420EX and E-TTL II

[puttick]

My local dealer hinted that a replacement for the 420EX flash was imminent, though that may have been a convenient excuse as he had no 420's in stock. His argument was that it would be E-TTL II like the 580EX.

Now that set me wondering. The EOS system chart (pdf from the Canon site) explains the two systems, and states that the 580EX is E-TTL II compatible, but that the 420EX is only E-TTL compatible. I read that as being that the camera/lens has to be capable of delivering, and flash capable of using, the distance information from the lens.

A reply to this question on the EOS forum reads "ETTL-II is built into the camera and not the flash. Any EX flash will operate in ETTL-II mode if the camera, like the 20D and the DReb XT,supports it."

Which is correct?

And - does E-TTL II really make a worthwhile difference in real situations?

I was considering buying a 420EX for my 350D (Rebel XT), as I really don't want a huge flsh unit like the 580EX. One of the reasons I traded my 300D for a 350D was to be able to use FEC via the camera, as I know I would want this feature and it is absent from the 300D. Now I wonder if it is better to wait for a 42GN flash with E-TTL II compatibility.

[PacAce]

It sure would be nice if you could point to your refernce source which says that the 420EX is only ETTL compatible but not ETTL-II compatible. I have a feeling you are just misreading the information or else, the part about the 420EX was written long before the existence of ETTL-II.

[PacAce]

I was considering buying a 420EX for my 350D (Rebel XT), as I really don't want a huge flsh unit like the 580EX. One of the reasons I traded my 300D for a 350D was to be able to use FEC via the camera, as I know I would want this feature and it is absent from the 300D. Now I wonder if it is better to wait for a 42GN flash with E-TTL II compatibility.
I said it once and i'll say it again, a 42GN flash with ETTL-II compatibility is already here. It's called the 420EX. :)

[puttick]

Hi - it was from the EOS system pdf on the Canon site, found at:
http://consumer.usa.canon.com/app/pdf/d_eos/syschart012904.pdf

it reads:
Speedlite 420EX
Although 30%
smaller in total
volume than
the 580EX,
the Speedlite
420EX
provides a
powerful
Guide Number
of up to 138 (ft., ISO 100) and
the flash head can be bounced
and swiveled. It provides full E-TTL
flash and offers Canon’s Highspeed
Flash-sync, FE Lock and
Second-Curtain Sync. The 420EX
can also be used off-camera—
alone or with an unlimited number
of other 420EX and/or 580EX flash
units—for Wireless E-TTL flash.
It also has a power saving mode
which powers down the flash after
90 seconds of downtime.

Whereas in the section on the 580EX it states E-TTL II. Perhaps it is just misleading, as you say. However I have now read the "sticky" flash thread and found:
http://photonotes.org/articles/eos-flash/#ettlii
which confirms and explains exactly what you say.

Thanks for the advice! Ferreting out these details is not always easy, but it helps to be pointed in the right direction, and these forums are great for that.

Cheers
Nigel

[Hellashot]

One of the reasons I traded my 300D for a 350D was to be able to use FEC via the camera, as I know I would want this feature and it is absent from the 300D..

Did know that the hacked firmware unleashed FEC in camera in the Drebel/300D? :)

[scottbergerphoto]

The 420EX is an older flash. ETTLII wasn't around when the material for the 420 was written. It will still work in ETTLII as will the 550EX. The 580EX is the only Canon flash that takes advantage of some minor aspects of ETTLII like sending WB information to the camera. The main change in ETTLII is the switch from using the active AF points for flash metering to using all the camera's zone sensors.That is a function of the body.

[tim]

I've read information from Chuck W (forget the rest of his name) that said ETTL II is on the camera body and has nothing to do with the flash.

[Andy_T]

The main improvement of the 580 EX is that it does not just use the distance information, but also knows whether your digital camera has a crop factor and changes the zoom accordingly.

This should give you higher flash output, as the covered field of view doesn't have to be so big when using a 1.3 or 1.6 crop camera.

Best regards,
Andy

[scottbergerphoto]

I've read information from Chuck W (forget the rest of his name) that said ETTL II is on the camera body and has nothing to do with the flash.
The 580EX is currently the only flash that utilizes two aspects of ETTLII, WB and distance/crop. Yes, ETTLII is programmed into the body, but you must use the 580EX to be able to take advantage of these two functions. It's like having a tape recorder that has a larger frequency range then many microphones. To take advantage of the large frequency range, you must use a microphone that can transmit the full range to take advantage of it.

