Fungus on Formica - REVISITED

[Harold Gough]

What hoods do is to black out everything except what's actually being looked at. In a high magnification macro setup, that means a cone.

To be pedantic (who? me?), we are always dealing with a cone and the format selects from the circular cross-section.

Harold

[Planapo]

Macro setups are often bad for flare because the illuminated area is much larger than the subject. --Rik

An interesting concept! Why, then, are landscapes not an absolute flaring nightmare?

Harold

This would have been easy to see:

I think that Rik implies, on good reason, that macro subjects are often overall reflective, and that the light sources we use, are relatively big, too big to confine lighting just to the spot we want to take the picture of. Hence, inevitably, we have to deal with a large illuminated area that often gives the reflexion causing flare.

As far as I know, it´s different with landscapes: Mostly, they are not very reflective, and an artificial light source is relatively small in size compared to the subject.
But imagine a lake as the landscape on a bright, sunny day. Then you have a situation comparable to the oftentimes encountered macro setup Rik was referring to, namely a reflective surface, and the sun as a big, harsh light source. Flare in this landscape photograph would be a problem to deal with, wouldn´t it?!

--Betty

[Harold Gough]

Betty,

Shiny subjects are a specific problem, absent from most of my subjects, whether macro, landscape or something inbetween. This is largely a filtration (polarizer) issue although that deals only with simple situations and not, or only partially, with contorted, shiny surfaces, more a problem in macro than for general photography.

Harold

[rjlittlefield]

Macro setups are often bad for flare because the illuminated area is much larger than the subject.

I figured that phrasing was going to prompt some discussion. Discussion is good.

I think of the problem in terms of a ratio: How much of the light that hits the lens contributes to the image, versus how much can contribute only to flare?

When the angle of view is large, the ratio is large -- quite a bit of the light contributes to the image. As the angle of view gets smaller, the ratio gets smaller -- the total amount of light hitting the lens does not change, but less of it contributes to the image. If the lens has a tendency to flare, the narrow angle of view provides more opportunity for that to be a problem.

In addition to just the angle of view, the method of illumination matters a lot. In macro setups, without a shade, there are often relatively large and very bright areas not far outside the field of view, contributing nothing but flare. In the setup that I linked (HERE), that pingpong ball diffuser does a fine job of illuminating the subject, but the ball itself is very bright and (absent the black paper cone) is completely exposed to the lens. There's probably 10,000 times more light hitting the lens from the pingpong ball than from the subject. In terms of street photography, it's like trying to shoot the shadows under a roof overhang, while the sun shines directly on the lens.

Think about the ratio. It simplifies the problem.

--Rik

[mgoodm3]

I like the whole ratio thought for figuring lens flare.

[Harold Gough]

We really have to define which flare we are talking about.

The main problem in landscapes if the sun directly causing (multiple) bright images of the diaphragm aperture, so beloved of makers of wildlife films for TV.

The concern is this forum is about the more diffuse flare (probably technically incorrect, but it conveys my meaning) from larger areas of bright illumination striking the lens at other than parallel to its main axis. That at such an angle that it does not contribute positively to the image merely adds significantly to internal reflections which dilute the image with noise. Our lines of defence are hoods and coated filters and lenses for what the former does not exclude.

Harold

[Charles Krebs]

Remember it's not only the lens itself that may be prone to cause problems with flare, but the insides of the entire assembly... bellows, tubes, etc. That's another reason why a lens shade can be valuable.
(This is probably just another way of looking at the ratio idea).

With the view camera we use compendium shades. Used to best effect, these are extended to the point just before they start to vignette the image. In order to allow for swings and tilts, view camera lenses "cover" an area (project an image circle) much larger than the film size. Any part of that image circle that does not fall on the film would be light that is just bouncing around inside the camera looking for a way to cause flare. In effect, the shade externally, and effectively "crops" the image circle that can be formed so that only the light that is needed enters the camera.

There is an analogous situation with macro. Often the optics we use are capable of projecting a relatively huge image circle towards the camera when we are only interested in a small region the size of of the sensor or film. (Not the microscope objectives, but this is certainly the case with enlarging lenses, Luminars, Photars and the like). Even if the lens is exemplary in it's own internal flare characteristics, there is still the matter of all the "extra" image light that is entering the system.

In photomacrography, with the short working distances and the need to light a subject positioned so close to the lens it can be tricky to come up with an effective "micro-shade", but it's often worth the effort. It's also worthwhile to check your set-up by removing the camera body and looking into the bellows/tubes (with subject lights in various locations) to see if there are any surfaces that are obviously reflecting the unused image light back towards the camera. The flat reflective surfaces of a digital camera sensor/filter will also reflect some light back toward the lens and other interior surfaces, so even a bright flange or screw-head that is not directly hit by light as it passes through the lens can cause problems. (On occasion you can come across a lens where the shape and surface of "rear" facing lens elements will catch a significant amount of light light reflected off of the sensor and reflect it back at the sensor again... creating noticeable flare. Some lenses that have been designed with digital cameras in mind have had special attention paid to this potential problem).

[Harold Gough]

With the view camera we use compendium shades. Used to best effect, these are extended to the point just before they start to vignette the image.

This highlights a problem with zoom lenses, many of which have a "macro" capability. The hood supplied can cope fully only with the needs of the shortest focal length. I thought I had solved this by purchasing a three-position collapsable rubber hood. However, it vignettes at the widest end and the start of this is not visible in the viewfinder. (Yes, I know, the wonder of digital would show me. ).

Harold