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FORUMS General Gear Talk Flash and Studio Lighting 
Thread started 21 Jul 2009 (Tuesday) 08:49
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Does Manual zoom on the 580EX II account for crop factor?

 
NaiohT
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Jul 21, 2009 08:49 |  #1

I was unable to find the answer in the manual, search forum or google.

But pretty simple question, when setting manual zoom on the 580EX II flash, does it account for the 1.6x crop factor.

Does it depend if you are using an EF-S lens? I.e. if using a 1.6 crop camera with an EF lens it would not recognize it?

If anyone knows it would be much appreciated.

Thanks!


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40Dude6aedyk
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Jul 21, 2009 09:41 |  #2

It would be trivial to test if I had my kit at hand: Put flash in ETTL mode and listen to the motor change the flash zoom when I change the focal length of the zoom lens and note the flash mm setting. Then switch to manual flash mode and repeat.


Canon 40D; Canon 70-200 mm f/2.8L IS, 17-55mm f/2.8 IS, 85 mm f/1.8; 580EX II; Sigma EF-530 DG Super; CyberSyncs

  
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colormaniac
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Jul 21, 2009 09:44 as a reply to  @ 40Dude6aedyk's post |  #3

I read it somewhere that it does not account for the crop factor. Cannot recall where it is and how reliable that remark is.



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SkipD
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Jul 21, 2009 10:10 |  #4

NaiohT wrote in post #8317580 (external link)
I was unable to find the answer in the manual, search forum or google.

But pretty simple question, when setting manual zoom on the 580EX II flash, does it account for the 1.6x crop factor.

Does it depend if you are using an EF-S lens? I.e. if using a 1.6 crop camera with an EF lens it would not recognize it?

There is absolutely NO DIFFERENCE between focal lengths of an EF-S series lens as compared to an EF series lens. For example, an EF-S zoom set to 50mm will provide precisely the same field (angle) of view as an EF 50mm lens.

ALL camera lenses for SLRs are marked with their actual focal length (or focal length range in the case of zoom lenses) and not some "equivalent" value based on any particular camera format.

Canon's Speedlite flash units' focal length numbers are based on the 35mm film format. The newer Speedlites know when they are being used on an APS-C body and use a different setting for the projection angle as a result when in ETTL mode. It does not matter which family of Canon lens you are using, as only the focal length matters.

I don't know for sure, but I strongly suspect that if you are using a newer Speedlite in manual and setting the projection angle by reading the "focal length" display on the Speedlite you will have to apply the "crop factor" manually. Multiply the focal length of your lens by 1.6 and use that value for setting the flash unit's projection angle.


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adsayer
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Jul 21, 2009 10:12 |  #5

yep the mkII does compensate for a cropped sensor by default... you can disable it through a Custom Function though if you wish.

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SkipD
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Jul 21, 2009 10:24 |  #6

adsayer wrote in post #8317998 (external link)
yep the mkII does compensate for a cropped sensor by default... you can disable it through a Custom Function though if you wish.

Does it do that when the flash is being set up in manual mode and not ETTL?

Also - just to be totally clear, which "mkII" Speedlite are you referring to?


Skip Douglas
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NaiohT
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Jul 21, 2009 11:13 |  #7

Skip,

By this, I meant that the flash may be able to recognize the lens as EF-S but not the crop factor of the camera, and knowing that an EF-S only fits on cameras with a 1.6 crop, it would make the proper adjustments.

Thank you for the clear answer though, seems i'll do some fooling around with it this evening!

SkipD wrote in post #8317990 (external link)
There is absolutely NO DIFFERENCE between focal lengths of an EF-S series lens as compared to an EF series lens. For example, an EF-S zoom set to 50mm will provide precisely the same field (angle) of view as an EF 50mm lens.

ALL camera lenses for SLRs are marked with their actual focal length (or focal length range in the case of zoom lenses) and not some "equivalent" value based on any particular camera format.

Canon's Speedlite flash units' focal length numbers are based on the 35mm film format. The newer Speedlites know when they are being used on an APS-C body and use a different setting for the projection angle as a result when in ETTL mode. It does not matter which family of Canon lens you are using, as only the focal length matters.

I don't know for sure, but I strongly suspect that if you are using a newer Speedlite in manual and setting the projection angle by reading the "focal length" display on the Speedlite you will have to apply the "crop factor" manually. Multiply the focal length of your lens by 1.6 and use that value for setting the flash unit's projection angle.


|| Canon XSi/450D || Canon 18-200 f/3.5-5.6 || Sigma 28-60 f/3.5-5.6 || Canon 580EX II || Manfrotto 055XB & 488RC2 ||
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SkipD
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Jul 21, 2009 11:50 |  #8

NaiohT wrote in post #8318383 (external link)
Skip,

By this, I meant that the flash may be able to recognize the lens as EF-S but not the crop factor of the camera, and knowing that an EF-S only fits on cameras with a 1.6 crop, it would make the proper adjustments.

Thank you for the clear answer though, seems i'll do some fooling around with it this evening!

It does not make any engineering sense whatsoever for a flash unit to attempt to recognize the difference between an EF and an EF-S lens. The reason, as I stated before, is that focal length is focal length.

There's no difference at all (of the field or angle of view, that is) between two different design lenses (such as EF-S and EF) that are the same focal length and are used on the same camera.

The ONLY thing that makes sense is the Canon Speedlites recognizing the format of the camera to alter the angle of the light beam from the flash unit.

Now, the question is whether or not the Speedlite modifies the angle of the light beam in a similar way when it is in manual mode. I seriously doubt that if you dial in "35mm" manually that the flash will act any differently when mounted to different format cameras. When used in ETTL mode, we know it does.


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Curtis ­ N
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Jul 21, 2009 12:04 |  #9

When manually zooming the 580EX II, it will cover the field of view of the displayed focal length on a 35mm camera (24mmx36mm sensor). In other words, there is no accounting for the camera's crop factor.

When set to autozoom, it will automatically adjust for the camera's crop factor by default. This can be disabled by custom function.

Note: Manual zoom and autozoom options are always available, whether the flash is in manual or E-TTL mode.

So if, for example, you were using a 70-200 lens on a 1.6x camera, you could manually zoom the flash to 105mm and it would still cover the FOV when you zoomed the lens to 70mm. With the same lens on the same camera in autozoom mode, the flash head would never move. The display on the flash will change from 70mm to 105mm when you zoom the lens but in reality, the flash isn't adjusting anything, since it's maxed out all the time.


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adsayer
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Jul 21, 2009 12:18 |  #10

SkipD wrote in post #8318086 (external link)
Does it do that when the flash is being set up in manual mode and not ETTL?

Also - just to be totally clear, which "mkII" Speedlite are you referring to?

Oops missed the 'manual' bit of the post and title.

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Does Manual zoom on the 580EX II account for crop factor?
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