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DIY Lens Hoods - no math required
Posted By: pacerr, 03-04-2011, 11:54 AM

The ultimate purpose of a lens hood is to prevent unwanted light from impinging on the front element of your lens and it doesn't have to look pretty or cost a lot to achieve that goal.

It helps if the hood's cheap, light weight, folds to take up almost no room in your kit bag.and is somewhat adjustable in length.

Here's a step-by-step description of making one such hood -- no math required. This one's made from a file folder to show the layout and it can't get much cheaper. This took all of about 30 minutes to complete including the decision to do it and processing the photos.

1. Materials: use your own judgment as to what will work and how much you want to spend. Heavy-weight file folders are a good place to start but I've made 'em from poster board as thick as that used for the back of writing tablets. Start with something dark or spray paint the end product with flat black paint for best results.

2. Layout: there's no particular advantage to using other than a square shade which avoids having to design origami-type fold lines. As you can see, unequal sides simulate the tulip-shaped hoods and can be custom trimmed to any degree of precision you wish. The width of the "box" should equal the diameter of the lens barrel at the point of attachment. You can make it a tapered cone but that just complicates things and necessitates that origami trick to fold it. A good starting length is also equal to the diameter of the lens and this can be "trimmed" by moving the hood forward or back on the lens.



A filter ring MAY be a good aid in laying out the dimensions but be sure it's the same diameter as the lens barrel.

A smaller hood might be laid out so as to have only one glue seam if the material is large enough. I suppose you could go for an octagon pattern rather than square if you wanted to get closer to a round hood but still have it easy to fold.

Why not just trace the outline of one of the tulip hoods? Well, you could do that, but remember, a primary goal is to have a collapsible hood and round or tapered designs present fold problems.

3. Assembly: Glue, tape, rubber bands -- I assume you'll sort that out in the layout. Note the fit of this pictured hood is a little "sloppy". Two reasons: there's a ridge on the lens barrel that adds about 3mm to the diameter ahead of the rubber band, and the mounting tabs are just a little wider than necessary - they're clipped in the corners here but could be trimmed to a better fit as well.



Even if you already have a hood for your lens(es) you may want to make one like this as a space and weight saving solution for the trail. This hood's 120mm inside diameter! Which one of these would you rather carry?



I don't even want to think about the priceof a replacement hood for the Tamron SP 300/2.8 shown here even if I could find one. But more inportantly, this demo model won't go to waste; it'll be painted and tucked in the kit bag for a 'sunny day' afield.

(As a side note, here's a mod I've made to my tripod legs over the years. One fixed brace is disconnected and replaced with light-weight chain and a hook so that one leg can be adjusted independently. Works quite well in tight spaces or against a wall and the brace can be reattached if desired.)


Did ya notice I can twist that hood around the barrel to catch a stray light source and slide it back an' forth to adjust the length and vignetting? Even make it oversized or cut it up or bend a corner to compensate for the lack of a perfect tulip pattern while on site.

Oh, yeah, the metal Tamron hood weighs 3/4 pound where as the cardboard one comes in at 3/4 ounce (with the rubber band)!. An' the tabs are long enough it'll fit the SP 180 and SP 80-200 as well.

I'm a lifelong fan of pragmatic, field expedient solutions that I can afford an' I'd have to take out a mortgage if I had to replace the hood for that SP 300/2.8.

Besides, it's fun to watch the guys with $$$$'s-worth of gear go dumpster-divin' after the ones you throw away when they don't have anything with 'em in the field.
H2

Last edited by pacerr; 03-08-2011 at 02:49 PM.
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03-04-2011, 02:25 PM   #2
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Great Pacerr, but not very durable.
Now, what I'd really like is a hood for my 15mm, something that looks like one of those loudspeaker horns one sees at Churchill Downs.
By the way, I've also used a large PVC reducer as a hood extension. The problem with that is the weight.
03-04-2011, 02:37 PM   #3
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QuoteOriginally posted by Ron Kruger Quote
. . . but not very durable.
Didn't I mention "cheap", as in make 'em as you need 'em? And if you loose it in the swamp ya'll only have to replace that DA 15, not the hood too!

Come on, Ron, you KNOW you want a pocket full'a cheap hoods!

