rocketride Loc: Upstate NY

Then you're using a hood on the 24-105 that is letting enough extraneous light in that you might as well not use a hood on it, especially at the long end of its zoom range.

Architect1776 Loc: In my mind

Perhaps yours but not mine.

imagemeister Loc: mid east Florida

Lenshoods are not just for flare protection - they are also for physical protection of the front element and lens !

Architect1776 Loc: In my mind

:thumbup: :thumbup: :thumbup:

rocketride Loc: Upstate NY

That makes no sense at all. If you're using a hood intended for a wider angle lens (17-40) than the lens you're using it on(24-105), then there is a big area inside where the hood blocks light from, but outside the lens' field of view that extraneous light will enter the lens from. You lose, thank you for playing.

SharpShooter Loc: NorCal

Rocket, so are you saying the wrong hood, if it's smaller than the actual correct hood, is actually completely 100% useless, or just LESS effective than the correct hood?!
I ask that because I can show you 10,000 shots taken in full daylight and in studio and NONE of then exhibit even a hint of flare unless I wanted the flare to be there. Many talk about hoods like if you don't have it on the lens all your shots won't be as good. ;-)
SS

rocketride Loc: Upstate NY

Not 100% useless, but definitely enough less effective than the proper hood that I wouldn't take the chance.



I'm sure that you can. Most modern lenses, including the two in question, have very good antireflection coatings and part of the design process involves suppressing those localized flare images that used to be the trademark, but that tends to leave the 'overall-wash' kind of flare that reduces contrast over the entire area of the image, especially if the light source is a big swath of sky, rather than a localized source like the sun. Once you've let a little extra non-image-carrying light into your picture's shadows you'll never get that contrast back.

Architect1776 Loc: In my mind

Have you ever used the 24-105 Canon lens? If not then you are clueless as to the effectiveness of the hood . It works wonderfully on my personal lens. If others have a problem then it is their failure. So unless you use this lens and prove that the hood is useless keep your uninformed opinion to yourself.

CHOLLY Loc: THE FLORIDA PANHANDLE!

If you place your cursor AFTER the quote then people can read what you have to say in context rather than read your reply first, THEN read the post you are replying to.....

rocketride Loc: Upstate NY

I have been using one for two years, now. I leave it to the others here, if they care to judge for themselves who is the ignorant one. BTW, I am an optical designer by trade. What is your knowledge of optics?

ken32708 Loc: Florida

Looks as though I'm late to answer but there is a rubber lens hood that is able to fold back on itself for wide angle or zoom. It works well on my Canon and seems to be indestructible. I've never been happy with any of the tulip hoods since the sun always seems to come through the open sides where a full round hood doesn't have that problem. Long lenses over 300mm need longer hoods. The hood I bought was on ebay for just a few dollars. Sorry I don't have time to get a picture and send it.

rocketride Loc: Upstate NY

A petal-type hood is theoretically the best solution because it minimizes the amount of area outside of the scene that can project 'flare' (images of the lens' stop superimposed, more or less badly focused, on small parts of the image) or 'veiling glare' (a diffuse wash of light over all or most of the image) onto the sensor (or film). It would, with a fixed focal length lens, be possible to engineer a hood that just barely is not in the optical path on all sides and therefore allows almost no flare or glare to get inside from sources outside the image area.

With a zoom lens, unless there's some kind of mechanism to extend and retract the hood, it has to be designed for the wide end of the zoom range, or there will be vignetting.

Even this is a help.


There are three ways that light can get to the sensor (or film) through the lens. (We're not counting light leaks in the camera body or lens here just light that actually gets through the optics.)

The first is image-forming-light. This is the light that enters the lens at the front, refracts* at each lens surface in turn, and arrives at the sensor, forming the image.

Then there are the other two-- glare and flare-- the light that 'cheats the system' and gets to the sensor without having been properly formed into the image. All this light is superimposed on the image, but does not contribute information to it and usually indeed detracts from it. It's a form of noise, in other words.

Flare manifests itself is when light from a small, bright source (like the sun), within or outside of the field of view, reflects off one of the optical surfaces, goes some way back subject-ward in the lens before bouncing off another surface back towards the sensor. This light is usually not well focused and even if it is, each pair of surfaces will form a differently focused image at a different place in the image

Veiing glare happens the same way, but with diffuse ambient light as the source. Instead of discrete images of the stop, if puts diffuse washes of light across larger portions of, or even the whole, image. This results in an overall loss of image contrast.

Multi-layer coatings hugely reduce the amount of light reflected at each surface, often down to less than 1% per surface (compared to typically >10% per surface for uncoated glass and around 5% for single coated glass surfaces). Many current lens designs would be unworkable without multicoatings. Even with all this, you want to keep as much light from coming into the lens from outside the field of view as you can.


* Or, occasionally reflects or diffracts as intended by the designer in 'mirror' or Canon 'DO' lenses. The majority of lenses only use refraction to form the image, though.

Architect1776 Loc: In my mind

I use lenses not sit in a lab thinking about theory. Sort of like Architecture there are those who theorize in colleges and those of us who actually design. You screw up a design and perhaps a bad photo. So what who cares. I screw up a building and people die and that is national news. buildings are far more complex than a lens could ever hope to be with all the materials, systems, codes and other things to consider.
So no I don't design lenses but could if I wanted to with a program. I actually use lenses and have done so from jungles to the artic, on the ocean or from a plane. Lens hoods do work, they are not worthless, they do shade the front regardless of what you think happens and finally they protect the front element at the least.

Resort at Red Hawk Club House and Restaurants, public lives at stake


Boys and Girls Club ( Childrns Lives at stake)

ken32708 Loc: Florida

Good explanation and thanks, but the second portion of your first paragraph would indicate why a solid hood is more preferable.
Thanks for the effort, much appreciated.

rocketride Loc: Upstate NY

How about some where the camera isn't pointed within about 45 degrees of straight away from the sun? In those, you're using the back of the camera (and maybe your head) as your lens hood.