What's the difference between the petal lens hoods and the round ones?

ZombieArmy · 08-17-2015, 04:51 PM

Besides the petal one looking cooler that is

MadMathMind · 08-17-2015, 04:56 PM

Petal hoods are made for zooms that have wide-angle capabilities. Round ones are used for primes and telephoto zooms.

DeadJohn · 08-17-2015, 05:16 PM

The petal hoods are needed with many wide angle lenses. A round hood would either cause vignetting (darkening) in the corners, or would have to be so shallow that it wouldn't block any glare.

In theory, telephoto lenses could use a petal hood with long corners and even longer edges, but a consistent long length works well enough.

adpo · 08-17-2015, 05:18 PM

Petal hoods are usually optimized for a certain focal length so as to get maximum coverage without vignetting. Take the shortest edge of the petal hood and slice off the rest and you get the optimal circle hood for said focal length.

**UncleVanya** · 08-17-2015, 05:27 PM - **1 Like**

This explains it better than words:
http://i.stack.imgur.com/rg1A9.png
(In context found on this page: http://photo.stackexchange.com/questions/399/why-are-some-lens-hoods-petal-s...and-others-not)

The projected image on the sensor is rectangular. The most efficient (smallest amount of material, best coverage) for a given diameter hood is a petal shape. The rectangular hood is the next most efficient and last is the circle. Note I'm not saying that there is a best hood - because you can make a giant hood bigger than a room and it will block more than my tiny petal hood. But for a given size constraint the petal comes out on top.

**Digitalis** · 08-17-2015, 05:46 PM

Originally posted by MadMathMind

Petal hoods are made for zooms that have wide-angle capabilities.

....Really?

Originally posted by UncleVanya

The projected image on the sensor is rectangular. The most efficient (smallest amount of material, best coverage) for a given diameter hood is a petal shape.

The additional purpose for the petal shape is also that it uses less material and is a bit lighter than a bucket, or rectangular hood.Also using less material to construct it also makes producing the hood a bit cheaper. Rectangular lens hoods are more common with High end lenses from manufacturers like Voigtlander, Leica, and Zeiss - though for rangefinders vented lens hoods are also common (so the lens hood itself doesn't obstruct the RF windows) the vents also serve to make the hood lighter.

audiobomber · 08-17-2015, 05:47 PM

Originally posted by UncleVanya

The projected image on the sensor is rectangular. The most efficient (smallest amount of material, best coverage) for a given diameter hood is a petal shape. The rectangular hood is the next most efficient and last is the circle.

Why would a petal would be more effective than a rectangular hood? A petal is the best compromise to accommodate a zoom. For a fixed focal length, clearly a minimum sized rectangle with the same shape as the sensor is best.

Last edited by audiobomber; 08-17-2015 at 05:55 PM.

**UncleVanya** · 08-17-2015, 05:59 PM

Originally posted by audiobomber

Why would a petal would be more effective than a rectangular hood? A petal is the best compromise to accommodate a zoom. For a fixed focal length, clearly a minimum sized rectangle with the same shape as the sensor is best.

I disagree. The rectangle doesn't give as much coverage as it can. It's a compromise and you can see this in the picture that I posted. The myth that this is somehow related to zooms is prevalent but there is nothing scientific about it that I can find. Think about how a rectangle would look on the projected light on that picture - it would fall short in some areas of reaching it - which means that stray light would be able to leak in and potentially reduce contrast. This would be on the sides and the top towards the middle of each flat part.

---------- Post added 08-17-15 at 09:02 PM ----------

Originally posted by Digitalis

The additional purpose for the petal shape is also that it uses less material and is a bit lighter than a bucket, or rectangular hood.Also using less material to construct it also makes producing the hood a bit cheaper. Rectangular lens hoods are more common with High end lenses from manufacturers like Voigtlander, Leica, and Zeiss - though for rangefinders vented lens hoods are also common (so the lens hood itself doesn't obstruct the RF windows) the vents also serve to make the hood lighter.

I think also those shapes are associated in people's minds with quality not mass consumer goods so there is an expectation bias towards those that may drive their use in that market.

audiobomber · 08-17-2015, 06:10 PM

Originally posted by UncleVanya

I disagree. The rectangle doesn't give as much coverage as it can. It's a compromise and you can see this in the picture that I posted. The myth that this is somehow related to zooms is prevalent but there is nothing scientific about it that I can find. Think about how a rectangle would look on the projected light on that picture - it would fall short in some areas of reaching it - which means that stray light would be able to leak in and potentially reduce contrast. This would be on the sides and the top towards the middle of each flat part.

