Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
01-03-2014, 04:50 PM   #1
Senior Member
zekewhipper's Avatar

Join Date: Dec 2010
Photos: Albums
Posts: 298
Lens Hood Size

I got an 18-55mm f3.5-5.6 WR zoom for Christmas. It of course has a twist on petal hood which I won't use as I detest that type.

For all my other lenses I use nice metal screw on hoods. When I got my 50-200mm, determining the overall size (not thread mount size, but the front end opening), was simple as the supplied hood was solid. All I had to do was measure the end diameter, and then buy a step up ring to bridge the gap between the lens and the hood's diameters. That worked like a charm for that zoom.

However, since the new hood is a petal type, that tells me that simply measuring the end diameter will not do, as the hood already is technically too small for it or else it would not be petal shaped. Does anyone have any idea of just how large the open end diameter of a solid hood should be so that you don't have vignetting at 18mm?

I already have determined that it will need to be greater than 72mm.

01-03-2014, 05:03 PM   #2
Administrator
Site Webmaster
Adam's Avatar

Join Date: Sep 2006
Location: Arizona
Photos: Gallery | Albums
Posts: 40,994
QuoteOriginally posted by zekewhipper Quote
I got an 18-55mm f3.5-5.6 WR zoom for Christmas. It of course has a twist on petal hood which I won't use as I detest that type.

For all my other lenses I use nice metal screw on hoods. When I got my 50-200mm, determining the overall size (not thread mount size, but the front end opening), was simple as the supplied hood was solid. All I had to do was measure the end diameter, and then buy a step up ring to bridge the gap between the lens and the hood's diameters. That worked like a charm for that zoom.

However, since the new hood is a petal type, that tells me that simply measuring the end diameter will not do, as the hood already is technically too small for it or else it would not be petal shaped. Does anyone have any idea of just how large the open end diameter of a solid hood should be so that you don't have vignetting at 18mm?

I already have determined that it will need to be greater than 72mm.
The petal hood is going to give you the best coverage overall, since the 18-55mm lens is pretty wide I would recommend sticking with the Pentax hood over any round hood.

Adam
PentaxForums.com Webmaster (Site Usage Guide | Site Help | My Photography)



PentaxForums.com's high server and development costs are user-supported. You can help cover those costs by donating. Or, buy your photo gear from our affiliates, Adorama, B&H Photo, or Topaz Labs, and get FREE Marketplace access - click here to see how! Trusted Pentax retailers:

01-03-2014, 05:38 PM   #3
dms
Site Supporter




Join Date: Aug 2011
Location: New York, NY
Photos: Gallery
Posts: 1,556
The optimum is a lens hood that has a sensor aspect ratio at the end--e.g. 24mmx36mm, 48mmx72mm, etc. The tulip hoods are close to this.

The circular hoods provide very poor shielding in comparison, and in any event the end size (be it rectangular or circular) depend on the hood length as well (i.e., the angle as it opens up).

On older metal lenses, you can fit a rectangular metal hood to the filter thread--e.g., the pentax takumar 24 mm rectangular hood works on the 17mm tamron Adaptall-2 lens. Similarly the 35mm takumar hood works well on the 24mm takumar lens; but I would think the newer (mostly plastic) lens bodies may not handle the weight--i.e., weight on the filter threads may cause the lens to droop--which does not happen if it bayonets on the lens outer body. Also if you drop/bump the lens hood and it is on the filter threaded end--it seems it should be more likely to damage the internal structure.

Live with/use the tulip hood, or invest in older heavy metal body non zoom manual focus lenses such as the super/S-M-C/SMC takumar lenses.

Last edited by dms; 01-03-2014 at 06:23 PM.
01-03-2014, 05:58 PM   #4
Pentaxian
Na Horuk's Avatar

Join Date: Feb 2012
Location: Slovenia, probably
Photos: Gallery | Albums
Posts: 10,332
I think the best is the hood that came with it. It was made for that lens, after all. I don't see why that hood would be bad. In fact, many of use that got a lens without a hood bought a genuine or a knock-off hood that looks just like the genuine one.

01-03-2014, 06:15 PM   #5
Pentaxian




Join Date: Oct 2009
Location: Far North Qld
Posts: 3,250
Agree.. Hoods are made for the lens and sensor ratio - not for fashion. Using the wrong hood will result in vignetting or other aberrations.

