Camera hood - to use or not to use - that is the question!

[MissionMan]

Really? How does that work then?



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http://photo.stackexchange.com/quest...m-bokeh-effect

Have a look at where the graphic called optical vignetting and then think of a hood in place and how this could impact it. As mentioned, not sure if it's correct. Only reason I knew about this was when I got my 70-200 I was confused about the cats eye bokeh on the edges when wide open and some of the responses seemed to indicate the hood could have an effect. If you think about the shaped bokeh lens hoods you can buy that make heart shapes, diamonds etc then there could be some truth because even when the hood is out of view, it still impacts the bokeh


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[Hamster]

http://photo.stackexchange.com/quest...m-bokeh-effect

Have a look at where the graphic called optical vignetting and then think of a hood in place and how this could impact it. As mentioned, not sure if it's correct. Only reason I knew about this was when I got my 70-200 I was confused about the cats eye bokeh on the edges when wide open and some of the responses seemed to indicate the hood could have an effect. If you think about the shaped bokeh lens hoods you can buy that make heart shapes, diamonds etc then there could be some truth because even when the hood is out of view, it still impacts the bokeh


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Thanks for that, interesting. I read that as the lens hood can cause a problem when it's too long, as the images show from the person who used a 56 mm hood and also extended it. But the correct lens hood looked the same as no lens hood to me. The optical vignetting effect looks to be caused by light from a wide angle passing through a large aperture to give a lens shaped projection through a circle. Again, not a lens hood effect as far as I can see.
My understanding is that the shape of the bokeh is controlled by the shape of the hole the light passes through, hence why more lens blades on a diaphragm gives bokeh that seems rounder, since the straight edges of the hole produced are not as apparent. I've not seen shaped lens hoods for bokeh, are you sure you don't mean the covers that you can put over the end of the lens that have a heart or a diamond shape cut in them? These produce heart or diamond shaped booked because they create a shaped hole for the light to pass through (like a diaphragm).

[MissionMan]

Thanks for that, interesting. I read that as the lens hood can cause a problem when it's too long, as the images show from the person who used a 56 mm hood and also extended it. But the correct lens hood looked the same as no lens hood to me. The optical vignetting effect looks to be caused by light from a wide angle passing through a large aperture to give a lens shaped projection through a circle. Again, not a lens hood effect as far as I can see.
My understanding is that the shape of the bokeh is controlled by the shape of the hole the light passes through, hence why more lens blades on a diaphragm gives bokeh that seems rounder, since the straight edges of the hole produced are not as apparent. I've not seen shaped lens hoods for bokeh, are you sure you don't mean the covers that you can put over the end of the lens that have a heart or a diamond shape cut in them? These produce heart or diamond shaped booked because they create a shaped hole for the light to pass through (like a diaphragm).

Yup. I meant the covers for the front although I've seen them packaged as strap on hoods, but the point was that if you can take a photo where the heart shaped bokeh hood doesn't impact the photo (i.e. you have a rectangular photo which is not cut off) , but impacts the bokeh then it would also seem logic that a hood could have some impact on it even if it is out of frame.

[Hamster]

Yup. I meant the covers for the front although I've seen them packaged as strap on hoods, but the point was that if you can take a photo where the heart shaped bokeh hood doesn't impact the photo (i.e. you have a rectangular photo which is not cut off) , but impacts the bokeh then it would also seem logic that a hood could have some impact on it even if it is out of frame.

Ah, ok. I don't look at it that way To me, the only things that have been shown to affect the bokeh, are things that can directly intercept light on its way to the sensor. So a cover to produce shaped bokeh, a diaphragm or the wrong/extended lens hood on a lens. To me, a correctly sized lens hood is outside of the field of view of the sensor (outside of that upper dotted line in the optical vignetting diagram you referred to) and so cannot affect/distort light or bokeh. It would have be sized as such by the manufacturer would't it?