I disagree. I can't see any justification for what you're saying. When the shape of the image and the shape and length of the hood match, you will have perfect coverage. The image you showed is a rectangle, not a petal. If you create a perfect rectangle shape for a FFL lens, and add some material in the center to make it a petal, it will create a shadow.

**Digitalis** · 08-17-2015, 06:11 PM

Originally posted by UncleVanya

Think about how a rectangle would look on the projected light on that picture - it would fall short in some areas of reaching it - which means that stray light would be able to leak in and potentially reduce contrast.

In defense of rectangular lens hoods, I have had issues with petal lens hoods, with stray light leaking in through the gaps plenty of times - this would not have happened at all with a rectangular or Bucket lens hood. Though I view bucket lens hoods as being the least effective design and the most likely to contribute to vignetting. The main drawback of Rectangular lens hoods is that isn't possible to reverse them on the lens for storage.

**UncleVanya** · 08-17-2015, 06:29 PM

Originally posted by audiobomber

I disagree. I can't see any justification for what you're saying. When the shape of the image and the shape and length of the hood match, you will have perfect coverage. The image you showed is a rectangle, not a petal. If you create a perfect rectangle shape for a FFL lens, and add some material in the center to make it a petal, it will create a shadow.

What image are you looking at?

Oh I see what you saw. The orange part is the part that is the hood. The white is showing the light that makes it to the surface of the sensor. Look at the top and sides and see that the corners are where the hood is at the shortest. If you then cut the hood off to that size there would be sizable leaks of light. And yes if the hood were wider (rectangle) then perhaps this would be less of an issue. I think it is very difficult to judge these fully without math and specific lenses.

---------- Post added 08-17-15 at 09:32 PM ----------

Originally posted by Digitalis

In defense of rectangular lens hoods, I have had issues with petal lens hoods, with stray light leaking in through the gaps plenty of times - this would not have happened at all with a rectangular or Bucket lens hood. Though I view bucket lens hoods as being the least effective design and the most likely to contribute to vignetting. The main drawback of Rectangular lens hoods is that isn't possible to reverse them on the lens for storage.

I would argue that any hood can be too short for conditions. There is a limit to practical design. If you had two hoods one petal and one rectangle with the distance from the front element the same and the width the same overall then the petal wins. A rectangle due to the width can be wider and perhaps then longer so that it doesn't interfere. I think both shapes work well. The truth is there are no perfect hoods.

Just a final thought - I can absolutely see that a longer wide rectangular hood could be designed to intersect that light pattern farther out. It would be larger and bulkier but could have better coverage than what I was visualizing. But at the same time - the petal would be smaller and lighter for similar coverage.

I have that hood you have there or more accurately a JJC reproduction of it - it is a pain when fitted backwards but it can be done - just awkward.

**Digitalis** · 08-17-2015, 06:40 PM

Originally posted by UncleVanya

The truth is there are no perfect hoods*.

Agreed.

**UncleVanya** · 08-17-2015, 06:44 PM

Originally posted by Digitalis

Agreed.

* sorry, I had to edit this to make sense.

I stole your edit and included it.

Thanks.

BrianR · 08-17-2015, 06:48 PM

Here's some more diagrams of different hood shapes and a good discussion of hoods in general: Lens hoods. Figure 1 is worth considering when thinking about the "best" hood, it illustrates UncleVanya's point about a room sized hood (though on a saner scale

), along with the relevance of the real-world constraints he keeps mentioning ('for a given diameter' etc.).

Personally, I think the best design is a metal petal hood that's been sharpened to a razor's edge. Ideal in any kind of crowded situation

.

audiobomber · 08-17-2015, 06:49 PM

Originally posted by UncleVanya

The truth is there are not any perfect hoods.

A rectangular hood with the same aspect ratio as the sensor, extended to the absolute maximum length on a FFL lens without vignetting, will provide perfect shade. But perhaps that does not make it a perfect hood, since there are other factors one might consider (size, availability, cost, ease of use, filter compatibility, price, interchangeability, etc.)

08-17-2015, 04:51 PM	#1
ZombieArmy Pentaxian Join Date: Jun 2014 Location: Florida Posts: 3,210	What's the difference between the petal lens hoods and the round ones? Besides the petal one looking cooler that is

