Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
08-15-2016, 08:16 AM   #1
Pentaxian




Join Date: Aug 2013
Posts: 2,415
Petal vs. Pie Tin Hoods for Wide Angle Lenses?

I was intrigued by a remark by Sandy Hancock in another thread that he uses an aftermarket "petal" hood on his FA20/2.8 rather than the original "pie tin" design. I was wondering if any of y'all could elaborate on what makes the petal design better? It's an issue that's been on my mind ever since I acquired my K20/4--I could see the utility of the original hood's rectangular design, but faffing about with a clip-on seemed a bit too time-consuming while in the field. I ended up going with a Nikon HN-1 on both K20 and the K28/3.5 I own, but have always been a bit dubious that the shallow bell was giving me much advantage.


Any thoughts greatly appreciated!

08-15-2016, 08:23 AM   #2
Site Supporter
Site Supporter
jatrax's Avatar

Join Date: May 2010
Location: Washington Cascades
Photos: Gallery | Albums
Posts: 12,034
I always thought that the petal hoods were custom designed for zoom lenses and that primes could use a full circular hood because there is no need to accommodate the variable focal length.

However, I could be completely wrong and am also interested in other thoughts.
08-15-2016, 08:37 AM   #3
Pentaxian




Join Date: May 2015
Posts: 960
The petal is what's left when the geometries of the viewing cone and the sensor are subtracted from the hood. Should apply to all lenses. Petal will be less deep on wide angle.
08-15-2016, 08:44 AM   #4
Ooh! Shiney! Me Want!
Loyal Site Supporter
monochrome's Avatar

Join Date: Mar 2008
Location: Working From Home
Photos: Gallery | Albums
Posts: 26,077
I've always imagined petals might work because vignetteing is worse in the corners where petals have their openings.

08-15-2016, 09:09 AM - 1 Like   #5
Loyal Site Supporter
Loyal Site Supporter
baro-nite's Avatar

Join Date: Aug 2011
Location: North Carolina, USA
Photos: Gallery | Albums
Posts: 5,032
The ideal hood, in terms of blocking stray light, is rectangular, same proportions as the format. Petal hoods, which are more convenient to store (reversed on the lens) and carry, are a good compromise. "Pie tins" are the least effective, at least for wide angle lenses. (For long lenses circular hoods are fine, because you get good coverage without vignetting.)

Actual pie tins are a poor choice, owing to their reflectivity.
08-15-2016, 09:14 AM - 1 Like   #6
Site Supporter
Site Supporter
microlight's Avatar

Join Date: Sep 2011
Location: Hampshire, UK
Posts: 1,587
Not to mention the presence of pie.
08-15-2016, 09:20 AM - 1 Like   #7
Site Supporter
Site Supporter
Pioneer's Avatar

Join Date: Aug 2009
Location: Elko, Nevada
Photos: Gallery | Albums
Posts: 1,290
I spray paint all my pie tins flat black.

Just in case I may need one for a lens hood in an emergency.

Don't ya know...
08-15-2016, 09:21 AM   #8
Pentaxian
photoptimist's Avatar

Join Date: Jul 2016
Photos: Albums
Posts: 4,332
Petal hoods block more stray light than pie tin hoods do. The pie tin hood must be designed with a big enough opening not to vignette the corners but lets in a lot of stray light from above and below as well as some from the sides. A properly designed petal hood blocks almost all light outside of the view of the sensor and will better reduce flare and loss of contrast from the sun lighting up dust on the front elements of the lens.

The optimum shape of the petal is designed by taking a rectangular pyramid projected from the sensor through the lens with extra allowance for the lens aperture and then using that shape to clip a cylinder.

Note: petal hoods are only possible on lenses in which the front element does NOT rotate during focusing or zoom.

08-15-2016, 09:51 AM   #9
Pentaxian
D1N0's Avatar

Join Date: May 2012
Location: ---
Photos: Gallery
Posts: 6,134
Petals won't work on lenses with a rotating filter ring,
08-15-2016, 09:57 AM   #10
Pentaxian




Join Date: Aug 2013
Posts: 2,415
Original Poster
Thanks for the insights, guys--it looks as if Sandy is on to something (of course I'd imagine most Aussies know from glare.) It might be worth a few "add-on" items in my next B&H order...
08-15-2016, 01:31 PM   #11
Pentaxian
Paul the Sunman's Avatar

Join Date: Aug 2011
Location: Melbourne
Photos: Gallery
Posts: 2,584
It is interesting to look at an image from the DA 15 Limited, an APS-C lens with in-built retractable petal hood, taken in FF mode on the K1:

This is taken wide open (f/4); the boundary is much sharper at f/11.

