so on. At first glance, it seemed strange ... the size of the grill to the people seems to be wrong. So an assembly and not a real picture? Last security gave me then the shadows: why should project the shadows of the unit in an arc from the otherwise straight-running housing shadow of the grill lid when it is opened and the sun is obviously in line with the case? And why run the shadows of the legs under the table in a different direction? This one Link to this site, What do you mean?"

Bildkritik: Fluchtpunkte auf der Flucht
Light times from the left and from the right times - there is wrong but what!

Mysterious Shadow

So let's first look these shadows closer to. The Sun can be determined quite well on the basis of the flowerpot Far left: The direction of the sun is easy to read on Shadow, and it connects its right end with the top of the pot plant, then the height of the sun produces.

So far so good. Let the grill itself first of all taken into account. The shadow of the right flower pot fits well to this lighting situation such as the beams of the house. But what about the observation of our readers: Why the shadow of the chair legs and seats running under the table in a different direction? And not only that: the bar between the windows and doors cast a shadow - and this time to the left, ie in the opposite direction.

I see two options: The first: Because someone has constructed entirely wrong shade. The second: If that's true (and DER or that already has trouble recreating the shadows of the grill half right - then why should anyone bother to create additional unnecessary shadows in a direction other than that which he or she just has used?

No shadow, but light

Meine Vermutung geht daher in eine ganz andere Richtung: Die scheinbaren Schatten der senkrechten Balken des Hauses sind gar keine. Stattdessen entspricht ihre dunklere Farbe einfach jener der Holzdielen, und die hellen Bereiche dazwischen sind … Reflexionen des Sonnenlichts durch die großen Glasscheiben.

It would also explain why the chairs back so strange - and vigorous - are shadows. Which owe to the mirrored through the window sunlight.

Entirely clear, the situation is, however, still can not be, because then it would actually also a pseudo shadow give where the right flower pot interrupts the reflected rays, and one wonders why the table casts no shadow.

Vanishing points at will

Bildkritik: Fluchtpunkte auf der Flucht
Fluchtpunkte: Mit einer solchen Konstruktionszeichnung kommt man der falschen Perspektive auf die Spur – umgekehrt angewendet hilft sie bei eigenen Projekten, derartige Fehler zu vermeiden.

Dass der Grill einmontiert und nicht mitfotografiert ist, ist eindeutig. Dazu bedarf es nicht einmal komplizierter Rekonstruktionen – es reicht, wenn man auf derselben Webseite ein anderes Grill-Modell sieht, dass in die ansonsten völlig unveränderte Szene montiert wurde. (Oder die beiden Models schaffen es, völlig unbewegt zu verharren, bis ein anderer Grill vor ihnen steht – vergleichen Sie dazu das Bild am Ende dieses Beitrags.)

This variation can be excluded, however, because the grill was unique and perspective inserted several times wrong.

You should research the picture above to: The only reliable object edges in this image are the house and the terrace. you pull them along lines of flight (blue), then meet on a level where you would expect to also correct the horizon (green). Even the table and chairs depart therefrom easily; her vanishing point slightly above the horizon.

Building lines along the right edge of the grill (White) converge at least near the horizon, albeit it. It would have to be at his left, oblique frontal side. But these lines of flight (red) meet in a vanishing point far below the horizon (far left), what can not be.

Vanishing points and shadow

Dass nun der Grill einmontiert ist, lässt sich nicht allein an seinen falschen Fluchtpunkten ablesen. Zum einen gibt es fehlende Schatten, denn zum Beispiel die Bedienknöpfe vorn müssten eigentlich Schlagschatten werfen, ebenso die auf der Platte verteilten Lebensmittel.

Secondly, the shadows of the device on the wooden floorboards is quite adventurous. Why about the hood does not cast a shadow, but the right shadow edge is completely smooth? And where does the strange hook on the underside shadow?

Incidentally, of course, also subject Shadow perspective, and so would have the right shadow edge having a steeper angle. What amazingly, almost true is its distance from the object. (The can easily be determined by connecting to a new level, the top of the round bush left with the end of his drop shadow with a line and then move it as far to the right until its left end touches the right edge of the grill. Construct then another line in the direction of the drop shadow - where the two meet, ending this).

Learned something again!

As you can see, is also reflected in this example again a lot for their own practice to learn. The poor image editor / inside can say with some justification, of course: What should I, if I get given a background scene and to barbecue photos to fit either from the perspective, nor from the lighting? (In Photoshop CC you can at least turn a little at the prospect of such three-dimensional objects.)

But we also learn that you have to be careful with criticism and could be something right sometimes that looks completely wrong at first glance.

Bildkritik: Fluchtpunkte auf der Flucht
Vanishing points: In this case, it requires actually do any detailed analysis. Another picture on the same page shows that the grills were simply replaced with an identical background and do not fit into the scene.

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Hans Baumann

Doc Baumann is primarily concerned with installations (and their critics) and with the unmasking of image forgeries, also with digital graphic and pictorial techniques. In the media again and again as "Photoshop Pope" dubbed dedicated since 1984 to the digital imaging and writes since 1988 about it.

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  1. Der “Haken” am Schatten gehört zu einer Aufnahme mit geschlossenem Deckel. Und dass der Grill perspektivisch nicht ganz korrekt eingefügt wurde, möge man dem armen Fotografen nachsehen. Ich weiss aus eigener Erfahrung dass es saushwer ist, Objekt so zu fotografieren, dass sie später perfekt in ein anderes Foto integriert werden können. Im übrigen empfinde ich die Montage, trotz der zu Tage geförderten Macken, als weitgehend harmonisch und damit “konsumierbar”.

    1. Der Fotograf kann ja nichts dazu, soferm er nicht genau weiß, wie die fertige Szene aussehen soll. Und der Monteur ist ebenso wenig schuld, wenn er nur solches Ausgangsmaterial geliefert kriegt (obwohl man, wie erwähnt, mit Photoshop CC die Perspektive solcher Obkelte durchaus ein wenig korrgieren kann). Wenn man nicht wissen kann, welche perspektivischen Bedingungen das andere Foto haben wird, in das integriert werden soll, ist es nicht nur sauschwer, sondern unmöglich, das zu berücksichtigen. Wenn man es allerdings weiß, kann man die Bilder schon aufeinander abstimmen – man muss lediglich dafür sorgen, dass die Horizonthöhe übereinstimmt (und natürlich ebenso die Beleuchtung). DocB

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