H2
03-04-2011, 03:27 PM   #4
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I like your cheap and inventive approach. I'm your poorer brother in this. I just don't like your choice of material. Wind, rain and the terrain I often inhabit would ruin it too quickly.
Besides, I have no problem with the hood on my 200mm. It's the shorter FLs where I could use more shade, but thankfully they are all 49mm (filter size), so what I need is one designed for my 15mm that extends beyond the lens for up to a foot without getting into the field of view, and I'll bet I could use it on all of them.

03-04-2011, 08:33 PM   #5
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QuoteOriginally posted by Ron Kruger Quote
.... It's the shorter FLs where I could use more shade, but thankfully they are all 49mm (filter size), so what I need is one designed for my 15mm that extends beyond the lens for up to a foot without getting into the field of view, and I'll bet I could use it on all of them.
The minimum diagonal for a non-vignetting hood for your 15mm lens, 49 mm filter ring would vary with depth like:

Depth....Diameter
12".......41.3"
6".........21.6"
3".........11.8"

This was based on the front glass lens element being 49mm in diameter. I suppose it is actually a bit smaller, but that won't change the numbers much. However, a 3" deep hood (depth from glass element) will still do a lot to decrease flare-causing side light from striking the lens...like maybe cut it in half.

Dave

The equation for hood diameter that avoids vignetting is:

Hood.diameter=Lens.diameter(Hood.depth/focal.length +1)
03-05-2011, 10:12 AM   #6
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Thanks Newarts. Sometimes I wish I had payed more attention to math in school. So then I guess 30 inches wide or so would be good for a 9-inch depth.
I don't mean to impose upon your kindness, but could you run the number for 50mm, also 49mm filer size?
03-05-2011, 02:00 PM   #7
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QuoteOriginally posted by Ron Kruger Quote
Thanks Newarts. Sometimes I wish I had payed more attention to math in school. So then I guess 30 inches wide or so would be good for a 9-inch depth.
I don't mean to impose upon your kindness, but could you run the number for 50mm, also 49mm filer size?
Guessing that your 50 lens is actually about 29mm diameter (f:1.7) or 38mm (F:1.4) the hood diameter for different depths (lens to hood end) is:

Depth...F:1.7....F:1.4
1.0".......1.7".....2.2"
1.5".......2.0".....2.6"
2.0".......2.3".....3.0"
2.5".......2.6".....3.4"

Good luck!
Dave

The equation for hood diameter that avoids vignetting is:

Hood.diameter=Lens.diameter(Hood.depth/focal.length +1)
03-06-2011, 08:42 AM   #8
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Here's a cutting pattern motivated by Pacerr's DIY hood design posted above https://www.pentaxforums.com/forums/1413351-post1.html
Unfortunately, a little math is required but it is pretty simple.


Edit: The dashed lines for the petals are incorrectly placed for a square box. A revision will be up soon I hope.

The hood is the right depth for a given width (or the right width for a given depth) for a 2:3 format frame. I think a good approach might be to set the width D equal to the lens' actual outside diameter to aid in supporting the hood - just slip the hood over the lens barrel. Note that this design requires the hood be oriented properly with respect to the frame to avoid vignetting.

The hood can be stored flat and expanded for use when required.

I believe this layout is close to optimum for a square cross-sectioned hood; I say "close to" because I did not calculate the exact petal shape required and assumed a circular arc is close enough. Perhaps Lowell G can comment on the exact shape required; he's done good work on that problem.

The following graph is an estimate of the hood's effectiveness in blocking peripheral flare-inducing light for far away scenes.



Last edited by newarts; 03-07-2011 at 11:32 AM.
03-11-2011, 10:30 AM   #9
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Much as I'm enjoyin' Dave's math-based approach to this (an' yeah, I've run the numbers) I'm just too pragmatic (or lazy?) to do math AND have to build a field-expedient hood on the same day.

Here's a fruit cup container that needs only a squirt of black spray paint or a Magic Marker to become a Prized Lens Accessory of the finest kind -- a really, really cheap one! It literally took longer to set up the shot and transfer it to the computer than it did to trim the container -- or eat the contents which counts as extra benefit points.

Certainly neither precise nor optimum, but it does work for everything from my M 35mm up that has a 49mm filter ring and could be easily trimmed shorter for a wider FoV and/or larger diameter lens barrel. And I bet I'd have to search long and hard to find a scene that this hood wouldn't handle as effectively as the most expensive hood available. Plus more extra points for re-cycling?

And now you have an excuse to carry that Swiss Army knife with the neat little scissors you've never used. If they'd just make black, Styrofoam coffee cups . . .