01-03-2014, 06:32 PM   #6
Veteran Member




Join Date: Jan 2013
Location: Nanaimo, British Columbia
Photos: Albums
Posts: 328
Logic would say that a hood that is the 100% best size for 18mm would be different then a hood that is 100% best size for 55mm. To ensure no vignetting you would need a hood optimized for 18mm and whenever you use any other zoom size you would lose the benefit. As you are already aware that this is why the Petal hood is used I am curious as to why you "detest" them?
01-03-2014, 10:38 PM   #7
Loyal Site Supporter
pacerr's Avatar

Join Date: Jan 2008
Location: Henry, TN
Photos: Gallery | Albums
Posts: 2,852
Any hood for a zoom lens will only be optimally effective at its minimum focal length.

To empirically determine optimum hood length, wrap a piece of dark paper around the lens (like a tube), hold it in place with a rubber band, and extend it until vignetting occurs at the critical points and desired FL(s). Use those measurements to select a commercial hood to suit your needs.

Better yet, just use the paper slip tube and pocket the $$ you'd spend. Any inefficiency owing to a non-scolloped hood will be more than compensated by having a useful hood at the longer FLs.
01-04-2014, 10:08 AM   #8
Senior Member
zekewhipper's Avatar

Join Date: Dec 2010
Photos: Albums
Posts: 298
Original Poster
O.K., so nobody knows.

I understand about possible vignetting at 18mm, that is why I already know it needs a dia. greater than 72mm.

I completely disagree that petal hoods are the best coverage, because the notches in them obviously can let light in when using the camera in orientations where the light is aligned with those openings along the long axis. Traditional round hoods are better because they provide their maximum flair protection regardless of camera orientation. That is the main reason why I will no longer use them. The petal gaps also represent increased penetration area opportunities for debris to strike the lens from the side.

Plastic hoods break when struck, metal ones don't.

Also, with metal hoods I can use circular polarizers with ease. Once you put the hood over the C-Pl, then you can simply turn the hood to adjust the C-Pl and yet still maintain maximum available flair protection. I know that some petal hoods have the removeable panel; but that can get lost, is another opening for light and debris to get through, and are awkward to use a C-Pl through anyways. They are nice in theory or in a pinch.

01-04-2014, 10:18 AM   #9
Pentaxian
Na Horuk's Avatar

Join Date: Feb 2012
Location: Slovenia, probably
Photos: Gallery | Albums
Posts: 10,332
QuoteOriginally posted by zekewhipper Quote
I completely disagree that petal hoods are the best coverage, because the notches in them obviously can let light in when using the camera in orientations where the light is aligned with those openings along the long axis.
The circular hood provides worse overall coverage than square and petal hoods. Square and petal hoods actually clip the image circle, thus less light is bouncing around the insides. A petal hood is (or should be) already as tight as possible even at the notch, and it should have even better coverage at the longer ends. A good petal or square hood will basically make the image circle the same size as the sensor. A circular hood cannot do that. But yes, a circular hood will be exactly the same regardless of orientation, while a petal or square hood won't. Hoods for wide zoom lenses are always problematic, of course, because at 18mm you need a wide hood and that hood will be almost useless at 55mm. But short of mounting a different hood for different focal length or using a rubber, collapsible hood, there is not much that can be done.

QuoteOriginally posted by zekewhipper Quote
Plastic hoods break when struck, metal ones don't.
That is a good thing, because if the camera gets bumped hood-first (which is likely, since the hood is sticking out so far) its better that the hood breaks than the lens, mount, or camera. Hood is cheapest to replace. Also, depending on the coating, a cheap metal hood can actually reflect light into the lens in some situations. This even happens with shiny metal aperture blades. Plastic hoods tend to be less reflective.

Im not trying to start an argument, but circular hoods are not "the best" option, even though they do have their advantages in some situations - most notably flexibility and cost.
01-04-2014, 12:17 PM   #10
Loyal Site Supporter
pacerr's Avatar

Join Date: Jan 2008
Location: Henry, TN
Photos: Gallery | Albums
Posts: 2,852
QuoteOriginally posted by zekewhipper Quote
I completely disagree that petal hoods are the best coverage, because the notches in them . . .


That seems sort of a 'glass is half full' approach to hoods -- although I agree that petal hoods are funky and don't much like 'em, I do use 'em on WA and normal primes. If I REALLY need a hood with a zoom lens, I custom fit one with rolled paper and a rubber band.


The shallowest notch in a petal hood is the maximum length that any cylindrical hood could be without vignetting corners at a given FL. Any extension of the circumference of the hood beyond that length that doesn't vignette is of some benefit.


Secure some dark straws/sticks around even just one quadrant of a lens with a rubber band and extend each straw until vignetting is apparent in the VF; in that manner you can map the shape of the optimum hood for yourself.


I'd also note that stray light rays that strike the clean front surface of a lens with modern coatings are progressively less of a flare problem as the angle of incidence decreases to less than 90 degrees (perpendicular) to the lens surface.