The petal does a good job of defining a rectangular image. A round hood obviously gives a round cut-out, that must be less tight on the edges to avoid corner vignetting.
08-15-2016, 02:03 PM   #12
Pentaxian




Join Date: Aug 2013
Posts: 2,415
Original Poster
QuoteOriginally posted by Paul the Sunman Quote
defining a rectangular image

That's very interesting, thanks! To be honest, like jatrax I'd always thought petal hoods were part of the "compromise" bargain you get with zooms, but they do seem to have some neat characteristics. Of course, if a fellow was really serious about maximizing "landscape" IQ across the frame, I might have to look to some ZK mount Zeiss's and a Lee hood.
08-15-2016, 02:23 PM   #13
Loyal Site Supporter
Loyal Site Supporter
UncleVanya's Avatar

Join Date: Jul 2014
Photos: Gallery | Albums
Posts: 16,537
QuoteOriginally posted by photoptimist Quote
Note: petal hoods are only possible on lenses in which the front element does NOT rotate during focusing or zoom.
Small adjustment to this statement... Petal hood's work only when the hood doesn't rotate during use. A bayonet mounted hood on a lens with a rotating front element that doesn't rotate the hood attachment point will still work fine.

---------- Post added 08-15-16 at 05:26 PM ----------

This usually helps explain things...

https://goo.gl/images/kADQHq

---------- Post added 08-15-16 at 05:31 PM ----------

Also, zooms tend to have these goods partly because the zoom is forced to have a good that only covers the shortest focal length. Using the most compact and efficient shape is necessary to get the best coverage. As indicated a rectangle may be just as good or better, but the rectangular shape tends to scale poorly and be difficult in a bag, taking more width and sometimes making reversing the hood difficult.

Last edited by UncleVanya; 08-15-2016 at 02:31 PM.
08-15-2016, 03:53 PM   #14
Loyal Site Supporter
Loyal Site Supporter
pacerr's Avatar

Join Date: Jan 2008
Location: Paris, TN
Photos: Gallery | Albums
Posts: 3,027
Hoods are GOOD. It's also simple. Simply shade the front surface of the lens from ALL light not within the FOV of the sensor if you can.

Use your hand, hat, bumbershoot (?), -- somebody else's hand, etc. Whatever works at the moment.

Take a business card ... use a rubber band to attach it to the lens ... extend it or retract it til you can see no evidence of vignetting ... move it around the lens at 10-15-?? degree increments (or one degree if you're OCD) ... record the length from the front of the objective lens at each position. You've just defined the perfect hood for that lens (at that focal length) at that point in time.

In a general sense, if I need a hood for a zoom lens I carry more than one . . . sumpthun for each FL I'd likely use. (Better yet, a willing assistant with a hat -- or bumbershoot? (Even better if the assistant will also carry a cooler full of . . .?)

Hoods ARE good . . . but no hood's perfect. No NOTICEABLE glare/flare's the pragmatic goal. I've found a circular hood who's length is about 2/3rds the diameter of the objective lens element covers many situations.

Realistically -- practically? -- it's simple: when you're set up for a shot shade the lens with your hand in various positions. If you can see a difference in contrast or glare/flare . . . do sumthun to fix it as needed!

Last edited by pacerr; 08-15-2016 at 04:00 PM.
08-15-2016, 03:59 PM   #15
Pentaxian
photoptimist's Avatar

Join Date: Jul 2016
Photos: Albums
Posts: 4,332
QuoteOriginally posted by UncleVanya Quote
Small adjustment to this statement... Petal hood's work only when the hood doesn't rotate during use. A bayonet mounted hood on a lens with a rotating front element that doesn't rotate the hood attachment point will still work fine.
You are quite right about the precise prerequisites for a petal hood. It's not the non-roation of the front element or filter ring that matter but the bayonet or flange that holds the hood.

QuoteOriginally posted by UncleVanya Quote

---------- Post added 08-15-16 at 05:26 PM ----------

This usually helps explain things...

https://goo.gl/images/kADQHq

---------- Post added 08-15-16 at 05:31 PM ----------

Also, zooms tend to have these goods partly because the zoom is forced to have a good that only covers the shortest focal length. Using the most compact and efficient shape is necessary to get the best coverage. As indicated a rectangle may be just as good or better, but the rectangular shape tends to scale poorly and be difficult in a bag, taking more width and sometimes making reversing the hood difficult.
Quite true, too. What's interesting is that the hoods on some zooms do a decent job even zoomed in because the nodal point of the lens tends to retreat deep inside the lens during zooming. There's still some out-of-frame light hitting the front element but most of the stray light gets stopped inside the zoom's tube before hitting the deeper elements.
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!
bit, design, element, front, hood, k-mount, pentax lens, pm, post, shape, slr lens
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
LensRentals: Variance Measurement for Wide Angle Lenses interested_observer Pentax SLR Lens Discussion 3 07-19-2015 11:54 AM
For Sale - Sold: NOS Pentax K Series 52mm Wide Hoods for 28mm to 35mm lenses gofour3 Sold Items 7 08-10-2014 08:55 AM
For Sale - Sold: Two Pentax K Series 52mm Wide Hoods for 28mm to 35mm lenses gofour3 Sold Items 2 06-10-2014 06:57 AM
Need 645 Wide Angle Lens Hoods iCrop Pentax Medium Format 59 04-22-2010 07:27 AM
Lens hoods for Wide-Angle Trawlerman Pentax SLR Lens Discussion 4 04-28-2008 09:20 AM



All times are GMT -7. The time now is 03:09 PM. | See also: NikonForums.com, CanonForums.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