[PacAce]

Somebody correct me if I'm mistaken (but I don't think I am ;) ). I hear a lot of mention about distance whenever there is discussion about the 580EX. I just wanted to make it clear that the 580EX does NOT make use of distance information that is made available by certain lenses. Yes, it does feed WB information to the camera and it does receive the crop factor info from the newer cameras (which just so happen to also have ETTL-II instead of ETTL) so that the flash can adjust the zoom head appropriately but none of these have anything to do with ETTL-II. Nowhere is the distance info used by the flash for any of it's functions, as far as I know. The distance info, if available, is only used by the camera in the equation for determining ETTL-II flash exposure.

[scottbergerphoto]

Somebody correct me if I'm mistaken (but I don't think I am ;) ). I hear a lot of mention about distance whenever there is discussion about the 580EX. I just wanted to make it clear that the 580EX does NOT make use of distance information that is made available by certain lenses. Yes, it does feed WB information to the camera and it does receive the crop factor info from the newer cameras (which just so happen to also have ETTL-II instead of ETTL) so that the flash can adjust the zoom head appropriately but none of these have anything to do with ETTL-II. Nowhere is the distance info used by the flash for any of it's functions, as far as I know. The distance info, if available, is only used by the camera in the equation for determining ETTL-II flash exposure.
I believe that you are correct. The distance info received from the lens is used by the camera to calculate flash output.

[Andy_T]

So just get the 420EX :lol:
Everybody is confused now.

Best regards,
Andy

[Todd Jacobsen]

I believe that you are correct. The distance info received from the lens is used by the camera to calculate flash output.

This is what Canon's site says:

When the SPEEDLITE 580EX receives image size data from a supported EOS digital camera*, the flash head automatically zooms to match the effective angle of view. The resulting flash coverage is more accurate. When color temperature data is automatically transmitted from the SPEEDLITE 580EX to a camera*, the camera sets the color balance for the optimal flash shot.
* EOS 20D, EOS-1D Mark II (firmware update necessary) or later camera models

So...I believe the 580EX DOES use the distance data - from E-TTLII qualified cameras - even though the distance data is intertwined as a combination of crop & E-TTLII (camera) inputs,

[PacAce]

This is what Canon's site says:

When the SPEEDLITE 580EX receives image size data from a supported EOS digital camera*, the flash head automatically zooms to match the effective angle of view. The resulting flash coverage is more accurate. When color temperature data is automatically transmitted from the SPEEDLITE 580EX to a camera*, the camera sets the color balance for the optimal flash shot.
* EOS 20D, EOS-1D Mark II (firmware update necessary) or later camera models

So...I believe the 580EX DOES use the distance data - from E-TTLII qualified cameras - even though the distance data is intertwined as a combination of crop & E-TTLII (camera) inputs,
And where in your quote is there any mention of distance? ???

[puttick]

I am sure you'll all be pleased to know I have just ordered a 420EX, and at a superb price - I found one store (T4 phtographic) selling it at 150 UK Pounds less the promotional voucher 35 UKP, net 115 UKP (normal retail is 180 UKP). Glad to have started such a debate -and learned something in the process...

Cheers
Nigel

[PacAce]

I am sure you'll all be pleased to know I have just ordered a 420EX, and at a superb price - I found one store (T4 phtographic) selling it at 150 UK Pounds less the promotional voucher 35 UKP, net 115 UKP (normal retail is 180 UKP). Glad to have started such a debate -and learned something in the process...

Cheers
Nigel
Congrats. :)

[tim]

This is what Canon's site says:

When the SPEEDLITE 580EX receives image size data from a supported EOS digital camera*, the flash head automatically zooms to match the effective angle of view. The resulting flash coverage is more accurate. When color temperature data is automatically transmitted from the SPEEDLITE 580EX to a camera*, the camera sets the color balance for the optimal flash shot.
* EOS 20D, EOS-1D Mark II (firmware update necessary) or later camera models

So...I believe the 580EX DOES use the distance data - from E-TTLII qualified cameras - even though the distance data is intertwined as a combination of crop & E-TTLII (camera) inputs,

I think you're mistaken. The camera tells the flash what size the sensor is, and based on that the flash head only illuminates the area that the camera will take a photo of. It's an efficiency feature more than anything - it doesn't waste power and cycles faster because of that.