No hood at all and/or dirty glass are much greater problems for flare IME.


H2
01-04-2014, 03:47 PM   #11
Pentaxian
Oldbayrunner's Avatar

Join Date: Mar 2013
Location: Havre de Grace, MD
Posts: 1,221
Zeke.. Yes it would have to be greater than 72mm.. I have one and tried it on my 18-55mm. It vignetted pretty badly at 18mm until 24mm. Hope that helps.
01-04-2014, 10:26 PM   #12
Senior Member
zekewhipper's Avatar

Join Date: Dec 2010
Photos: Albums
Posts: 298
Original Poster
Pacerr & Oldbayrunner: Thanks for the additional information and suggestions.

I'm thinking that is I were to...
1) ...take a bit of cardboard and cut slots in it so that the longer petals jut through
2) ...bring the cardboard into contact with the shorter petals and parallel to the flange plane
3) ...mark where the arc edges of the petals touch the cardboard
4) ...draw tangential(sp?) lines to those arcs
5) ...draw perpendicular lines to the first ones that are the arc length lines to where the longer petals jut through
6) ...measure the diagonal distance through the rectangle

Then that should give me my minimum diameter for the 18mm focal length.

Last edited by zekewhipper; 01-04-2014 at 10:33 PM.
01-04-2014, 10:53 PM   #13
dms
Site Supporter




Join Date: Aug 2011
Location: New York, NY
Photos: Gallery
Posts: 1,556
A circular hood is the worst protection of the 3 types: circular, pedal shaped, rectangular--just accept this proposition.

If you want to use a circular hood, and want it to be as/more effective than the other options, I suggest you get one that works on a similar focal length lens (e.g., there are lots of older [pre AF] circular Nikon hoods--actually that was one criticism of them) and then cut out a cardboard mask (cut out a rectangle from a circular disk), blacken the inside and cut edges, and fasten it to the front of the hood--in fact you can make several that cover various FL's of your zoom. [You would experiment with the size of the rectangle--but it would be 1.5:1 aspect ratio.] (Not my original idea--comes from "Mountain Photography" by C.D. Milner, The Focal Press, 1945, page 46-49.)

You could also buy the Ambico Shade+ adjustable hood to work out the best length/opening size. I use this on some wide angle lenses--but it's likely too heavy for your application (not as a regular solution).

BTW the following has a nice summary of older Nikon lens hoods. http://www.nikonlinks.com/Third-Party/Lens-Hoods_Rick-Housh.htm

Last edited by dms; 01-04-2014 at 11:02 PM. Reason: added Nikon hoods reference/added comment on cutting rectangle.
01-04-2014, 11:10 PM   #14
dms
Site Supporter




Join Date: Aug 2011
Location: New York, NY
Photos: Gallery
Posts: 1,556
One other thought: take (black) photo tape and wrap it around the end of the pedal hood to make the closed rectangular shape. Then check out to be sure it doesn't vignette. If good to go just leave the tape, or you could replace it with blackened (outside shellacked) cardboard that you glue or tape in place. Regular photo tape is long lasting, removes w/o trace, and not messy at all--I keep short strips of it on my camera/lenses to use for all sorts of contingencies.
01-05-2014, 06:20 AM   #15
Pentaxian
Oldbayrunner's Avatar

Join Date: Mar 2013
Location: Havre de Grace, MD
Posts: 1,221
Zeke Check out these hoods;
LensHoods.com - Offical Site. The world's largest seller of Camera Lens Hoods.

I use a collapsible screw in one for my 50-200mm. I got the one that allows the lens cap to be used. I didn't get this type for my 18-55mm, I use a screw in petal type.

The aftermarket ones I tried for normal hood mounting were just too sloppy fitting for my liking so I got the screw in ones.

Last edited by Oldbayrunner; 01-05-2014 at 06:26 AM.
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
diameter, hood, k-mount, lens, lens hood, pentax lens, size, slr lens, type
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Size for 2d hood using step up ring? PBandJ Pentax SLR Lens Discussion 2 06-18-2013 12:27 PM
Lens hood for 50mm 1.4 (most effective) zoolander Troubleshooting and Beginner Help 24 01-22-2013 01:13 AM
lens cap' size for Takumar metal hood (135/2.5, 200/4) ? deejjjaaaa Troubleshooting and Beginner Help 18 09-06-2012 04:07 AM
Filter & hood size - 77mm, 72mm, or less? Kitty Troubleshooting and Beginner Help 24 01-22-2011 08:15 AM
What size lens hood for DA L 55-300? DSLRnoob Pentax SLR Lens Discussion 2 11-21-2009 05:16 PM



All times are GMT -7. The time now is 12:24 PM. | See also: NikonForums.com, part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top