08-17-2015, 06:29 PM	#11
UncleVanya Loyal Site Supporter Join Date: Jul 2014 Photos: Gallery \| Albums Posts: 28,406	Originally posted by audiobomber I disagree. I can't see any justification for what you're saying. When the shape of the image and the shape and length of the hood match, you will have perfect coverage. The image you showed is a rectangle, not a petal. If you create a perfect rectangle shape for a FFL lens, and add some material in the center to make it a petal, it will create a shadow. What image are you looking at? Oh I see what you saw. The orange part is the part that is the hood. The white is showing the light that makes it to the surface of the sensor. Look at the top and sides and see that the corners are where the hood is at the shortest. If you then cut the hood off to that size there would be sizable leaks of light. And yes if the hood were wider (rectangle) then perhaps this would be less of an issue. I think it is very difficult to judge these fully without math and specific lenses. ---------- Post added 08-17-15 at 09:32 PM ---------- Originally posted by Digitalis In defense of rectangular lens hoods, I have had issues with petal lens hoods, with stray light leaking in through the gaps plenty of times - this would not have happened at all with a rectangular or Bucket lens hood. Though I view bucket lens hoods as being the least effective design and the most likely to contribute to vignetting. The main drawback of Rectangular lens hoods is that isn't possible to reverse them on the lens for storage. I would argue that any hood can be too short for conditions. There is a limit to practical design. If you had two hoods one petal and one rectangle with the distance from the front element the same and the width the same overall then the petal wins. A rectangle due to the width can be wider and perhaps then longer so that it doesn't interfere. I think both shapes work well. The truth is there are no perfect hoods. Just a final thought - I can absolutely see that a longer wide rectangular hood could be designed to intersect that light pattern farther out. It would be larger and bulkier but could have better coverage than what I was visualizing. But at the same time - the petal would be smaller and lighter for similar coverage. I have that hood you have there or more accurately a JJC reproduction of it - it is a pain when fitted backwards but it can be done - just awkward. Last edited by UncleVanya; 08-17-2015 at 06:44 PM.

08-17-2015, 06:40 PM	#12
Digitalis Site Supporter Join Date: Mar 2009 Location: Melbourne, Victoria Photos: Gallery Posts: 11,694	Originally posted by UncleVanya The truth is there are no perfect hoods. Agreed. Last edited by Digitalis; 08-18-2015 at 01:09 AM.*

08-17-2015, 06:48 PM	#14
BrianR Veteran Member Join Date: Dec 2010 Location: Ontario Photos: Gallery Posts: 3,332	Here's some more diagrams of different hood shapes and a good discussion of hoods in general: Lens hoods. Figure 1 is worth considering when thinking about the "best" hood, it illustrates UncleVanya's point about a room sized hood (though on a saner scale), along with the relevance of the real-world constraints he keeps mentioning ('for a given diameter' etc.). Personally, I think the best design is a metal petal hood that's been sharpened to a razor's edge. Ideal in any kind of crowded situation.

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08-17-2015, 04:56 PM	#2
MadMathMind Veteran Member Join Date: Dec 2013 Location: Houston, TX Photos: Gallery Posts: 1,717	Petal hoods are made for zooms that have wide-angle capabilities. Round ones are used for primes and telephoto zooms.

08-17-2015, 05:16 PM	#3
DeadJohn Pentaxian Join Date: Jan 2011 Location: New York Posts: 4,834	The petal hoods are needed with many wide angle lenses. A round hood would either cause vignetting (darkening) in the corners, or would have to be so shallow that it wouldn't block any glare. In theory, telephoto lenses could use a petal hood with long corners and even longer edges, but a consistent long length works well enough.

08-17-2015, 05:18 PM	#4
adpo Veteran Member Join Date: Apr 2011 Location: Arizona Photos: Gallery Posts: 888	Petal hoods are usually optimized for a certain focal length so as to get maximum coverage without vignetting. Take the shortest edge of the petal hood and slice off the rest and you get the optimal circle hood for said focal length.

08-17-2015, 05:27 PM - 1 Like	#5
UncleVanya Loyal Site Supporter Join Date: Jul 2014 Photos: Gallery \| Albums Posts: 28,406	This explains it better than words: http://i.stack.imgur.com/rg1A9.png (In context found on this page: http://photo.stackexchange.com/questions/399/why-are-some-lens-hoods-petal-s...and-others-not) The projected image on the sensor is rectangular. The most efficient (smallest amount of material, best coverage) for a given diameter hood is a petal shape. The rectangular hood is the next most efficient and last is the circle. Note I'm not saying that there is a best hood - because you can make a giant hood bigger than a room and it will block more than my tiny petal hood. But for a given size constraint the petal comes out on top.

08-17-2015, 05:46 PM	#6
Digitalis Site Supporter Join Date: Mar 2009 Location: Melbourne, Victoria Photos: Gallery Posts: 11,694	Originally posted by MadMathMind Petal hoods are made for zooms that have wide-angle capabilities. ....Really? Originally posted by UncleVanya The projected image on the sensor is rectangular. The most efficient (smallest amount of material, best coverage) for a given diameter hood is a petal shape. The additional purpose for the petal shape is also that it uses less material and is a bit lighter than a bucket, or rectangular hood.Also using less material to construct it also makes producing the hood a bit cheaper. Rectangular lens hoods are more common with High end lenses from manufacturers like Voigtlander, Leica, and Zeiss - though for rangefinders vented lens hoods are also common (so the lens hood itself doesn't obstruct the RF windows) the vents also serve to make the hood lighter.

