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The need for a lens hood.

Mike-P
Posted 05/08/2014 - 15:38 Link
johnriley wrote:
I'm not the only one who interpreted your post in another way Mike!

Mmmm, that doesn't surprise me either.
Blythman
Posted 05/08/2014 - 15:58 Link
Mike-P wrote:
johnriley wrote:
Yes, but we're talking Pentax here, not Canon. It is true to say that, apart from a few low cost lenses, Pentax lenses are generally supplied with a hood.

The post was actually just to show that Pentax are quite good in that respect as they provide hoods with even their cheapest lenses. Canon on the other hand charge for anything they can get away with.

But never mind.

I'm surely not the only one who knew what you meant
Alan


PPG
Flickr
cbrog
Posted 05/08/2014 - 16:01 Link
johnriley wrote:
cbrog wrote:
Quote:
Also of course with the APS-C sensors a 1.5 times longer lens hood can be used.

Why?


Roger

Because the field of view is narrower as only the centre of an imaginary film frame is used. So the Pentax 50mm snap on lens hood can be used quite happily on the 35mm DA lens. They both have the same field of view, therefore need the same amount of shading.

Oops! another senior moment John

Roger
MrB
Posted 05/08/2014 - 19:19 Link
McGregNi wrote:
I always use hoods, just seems like common sense .. sure, it won't always make a difference , but it reduces one potential cause of contrast reduction. Lets not forget also the clear advantage of the physical protection offered to the front glass by hoods - on my Samyang the rather short petal hood has saved it from scratches a few times because the front element is bulbous and it is very easy to forget to protect it when moving around.

I agree with you on all points there Nigel, as I suggested in my previous post.

It just so happens that I was in Maidenhead last Sunday, taking a few shots around the road bridge over the Thames. The lens was the SMC Pentax-F 28mm (~25 years old?) with a Kenko MC UV filter, but I forgot to take a lens hood. This shot was towards the sun after 4 p.m. - not sure if it's flare (it does look like it, e.g. on the bridge under the nearest lamp), or my error in exposure, or probably a mixture of both (resampled JPEG OOC):

Comment Image


However, it does not seem to be a serious problem - this is the same JPEG after a few tweaks in PaintShop Pro:

Comment Image


I should have remembered the hood though.

Cheers.
Philip
McGregNi
Posted 05/08/2014 - 21:20 Link
Its amazing what a bit of processing can do for contrast issues now Philip, and clearly it has worked there. I guess the better you start from at the capture stage the better you get at the end though.
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johnriley
Posted 05/08/2014 - 21:25 Link
I found the SMC Pentax-DA 70mm f/2.4 Limited was quite prone to flare and the hood made a dramatic difference.

Many other designs don't seem at all prone to flare.
Best regards, John
drobbia
Posted 05/08/2014 - 22:13 Link
One for the books - Attended a seminar given by a professional National Geographic Photographer - I asked "besides flare,why use a Lens hood?" he said - The sensor in camera is square, the lens is round. a square hood "helps square " the incoming light. --- was he joking or any technical back up for his answer? - tg
johnriley wrote:
The dedicated lens hoods are tailored to each lens and offer the best protection, and yes, always use a hood. Your pictures also show why I ditched routinely using filters a long time ago.

Modern coatings are superb, but lenses have many more elements, so there's still potentially a fair bit of scattered light around.

"It's not what you look at that's important, it's what you see" - Thoreau
Quote:

johnriley
Posted 05/08/2014 - 23:53 Link
Except the sensor isn't square....but then neither is the hood. Petal shaped hoods are the most efficient and we can test this with the 12-24mm hood. When I first got this lens the hood wasn't clicked totally into position and sure enough I got vignetting. It was utterly precise. When clicked fully home, no vignetting.

A squared off hood (longer in one dimension than the other)is also quite efficient, following the dimensions of the film gate.

Round hoods tend to be quite long tubes, for telephoto lenses.

As for the man from National Geographic, I don't know what he was saying.
Best regards, John
K10D
Posted 06/08/2014 - 00:07 Link
I always fit a lens hood if the lens has one supplied or is available as an after market item.

Best regards
Inspiration is rarer than a plate glass camera.....
Dave-L
Posted 10/08/2014 - 02:10 Link
Horst wrote:

Ah, I forgot my Pentax FA 50mm f2.8, A 50mm f2.8 and 100mm f2.8 macro lenses dis not come with a lens hood, because the lens elements are so far back in the body, that the body acts as a lens hood.

The SMC Pentax-D FA 100mm F2.8 Macro WR does come with a lens hood, I have one and it certainly makes a difference for the better, Pentax seem belatedly to have realised this.

Only my 10-17mm fisheye doesn't have one, things can be a bit tricky outside with that one!
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Edited by Dave-L: 10/08/2014 - 02:13
Horst
Posted 10/08/2014 - 02:28 Link
So it does, and of course most or all of the latest Pentax lenses do.

The earlier Macro lenses did not come with a lens hood, because I suppose Pentax thought there was no need for it, because the lens elements where very far set back.
However this was completely nullified when using a filter.
Suddenly there was a glass surface right on front of the objective and exposed to all the cross and other rays.

AN extra lens hood was then needed.

All in all: A lens hood never does any harm, It can only improve the picture quality.

Regards, Horst
gwing
Posted 14/08/2014 - 12:16 Link
I've got quite a few old Pentax lenses without lens hoods - except for the one on my head or the one at the end of my arm
Posted 15/08/2014 - 15:36 Link
Is a hood less important on a very wide lens? eg the hood on my tamron 10-24.
cedricd
Posted 17/08/2014 - 20:25 Link
Reason no.2. Protection for the front element! I inadvertantly dropped a K30 with a brand new 18 - 270. The lens hood took the impact, cracked and sprung away but the lens and camera are fine. Without the hood the railway ballast sized stones would have had a negative effect on the front glass. Superglue and an elastic band and the hood is fine.
Enjoy life

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