I'm sure there is a very good reason why the longer focal length lenses have longer hoods. Why?

Thx

-- john bosso (jbee193@aol.com), May 25, 2002

Answers

The ideal lens hood would block all light from hitting/entering the front of the lens, except that light which is actually image forming. Hence you notice wide angle lens hoods are square, or better yet the fancy curves given to them by some manufacturers (Canon for instance, and others..). On the tele side, the angle of view is much smaller, and the lens hood can be made longer, indeed must be made longer, to effectively block all but the image forming light from entering the lens.

That being said, manufacturers, Leitz included, nearly always skimp on the hoods for some reason. Maybe in their "testing" they discovered that a skimpy hood is nearly as good as the perfect hood. I dunno. I'm of the school that the hood must fit the angle of view and format of the film. Hence on the Hasselblad, not only the compendium lens shade, but masks for the longer lenses like the 250mm. Using the 250mm and Zeiss Mutar there is even a smaller mask.. you'd think how in earth does the light get into the lens, but the size is correct for the small angle of view involved.

Hope that helps!

-- Charles (cbarcellona@telocity.com), May 25, 2002.

I like to make my own hoods by buying ones intended for longer lenses and selectively sawing them off until they aren't in the way. The results can often be quite long, relative to what the manufacturer built. My favorite stupid hood is the one on the 25mm Voigtlander-- put a filter on the lens and it immediately and obviously eclipses the field of the useless little ring they call a "hood" (but not the field of view of the lens, however).

-- Michael Darnton (mdarnton@hotmail.com), May 25, 2002.

... and the worst light is that that comes in from the side and bounces around off the interior of the lens barrel or "skips" off of the surfaces of the elements. At a certain point the hood is deep enough to block most of this type of light unless you are photographing the sun. Hence manufacturers (like Leica) will design a hood that works on more than one lens of reasonably similar focal length; such as the older hoods for the 35/50 'Crons and the 90/135TE's.

;-),

-- Jack Flesher (jbflesher@msn.com), May 25, 2002.

John - hoods should be as long as possible to shade the lens as much as possible. Long is good.

The IDEAL lens hood (actually available for some large-format view cameras, also Hasselblad) is a bellows with a solid front that has a rectangular/square hole cut out to just barely clear the edges of the lens' viewing area - so that NO light that's not actually part of the picture gets to the lens. I think someone made a version for 35mm cameras, but it ended up being bigger than the camera/lens, so it's never sold very well.

The hoods for normal and wide lenses have to be cut further and further back as the angle of view increases. Basically below about 35mm they are essentially useless for shade, since they have to be SO cut back that a lot of extraneous light still hits the front element.

-- Andy Piper (apidens@denver.infi.net), May 25, 2002.

Andy, not so on the wides.... you _can_ effectively shade the wide lenses such that no non-image forming light enters the lens, but remember... when the the lens is that wide, there's a lot of light thats going to be image forming! An example is the 38Biogon Superwide. The bellows shade works perfectly for this, and you can, by looking thru the lens thru the back of the camera (at the corner of the frame, adjust it just a hair beyond its marked position on the shade, and get essentially full protection, and no cutoff from the shade.

-- Charles (cbarcellona@telocity.com), May 25, 2002.

I have a custom made lens shade for a novoflex 105 macro lens that is a tube 5-6 inches long, and I was amazed to find no cutoff with it. This just to demonstrate that the "goal" would be a hood the blocked everything **except** exactly the angle of view. The angle of view actually decreases with closer focussing (the effective lens focal length increases), so a fixed size relationship between any lens and a matched hood could only be optimal for "infinity", which is why these guys are talking about the compendium/bellows type hoods. If you are in the studio, and have huge light sources of several feet, you have to be pretty good at blocking light. Modern and Leica lenses do flare, but not usually to a crippling degree.

-- l smith (lacsm@bellsouth.net), May 25, 2002.

As an afterthought.... take a look at the hoods used on 35mm cine camera lenses. OMG, talk about hoods!

-- Charles (cbarcellona@telocity.com), May 25, 2002.

I realize the most of the people who write describe themselves as prefering handheld photography. But when using a camera on a tripod outdoors, you can often use your body as a lens shade. This can really help with wide angle lenses. You just stand in such a was as to block the sun, ensuring that no light hits the lens directly. Fire the camera with a cable release or self timer.

-- Jim Lennon (jim@jmlennon.com), May 25, 2002.

To follow up on Jim's point - even hand-held you can often find something to block a specific light source (like standing where a tree trunk blocks the sun). In the studio these source-specific shades are called 'gobos'. I use a lot of naturally-occuring gobos - trees, buildings, people - if they happen to be in the right spot.

Charles - with regard to the effectiveness of wide-angle shades, you're right. I was refering to most manufacturer's shades, including Leica's, which just aren't worth bothering with AS SHADES - they just don't block much more light than the filter ring itself - but may give some physical protection.

The bellows-type shade will work with any focal length in any format if adjusted correctly, but is still not perfect. If the sun (or other light source) is very close to the picture edge, it will STILL be throwing some light on the bottom edge of the front element even if the shade 'crops' right to the edge of the field of view - and that light will cause some flare.

-- Andy Piper (apidens@denver.infi.net), May 25, 2002.