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  1. #1

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    Lens Hood for 45mm A lens for P645N

    I have the above camera but no lens hood. It seem that the Pentax hood for it is the RH-RA 70mm screw-in( the lens filter thread is 67mm so I am not clear why it is a 70mm hood) but I cannot locate such a hood. Anyone any ideas where such a hood might be obtained and at what cost? Ideally as I am based in the U.K. a U.K. or European source would keep postage costs down but I may have no choice in the matter

    Alternatively what do other P645N owners use for the 45mm A f2.8 lens? It doesn't have to be a genuine Pentax hood as long as it fits the lens and accepts a filter as well

    Thanks

    pentaxuser

  2. #2
    phirehouse's Avatar
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    http://www.amazon.com/s/ref=nb_sb_ss...mm%2Caps%2C303

    Some examples of simple aftermarket type hoods which should work for you.

  3. #3

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    According to my Pentax 645 SMC lens manual, the correct hood for the 45/2.8 is the RH-B70mm, which is described as a "slide over" type of hood rather than a screw-in. That explains the 70mm diameter. It is the only slide over type of hood mentioned in the hood chart of my manual. The others are the RH-A58mm (75/2.8, LS75/2.8, LS135/4) RH-B58mm (55/2.8), MH-RA67mm (120/4 macro), RH-A77mm (80-160/4.5), and RH-RB77mm (35/3.5) Of course, the 150/3.5, 200/4, 300/4 and 600/5.6 all have built in hoods. This manual pre-dates the WA zoom so it is not mentioned.
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  4. #4

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    Quote Originally Posted by revdocjim View Post
    According to my Pentax 645 SMC lens manual, the correct hood for the 45/2.8 is the RH-B70mm, which is described as a "slide over" type of hood rather than a screw-in. That explains the 70mm diameter. .
    I checked with the Pentax Forums site to see if I had made a mistake but it clearly says that the hood type is RH-RA 70mm screw-in and in fact there is no place on the A lens(manual) for a slide-over hood The FA(autofocus) has a slide over hood type PH-RBC 67 bayonet but while I understand your reasoning why a slide-over might be 2mm more it is still called a 67 which is the lens diameter.

    It is a puzzle why if the screw-in fits a 67mm lens it should be referred to as 70mm when the screw-ins for other sizes such as the 75mm lens with a filter size of 58mm are referred to as 58

    It might simply be that the Pentax forum has wrongly used the word 70 when it should have said RH-RA 67mm screw-in.

    So the correct hood for the A lens is clearly a screw-in but the 70mm remains a puzzle.


    Thanks to the other poster for referring me to the 67mm hood on Amazon of which there is a collection. The key here is getting the right type for the 45mm lens which in 35mm terms is a wide angle of about 28mm and might need the petal type of hood.

    The question is which kind of petal hood would prevent vignetting with a filter?

    I know there are quite a few P645 users here and hopefully they might chip in with comments

    Thanks all so far

    pentaxuser

  5. #5
    adelorenzo's Avatar
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    Here is the page from the A lens manual, it is apparently a "cover on" type and not a screw-on.
    Attached Thumbnails Attached Thumbnails pentax.png  

  6. #6

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    It would seem that the Pentax Forums site is a bit mixed up. As adelorenzo has shown, the information given by Pentax is as I described it. Here is the same page from my manual, which happens to be in Japanese.
    Click image for larger version. 

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    As for the suggestion that there is no place on the lens for a slide on (cover on) hood, I don't see why not. There is a large flat area that could easily accommodate such a hood as you can see in the photo below.
    Click image for larger version. 

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    A quick Google search for the RH-B70mm hood led me to this photo.
    Click image for larger version. 

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    Last edited by revdocjim; 05-05-2013 at 03:03 AM. Click to view previous post history.
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  7. #7

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    Thanks for the info. To what on the lens does the "cover on" hood fit to stay in place? Is it simply a friction fit over the lens?I assume that the reference to the thread inside the hood is in fact a thread for a 70mm filter hence the 70mm in the hood's title?

    However if the hood simply slides on the cover then presumably a 67mm filter could be used screwed in to the lens thread itself prior to fitting the hood? The drawback with this would be the necessity to pull off the hood everytime you wanted to change filters whereas with the 70mm thread internal to the hood you can change the filter without removal of the hood?

    Have I got this correct? Thanks

    pentaxuser

  8. #8

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    It would seem that pentax changed the hood for this lens. According to my official leaflet, the correct hood for the Pentax 645 A 2.8/45mm lens is the RH-RA 67mm screw-in rubber hood, although this contradicts the info above. This information is based on a Pentax 645 Interchangeable Lenses folder dated November 1995, just before the release of the 645N; see the attached picture (sorry for its poor quality).
    Click image for larger version. 

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  9. #9

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    Well now it is all starting to make sense. Pentax changed the hood for this lens mid-course. The slide on hood is simply a friction fit, although I believe there may be some sort of indent on the inner side of the hood collar that helps keep it in place but I'm not sure.

    Troll's more recent manual shows the availability of a 67mm screw-in hood. Given the choice I would probably favor that one.

    Perhaps this is why the Pentax Forum was confused.
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  10. #10

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    It certainly sounds as if the changed hood means that if you want to change the filter or add a filter you have to remove the hood. If this is the case then with a wide angle 45mm lens a non Pentax petal type might be best rather than the Pentax round rubber hood and a lot cheaper as well.

    I have no experience of petal hoods but while it seems that the large petals are positioned at the sides and the smaller petals at top and bottom, it is possible with a locking ring type of petal hood to move the petals to another position if the sun's position dictates this so that type of petal hood has advantages.

    However as I said, I have never used a petal hood so I am interested in other P645 user's experiences or I suppose other 645 camera users' experience as I presume that the same considerations apply with any 45mm lens on any 645 camera

    Thanks

    pentaxuser

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