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Lens Hoods and the Digital Sensor


ian_white2

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There are many lists on the web showing the compatibility of lens

hoods and various lenses when used on 35mm cameras, however I have not

found anything useful for use on Nikon digital cameras (other than

hoods for DX lesnses).

 

The narrower angle of view should allow a smaller and less obtrusive

hood, and at the same time remove extraneous light.

 

Does anyone know of such a list or can they share their successes in

this area?

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<i>The narrower angle of view should allow a smaller and less obtrusive hood, and at the same time remove extraneous light.</i>

<p>

I'm not sure I'm following your logic here. Hoods are used to prevent flare caused by stray light from sources outside the frame striking the front element. Having a smaller sensor doesn't change anything. As suggested above, a deeper hood could actually be used, and would be more effective. However, there's no reason I can see to believe that small sensors let you get away with a shallower one.

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Paul,

 

your answer is very confusing. Sorry.

 

The isssue is the angle of the lens shade cone, so can you rewrite your comment to reflect that, please. And then the poster might get your otherwise flip idea. [What does "larger lens shade" really mean for you here? Did you per chance mean "narrower and longer"? Because "larger" is indeed wrong ... ]

 

And incidentally, I have not seen (Nikon, get to work on it!) any list or Nikon list numbers of lens shades for use with a 50/1.8 or 300/4 on a 1.5 crop factor Nikon DSLR. Are they manufactured by Nikon? Anyone else?

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Yes, in principle what you are saying is correct. I use 52mm filters and hood for a lens with 58mm filter thread when using the lens on my D70. This varies from lens to lens (angle of coverage and the construction of the lens). There is NO list anywhere to be found and you have to make your own as you go along. Experiment.
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On the other hand, now that I think about it, it might be possible on a DX camera to use a hood that is narrower and shorter, blocking the same angle as seen from the front element, and so reducing flare to the same degree, yet being more compact. But I don't really want to do the math on that.
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Absolutely this is correct. Sensor size does matter. Think about it: all lense create circular images. We record rectangular or square images. So-called "perfect" hoods crop the image area to the rectangular area that we record (plus a little area to prevent mechanical vignetting). Round hoods cut the circle down to just larger than the film size. 35mm-format lenses could and should have different hoods when used for digital photography with sub-24x36mm sensors.
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Last year I posted this image comparing the 17-55mm/f2.8 AF-S DX (left), 17-35mm/f2.8 AF-S (center) and the 24mm/f2.8 AF-D (right). See the hood for the 17-55 DX (front left) is much larger than the one for the 17-35mm, even though their widest settings are both 17mm.

<P>

<CENTER>

<IMG SRC="http://www.photo.net/bboard/image?bboard_upload_id=20004684">

</CENTER>

<P>

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Frank,

Sorry for my not perfect english, I ment a deeper lens hood. I think Ocean Physics explained quite well what I was saying. On top of that the photo from Shun Cheung gives us the proof.

 

I will try to explain. The lens hood is there to prevent (not usable) light to enter the glass. When we have a smaller sensor (film) size the angle field is smaller when using the same lens. Therefore we could use a much deeper (longer, larger) lens hood to keep unwanted light out, while not blocking the image on the sensor.

 

When unwanted light enters the glass we could get glare due to reflections between the different elements of the lens.

 

Ian,

Is this what you where talking about?

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Frank, Vivek, and Jim understand the issue. The others are not there yet (and I don't mean this to be a criticismm I am just looking for info).

 

The issue is the angle of the lens shade cone(in Frank's words). I have uploaded a picture which hopefully is easier to understand.

 

The standard hood for 35mm with the 28-105 is the HB-18, better suited as a dog food dish. When used on a D70, I can use the much more elegant HN-23 and still get no vignetting. Which would you rather use?

 

Simple trigonometry (Ocean Physics can check this out) tells me that the angle between the circumference of the hood and the center of the objective lens is 121 degrees for the HB-18 and 96 degrees for the HN-23.<div>00DsZF-26098784.jpg.8563e429b7b2d4c197aad9c1b306e57b.jpg</div>

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I took the HS-11 lens hood for the 50mm f/1.8 and put it on my 24mm f/2.8 wide angle (the two lenses have the same diameter). The HS-11 is considerably deeper than the hood sold for the 24mm. I took a few shots of a brightly lit white wall and didn't see any vignetting. Interesting. It makes sense that a deeper hood would work, as several previous posters have explained. It's night here now but tomorrow I'll take a few shots of the sky and check them more carefully. Right now I'm feeling a bit foolish for having bothered to buy the "recommended" hood for the 24mm.

 

Chris

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The lack of information on this subject is appalling, in fact this discussion is the only place I could find on the net that brings it up...

 

Anyway, I'm thinking that in many cases the field-of-view conversion factor that is used for lenses could be applied to lens hoods as well, as long as corresponding lenses exist in the line-up and have the same filter thread. E.g. if "digital turns my 24mm into a 36mm lens" why shouldn't I be able to replace the hood for my 24mm f/2.8 (HN-1) with the one for my 35mm f/1.4 (HN-3)? Both lenses have 52mm filter threads. I realise that other factors will play a role as well, like entry pupil, how deeply the front element is recessed into the barrel, etc. But one a whole, it might give a good starting point for experimentation.

 

I shall give it a try once my eagerly awaited first digital SLR has arrived...

 

Cheers

Steffen

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