When does a hood help?

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Daneinbalto

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Tried to find in-depth info on this but couldn't, so maybe the forum can help:

When is a hood useful in relation to the direction/quality of the light? For example, I understand that a hood will reduce flare if I am outside with a bright sun somewhere in front of the film plane. But what if what if my source of illumination is coming from straight behind me? Will the hood make a difference? What about overcast days, etc.
 
Perhaps surprisingly, hoods are extremely useful on overcast days or in diffuse lighting, because they reduce veiling flare and increase contrast. I used to see this illustrated regularly in the 1970s when I worked at Plough Studios in London, which had one of the few 'infinity coves' of the period. With a white paint-out, lighting could be VERY diffuse, and those who disregarded our advice to use a hood lost a lot of contrast.

Of course, glancing light that strikes the front glass, or bright lights just outside the image area, also make efficient hoods extremely useful.

The main reason you can't find 'in-depth info' on this is that hoods are so useful that it's more a question of finding reasons/excuses for not using them (usually bulk or expense, or with rangefinders, viewfinder blocking), rather than reasons for using them.

Also, a lot depends on the lens design and the aperture used. Fast lenses used wide open without hoods are inviting veiling flare as well as internal reflections.

EDIT: And as Bill says below, they're also invaluable as mechanical protection against knocks, dings, sticky fingers, rain, spraying champagne...

Tashi delek,

R.
 
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From a flare reduction perspective you got it. Overcast days are unique that while you do not have a small strong source of light it still can help.

I like hoods on all the time as they help protect the front element.

B2
 
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To illustrate (sorry without sharing my photo) how it can be a problem... I had photographed a building at a winery years ago with the sun going down behind me, but still a nice blue sky. I may have used a wider aperture because I was hand-holding (Nikkor 35-80mm, one of cheapest lenses they made but not a dud). I never noticed until I printed this image years later that there was a subtle vignetting in the blue sky. It was a problem and I had spend a lot of time photoshopping to get rid to print that promo. Working with a tripod may and stopping down would have helped I believe. I never really understood all those lens tests before, saying "vignetting gone by f/8" or some such thing. It's not a vignetting like a Holga they're talking about. I'm not positive if a hood will eliminate vignetting in that situation, but anyway just thought I'd share the story. Unfortunately I was trespassing and had to hop right over a fence to get that shot, so I did it hand-held but not fast enough. This big guy came by in a pick-up and tried to scare me by waving a pistol around. He succeeded I guess, but hey I'm alive and still using that promo piece!
 
Think of it this way.

Farmers use bill caps to keep sun out of their eyes, use a hood for the same reasons.

Hasselblad, many years ago, said that good hood (as in the Compendium or bellows shade) was as good as multi-coating. They probably sing a different tune these days, but a good, well-made shade is a definite help almost any time. With a hood, you know you have protection, w/o a hood, it is a crap shoot.
 
If your lens isn't coated, or if it has haze or a lot of scratches, you really do need to use a hood if you're shooting in bright light or there's a bright light source in the frame.
 
Double Negative said:
Whenever there's light in the scene. ;)
Click to expand...

When the light is in the scene, it's gonna cause flair hood or not. When the light source (be it a bulb, the sun, or even a bright sky) that is outside the image, using a hood will cut down on the 'stray light' entering the lens. That is the primary function of a hood. The best hoods look like bellows - you can adjust them so ONLY light from the image can get to the lens. The more extraneous light a hood lets in, the less efficient it is at reducing contrast robbing flare.
 
I'm the original poster. Just to clarify, I was not looking for an excuse for not using a hood. Just trying to understand what it does and does not do.
 
It keeps light from outside the picture area from hitting the glass, where it would bounce around between the glass surfaces and end up flattening the contrast. It reduces the chance of getting a greasy fingerprint on the lens. It reduces the chance of smashing the glass into the corner of a table or the like. It gets you to spend a lot more money if you insist on a genuine Leitz/Leica hood. Mostly, though, it's to keep stray light from striking the lens.
 
Hoods have nothing to do with prevention of vignetting. Hoods help stray light from entering into the lens barrel and bouncing around in there, causing rainbows, flaring, ghosting, and all sorts of things that lower contrast. Hoods always help, except when you intend to have lens flare.
 
Just use the hood! It may not be much help on some shots and be major help on others. Are you going to make the hood/no hood decision for each shot? Some of mine have been on the lenses for years!
 
For obvious reasons, rectangular hoods are more effective than round ones. My SLR lenses all came with round hoods. For each hood I had made a push-on "cap" with a rectangle of the correct size cut out. This can be done with RF lenses, though not so easily. Of course it is pointless with lenses that rotate when focussed. If the inside and the edges are not painted flat black there can be trouble.
 
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