[Todd Jacobsen]

And where in your quote is there any mention of distance? ???

I am reading this:

When the SPEEDLITE 580EX receives image size data from a supported EOS digital camera*, the flash head automatically zooms to match the effective angle of view...

To mean this:

Subject is recognized from background. To recognize subject and "appropriate powere required" distance needs to be calculated.

Based on subject location, appropriate "crop" can be computed by 580EX based on "camera provided data" to "match the effective angle of view".

In order for the flash to appropriate light the "subject" and "crop" effectively, distance has to be a part of the calculation. This is essentially, the big difference between the 550EX and 580 - distance data - which allows one to "crop" the power effectively.

How else would the 580 know the difference between 3ft and 58ft? If this was all E-TTL, then there is NO difference between 550 and 580 (well, besides size, weight, price...).

[tim]

I don't know if the flash uses distance data, but I read that to mean the 580EX only illuminates the area that's in the frame. The idea is for 1.6X crop cameras it doesn't have to illuminate what would be the edges of the frame on a 35mm/1DsMk II, so it's more efficient. It doesn't need to know the distance to the object for that, it just needs to know the angle of view. It knows how bright it needs to flash because of its preflash.

[Todd Jacobsen]

I don't know if the flash uses distance data, but I read that to mean the 580EX only illuminates the area that's in the frame. The idea is for 1.6X crop cameras it doesn't have to illuminate what would be the edges of the frame on a 35mm/1DsMk II, so it's more efficient. It doesn't need to know the distance to the object for that, it just needs to know the angle of view. It knows how bright it needs to flash because of its preflash.

Tim,

How does the flash know "WHAT IS IN VIEW?" That's a cone that goes out to infinity from the camera lens.

1.6 is 1.6 is 1.6. There is no need to "ZOOM" if senor size is the only factor - what is viewable is constant - its 1.6. You're zooming to the two dimensional slice of the cone which is what the "distance" measurement provides. The 1.6 provides the intial "cone" size which grows (aka veiwable picture) as you approach infinity.

I cannot imagine that the "crop" is based off of "infinity" and everything before that point is "caught". This is what the 550 does.

If that's all that the 580 does, then the "crop" factor is marketing vs something real. But the 580 "zooms" based on crop...which requires distance to know where to zoom to....

[tim]

My understanding of the physics is that the lens needs to know the angle of view to illuminate and zooms its head based on that, not on the distance to the subject. No matter how far from the lens the object is, it's still based on the angle.

Hopefully someone can enlighten us both on what's going on here, and maybe explain what i'm trying to say more easily. I'm pretty sure the model I understand in my head is correct, but i'm not sure i've explained what i'm thinking well.

[Todd Jacobsen]

My understanding of the physics is that the lens needs to know the angle of view to illuminate and zooms its head based on that, not on the distance to the subject. No matter how far from the lens the object is, it's still based on the angle.

Hopefully someone can enlighten us both on what's going on here, and maybe explain what i'm trying to say more easily. I'm pretty sure the model I understand in my head is correct, but i'm not sure i've explained what i'm thinking well.


Distance from subject DEFINES the viewable area.

The viewable area SIZE changes based off of the (direct) distance from camera.

The area I see at infinity (or 58 meters in 580EX "ease) is MUCH larger than the area I see at 3 ft. To crop appropriately, the flash has to know "image size" - or better yet "image area" which is a combination of 1.6 & distance.

That's also why the "crop" game goes away when the flash is pointed anywhere other than direct - the "distance" is no longer accurate for flash compensation since distance to subject can no longer be (accurately) calculated in bounced scenarios.

[tim]

Does it matter what the distance to the subject is so long as the camera lens and flash are set at the same angle? And when you include the crop factor does that not just reduce the angle that both the camera captures and the flash has to illuminate?

[Todd Jacobsen]

Does it matter what the distance to the subject is so long as the camera lens and flash are set at the same angle? And when you include the crop factor does that not just reduce the angle that both the camera captures and the flash has to illuminate?

Your use of angle is confusing - to me.