As an interim, or ultimate, (depends on how you see it!) solution remove the glass from cheap 49mm filters and stack 'em until you begin to see vignetting -- then remove one. A little flat or semi-gloss black, spray lacquer makes 'em look nicer.

Filter rings generally absorb a lot more abuse than thin aluminum hoods and if the rim gets dinged, just replace the outer ring. Add or remove rings to suit various focal lengths for true versatility. Use a stepping ring and larger filters to build a conical hood.

You could wrap a cylinder of paper around the lens or just stack filters to determine the final length in advance if you have to find some filters.

H2

Last edited by pacerr; 05-27-2011 at 12:37 PM.
10-11-2011, 09:42 PM   #10
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Genius! I was using black fun foam and Velcro. But, due to the foam's flexible nature, the hood was always stretching out of shape.
Nice work with both hoods.
I altered your first design a bit by making the hood out of two sheets of cereal-box cardboard stacked and stuck together and then covering it all with packing tape to waterproof it, followed by a layer of black electrician's tape (as I didn't have any spray paint handy).

I'll have to give the pudding cup one a try too. I have a scratched Haze filter in a 49mm diameter that I could poke the glass out of, then super glue the pudding cup onto it so it won't fall off... perhaps...

Good ideas Pacerr! When I talk about things like these to my buddies, I just get stared at.

Gotta love the online forums.
11-15-2011, 03:32 AM   #11
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QuoteOriginally posted by pacerr Quote
Much as I'm enjoyin' Dave's math-based approach to this (an' yeah, I've run the numbers) I'm just too pragmatic (or lazy?) to do math AND have to build a field-expedient hood on the same day.

Here's a fruit cup container that needs only a squirt of black spray paint or a Magic Marker to become a Prized Lens Accessory of the finest kind -- a really, really cheap one! It literally took longer to set up the shot and transfer it to the computer than it did to trim the container -- or eat the contents which counts as extra benefit points.

Certainly neither precise nor optimum, but it does work for everything from my M 35mm up that has a 49mm filter ring and could be easily trimmed shorter for a wider FoV and/or larger diameter lens barrel. And I bet I'd have to search long and hard to find a scene that this hood wouldn't handle as effectively as the most expensive hood available. Plus more extra points for re-cycling?

And now you have an excuse to carry that Swiss Army knife with the neat little scissors you've never used. If they'd just make black, Styrofoam coffee cups . . .




As an interim, or ultimate, (depends on how you see it!) solution remove the glass from cheap 49mm filters and stack 'em until you begin to see vignetting -- then remove one. A little flat or semi-gloss black, spray lacquer makes 'em look nicer.

Filter rings generally absorb a lot more abuse than thin aluminum hoods and if the rim gets dinged, just replace the outer ring. Add or remove rings to suit various focal lengths for true versatility. Use a stepping ring and larger filters to build a conical hood.

You could wrap a cylinder of paper around the lens or just stack filters to determine the final length in advance if you have to find some filters.

H2
I'm going to give this a try right now. It's great to find a forum where people are creative

thanks
11-15-2011, 10:36 AM - 2 Likes   #12
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i didnt want to reveal my best hood making tip, but here goes...

...if you use bright yellow cardstock for the hood, you WILL attract butterflies and bees. If you are shooting close focus flowers, they will come toward you and then find the closest flowers.


my yellow hood got me these:




Last edited by mikeSF; 11-17-2011 at 07:26 AM.
11-15-2011, 10:52 AM   #13
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that reminds me, I did once make a pop-up flash diffuser out of a crystal light container...lookee here:

https://www.pentaxforums.com/forums/1158544-post13.html


it works better than a plastic film can and is good for close focus and macro shooting to take the harshness out of the popup, especially when using manual lenses, where the camera is locked at 100% flash power.
11-16-2011, 11:29 PM   #14
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QuoteOriginally posted by mikeSF Quote
if you use bright yellow cardstock for the hood, you WILL attract butterflies and bees.
Hahahaha that's Brilliant! Did you figure that out by accident, or was it intentional?
11-17-2011, 07:29 AM   #15
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QuoteOriginally posted by Gerbermiester Quote
Hahahaha that's Brilliant! Did you figure that out by accident, or was it intentional?
accident! i was shooting backlit flowers without a hood and getting flaring so i ran inside to quickly phony up a hood out of paper. all i could find was some yellow cardstock from my son, so i put it on there and suddenly became a bee magnet.
you can also wear a yellow hat. it apparently gets them to the area and then they'll look for flowers.
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