Lens hoods

[stu78]

I am going to show my ignorance here by asking what lens hoods are for!! I never used one with my old Sigma 70-300 zoom as I didn't want to carry it around with me but my new Canon 400 f5.6 has one built in.
Should I be using it all the time or just in certain situations? Can it drastically affect my shots and if so how exactly? I appreciate that it can protect the lens so I usually use it when walking through bushes or high grass etc.
Sorry for what I am sure is a stupid question but I am just starting out in the world of photography having just got my first DSLR 6 months ago and my first compact 6 months before that!

Stu

[rezMole]

Lens hoods are primarily to help stop flare - stray light coming into the lens at an angle. On overcast days, they probably won't make much difference, but on bright sunny days flare can become a real problem.

Personally, I always left the hood on (except when using a flash, when the length of the hood can sometimes block some of the light from the flash). Hoods offer good protection to the front lens element.

I found this out the other day when my tripod fell over and the camera/lens crashed to the concrete floor. Damage done? A dent in the hood. Without the hood, I'm sure the glass would have suffered.

A further reason is that in the rain, the hood stops the glass being rained on.

[Roy C]

I am going to show my ignorance here by asking what lens hoods are for!! I never used one with my old Sigma 70-300 zoom as I didn't want to carry it around with me but my new Canon 400 f5.6 has one built in.
Should I be using it all the time or just in certain situations? Can it drastically affect my shots and if so how exactly? I appreciate that it can protect the lens so I usually use it when walking through bushes or high grass etc.
Sorry for what I am sure is a stupid question but I am just starting out in the world of photography having just got my first DSLR 6 months ago and my first compact 6 months before that!

Stu
I have the 400mm f5.6 and use the lens hood all the time. I do not use any filters so the hood gives some protection. I do not think I have ever used the lens without the hood being up. It is not as though you have even got to put the hood on the lens as it is built-in.

[Martin Thomas]

Any reason you don't use a filter Roy?

I have the 400mm f5.6 and use the lens hood all the time. I do not use any filters so the hood gives some protection. I do not think I have ever used the lens without the hood being up. It is not as though you have even got to put the hood on the lens as it is built-in.

[Roy C]

Any reason you don't use a filter Roy?
Yep, when I first got the lens Martin I was on the point of returning it because of the poor IQ but then someone suggested that I removed the filter - What a difference it made, I could not believe it.
That was a fairly cheap filter I will admit but since then I have got a Hoya Pro1 digital UV filter. I use this one with my 17-40 f4 lens and it does not seem to have any effect on the Image Quality but when I put it on the 400mm f5.6 it definitely degrades the IQ. I am convinced that these filters effect long lenses a lot more then standard or wide angles lenses.
If you use a filter it cost you nothing to test this theory, Try mounting on a tripod and shooting some stationary object like a washing powder cartoon from, say, around 10 metres both with and without the filter. If you cannot see a difference then all well and good but I suspect you will see a degradation with the filter attached.

[Martin Thomas]

Thanks for the insight Roy. I've always fitted a filter on my lenses from the moment they come out of the box - for protection as much as anything I suppose. I've never considered a decent (daylight) filter would degrade the image significantly but it makes sense as it must have internal refraction and reflect some of the incoming light.

My new 40D arrives tomorrow :D so a perfect opportunity for some static test shots as you recommend.