What changes the "angle" between the camera and the flash? - DISTANCE from subject. Closer to infinity the subject is, the smaller the angle. The closer to the CAMERA the subject is, the LARGER the angle. Not sure what other angle you are referring to, other than the angle at subject location.

Flash illuminates an AREA, not an "angle". A flash CAN project at an angle. To appropriately CROP the area you want the flash to illuminate, you need to know the SIZE of that area (Image size).

Flash angle means, to me, is direct, 45 bounce, etc...Once that angle is changed, you no longer can "crop".

Crop has nothing to do with the camera per say - this is flash based. The "camera" does not know it's a 1.6 chip. This knowledge is based off of the lenses used.

Camera does not capture an "angle", it captures a two-dimensional image - with or without an in-focus subject.

It would be VERY easy for the flash to zoom for cropping by:

1) Knowing the camera (20D vs 1Ds)
2) Knowing the distance

The Image Size at 3ft for each camera is much different than the image size at 50ft. It (image size) is not the SAME for either camera at either distance, thus the power required needs to accomodate the change in size - for appropriate flash "crop" in order to conserve power.

[PacAce]

Todd, you are obviuosly confused and Tim is not.

To put it simply, all EX flashes at least from the 420EX and up, will automatically zoom their flash head to suit the lens that is being used on the camera. This is done because differrent focal lengths have different angles of view. A 24mm wide angle lens will require a wider flash coverage than a 300mm telephoto lens. Before the 580 EX came along, all the EX series flashes zoomed to whatever focal length lens was attached to the camera. For zoom lenses, the flash head adjusts itself as the lens is zoom from one focal length to another. The flash coverage provided as the head is zoom from one focal length to another, in discrete increments, was based on the 35mm format.

When the same flash is used on, say, a 1.6 crop factor camera, the flash is illuminating more area than is really required and, hence, "wastes" some flash power. The 580EX corrects that by taking into consideration the size of the sensor of the camera and adjusts the flash head zoom to only cover as much as needed. This is all a function of the sensor size and the focal length of the lens being used. There is NO distance used in the equation for any of this. The 580EX will automatically compensate for the sensor size when used with the 1DmkII and all newer cameras, and without regard to whether the lens being used provides distance information or not.

[tim]

By angle, I mean the angle of view of the lens. For example, a fisheye will have near a 180 degree field of view, and a long telephoto might have a 2 degree view. I'm going to ignore the vertical plain and concentrate on the horizontal plane.

The flash head zooms based on the length of the lens, so it covers only the area it needs to. I believe it does this based on the angle of the lens, not based on the distance to the subject. I think this because if you put a zoom lens on, with its lens cap on, and set it to 28mm the flash sets itself at the correct angle for that angle/field of view. If you zoom to 75mm the flash changes it's focus, so it illuminates a narrower angle and hence puts more light into the angle that it needs to. The closer to the camera the subject is, the less area is illuminated, but so long as the angle is the same, the flash doesn't need to know.

I tried to draw a picture but it didn't work, oh well.

Edit - what Pacace said is what I was getting at, apparently I wasn't explaining it well.

[Todd Jacobsen]

Todd, you are obviuosly confused and Tim is not.

To put it simply, all EX flashes at least from the 420EX and up, will automatically zoom their flash head to suit the lens that is being used on the camera. This is done because differrent focal lengths have different angles of view. A 24mm wide angle lens will require a wider flash coverage than a 300mm telephoto lens. Before the 580 EX came along, all the EX series flashes zoomed to whatever focal length lens was attached to the camera. For zoom lenses, the flash head adjusts itself as the lens is zoom from one focal length to another. The flash coverage provided as the head is zoom from one focal length to another, in discrete increments, was based on the 35mm format.

When the same flash is used on, say, a 1.6 crop factor camera, the flash is illuminating more area than is really required and, hence, "wastes" some flash power. The 580EX corrects that by taking into consideration the size of the sensor of the camera and adjusts the flash head zoom to only cover as much as needed. This is all a function of the sensor size and the focal length of the lens being used. There is NO distance used in the equation for any of this. The 580EX will automatically compensate for the sensor size when used with the 1DmkII and all newer cameras, and without regard to whether the lens being used provides distance information or not.

Pace,

Why is CROP dropped with Multi-Flash and ANY flash angle other than direct?