08-17-2015, 05:47 PM	#7
audiobomber Veteran Member Join Date: May 2008 Location: Sudbury, Ontario Photos: Albums Posts: 6,806	Originally posted by UncleVanya The projected image on the sensor is rectangular. The most efficient (smallest amount of material, best coverage) for a given diameter hood is a petal shape. The rectangular hood is the next most efficient and last is the circle. Why would a petal would be more effective than a rectangular hood? A petal is the best compromise to accommodate a zoom. For a fixed focal length, clearly a minimum sized rectangle with the same shape as the sensor is best. Last edited by audiobomber; 08-17-2015 at 05:55 PM.

08-17-2015, 05:59 PM	#8
UncleVanya Loyal Site Supporter Join Date: Jul 2014 Photos: Gallery \| Albums Posts: 28,406	Originally posted by audiobomber Why would a petal would be more effective than a rectangular hood? A petal is the best compromise to accommodate a zoom. For a fixed focal length, clearly a minimum sized rectangle with the same shape as the sensor is best. I disagree. The rectangle doesn't give as much coverage as it can. It's a compromise and you can see this in the picture that I posted. The myth that this is somehow related to zooms is prevalent but there is nothing scientific about it that I can find. Think about how a rectangle would look on the projected light on that picture - it would fall short in some areas of reaching it - which means that stray light would be able to leak in and potentially reduce contrast. This would be on the sides and the top towards the middle of each flat part. ---------- Post added 08-17-15 at 09:02 PM ---------- Originally posted by Digitalis The additional purpose for the petal shape is also that it uses less material and is a bit lighter than a bucket, or rectangular hood.Also using less material to construct it also makes producing the hood a bit cheaper. Rectangular lens hoods are more common with High end lenses from manufacturers like Voigtlander, Leica, and Zeiss - though for rangefinders vented lens hoods are also common (so the lens hood itself doesn't obstruct the RF windows) the vents also serve to make the hood lighter. I think also those shapes are associated in people's minds with quality not mass consumer goods so there is an expectation bias towards those that may drive their use in that market.

08-17-2015, 06:10 PM	#9
audiobomber Veteran Member Join Date: May 2008 Location: Sudbury, Ontario Photos: Albums Posts: 6,806	Originally posted by UncleVanya I disagree. The rectangle doesn't give as much coverage as it can. It's a compromise and you can see this in the picture that I posted. The myth that this is somehow related to zooms is prevalent but there is nothing scientific about it that I can find. Think about how a rectangle would look on the projected light on that picture - it would fall short in some areas of reaching it - which means that stray light would be able to leak in and potentially reduce contrast. This would be on the sides and the top towards the middle of each flat part. I disagree. I can't see any justification for what you're saying. When the shape of the image and the shape and length of the hood match, you will have perfect coverage. The image you showed is a rectangle, not a petal. If you create a perfect rectangle shape for a FFL lens, and add some material in the center to make it a petal, it will create a shadow.

08-17-2015, 06:11 PM	#10
Digitalis Site Supporter Join Date: Mar 2009 Location: Melbourne, Victoria Photos: Gallery Posts: 11,694	Originally posted by UncleVanya Think about how a rectangle would look on the projected light on that picture - it would fall short in some areas of reaching it - which means that stray light would be able to leak in and potentially reduce contrast. In defense of rectangular lens hoods, I have had issues with petal lens hoods, with stray light leaking in through the gaps plenty of times - this would not have happened at all with a rectangular or Bucket lens hood. Though I view bucket lens hoods as being the least effective design and the most likely to contribute to vignetting. The main drawback of Rectangular lens hoods is that isn't possible to reverse them on the lens for storage.

08-17-2015, 06:44 PM	#13
UncleVanya Loyal Site Supporter Join Date: Jul 2014 Photos: Gallery \| Albums Posts: 28,406	Originally posted by Digitalis Agreed. * sorry, I had to edit this to make sense. I stole your edit and included it. Thanks.

08-17-2015, 06:49 PM	#15
audiobomber Veteran Member Join Date: May 2008 Location: Sudbury, Ontario Photos: Albums Posts: 6,806	Originally posted by UncleVanya The truth is there are not any perfect hoods. A rectangular hood with the same aspect ratio as the sensor, extended to the absolute maximum length on a FFL lens without vignetting, will provide perfect shade. But perhaps that does not make it a perfect hood, since there are other factors one might consider (size, availability, cost, ease of use, filter compatibility, price, interchangeability, etc.)