Your statements show your belief that CROP is INDEPENDENT of ANYTHING other than 1.6. Angle of flash should not THEN impact this since SENSOR size is FIXED no matter WHERE the flash is pointed. In your view, EVERYTHING, outside a simple 1.6 calculation, is decided by the camera. CROP, in your interpretation, is a marketing gimmic.

Amazing but true, all FOUR of my 580EX's inhibit this "CROP" factor when ever the 580 is pointing away from DIRECT or if MULTI-FLASH capabiity is utilized. If it was only a 1.6 factor, that shouldn't be a problem. The only thing that is changing is the variable of DISTANCE between the subject and the light source.

[Rob612]

Amazing but true, all FOUR of my 580EX's inhibit this "CROP" factor when ever the 580 is pointing away from DIRECT or if MULTI-FLASH capabiity is utilized.

Same does mine, and with it makes five of them... I do not really understood fully how the 580 works yet, but sure enough your assumption seems reasonable to me.

[PacAce]

Pace,

Why is CROP dropped with Multi-Flash and ANY flash angle other than direct?

Your statements show your belief that CROP is INDEPENDENT of ANYTHING other than 1.6. Angle of flash should not THEN impact this since SENSOR size is FIXED no matter WHERE the flash is pointed. In your view, EVERYTHING, outside a simple 1.6 calculation, is decided by the camera. CROP, in your interpretation, is a marketing gimmic.

Amazing but true, all FOUR of my 580EX's inhibit this "CROP" factor when ever the 580 is pointing away from DIRECT or if MULTI-FLASH capabiity is utilized. If it was only a 1.6 factor, that shouldn't be a problem. The only thing that is changing is the variable of DISTANCE between the subject and the light source.
Hmmm, could it be that's because when you point the flash away from direct flash, the zoom head always moves to the 24mm position? ??? And that is true for the other EX flashes as well, not just the 580EX.

And, oh, btw, the same is true when you set the flashes to wireless. The heads zoom out to the 24mm position, too, to get as wide a coverage as possible. In these cases, there is no need to adjust for the crop factore, cuz it's "the wider the better".

[Todd Jacobsen]

Hmmm, could it be that's because when you point the flash away from direct flash, the zoom head always moves to the 24mm position? ??? And that is true for the other EX flashes as well, not just the 580EX.

And, oh, btw, the same is true when you set the flashes to wireless. The heads zoom out to the 24mm position, too, to get as wide a coverage as possible. In these cases, there is no need to adjust for the crop factore, cuz it's "the wider the better".


Hmm...but crop works at 24mm direct....why isn't "wider better" in this case?

[PacAce]

Hmm...but crop works at 24mm direct....why isn't "wider better" in this case?
You're kidding me, right?

[RAitch]

(in an attempt to turn the thread from endless arguing...)

So when I go to buy an external flash for my XT, I won't miss any useful functionality if I buy a 420EX? The 550EX and 580EX seemed rich in options... but also in expense. I want something that will work well with the XT. I don't like settling for something that's not quite what I want/need... but am finding it hard to to understand the differences.

Before somebody snaps, I'll admit that I haven't read the entire sticky... but intend to.
For now, just looking for some basic info and advice.

BTW, I could care less if the flash zooms/changes angles/alters it's view/whatever else you want to call it. I don't really care if the flash wasted some power. The way light bounces and reflects off of objects, that could even be beneficial.

[Jon]

No, you won't miss any ordinarily useful functionality, just some of the frills that those of us who've been hanging around here too often and too long tend to get excessively hung up on.

[puttick]

After starting this, I'm happy now that I understand why the 420ex will work using E-TTL II, and also I understand why the zooming is affected by the crop ratio - so I will have to live with that. Given the rebate on the flash, the 420ex is 2/5 of the price of the 580ex here in UK - and that is one ratio I'm very happy with. It's also 1/2 the size, but only 1/2 stop slower. Any more figures?

I ordered the 420ex.

Nigel

[PacAce]

After starting this, I'm happy now that I understand why the 420ex will work using E-TTL II, and also I understand why the zooming is affected by the crop ratio - so I will have to live with that. Given the rebate on the flash, the 420ex is 2/5 of the price of the 580ex here in UK - and that is one ratio I'm very happy with. It's also 1/2 the size, but only 1/2 stop slower. Any more figures?

I ordered the 420ex.

Nigel
:lol: :D ;) Have fun with your new flash, Nigel. :)