Enable auto-ISO with flash?

[camera7]

Canon EOS cameras use fixed "auto" setting of ISO 400 when using flash. Would be tremendous help if this could change through ML 

[larrycafe]

the AUTOEXPO module should help.

[camera7]

I'd like to set the manual time somewhere between 1/100 - 1/200 (within the flash sync range) and manual aperture (usually fully open for blurred backgrounds indoors) and let the ISO change automatically throughout the range: 100-20000 with the subtle fill flash on. But the auto-ISO is stuck at 400 and I have to change it manually every time the light changes. This is a pain in Canon cameras.

I'm totally new to ML. Only tested the stable version in my second camera: 550D. Do you think what you call "AUTOEXPO" could help? Can you explain or give me a link?

[Audionut]

Autoexpo is a P mode.  It's enabled when the camera is in M mode to bypass stupid Canon restrictions.

http://www.magiclantern.fm/forum/index.php?topic=7208.0

It doesn't (currently) limit shutter to sync speed though.

For flash photography, think about setting your camera into M mode.  Put the flash in E-TTL mode, in this mode the camera will only use the flash to fill in the shadows.  You might want to dial in a little negative flash exposure compensation.
You can then dial in the ambient/flash exposure ratio with shutter/ISO.  Brighter ambient = darker flash.  Since shutter is almost always fixed, the only change needed is ISO. 

Hint:  Put your ISO setting into full stop increments (since digital ISOs are useless) and use the shutter to dial in 1/3rd stop changes in balance.


I don't see how this request can be filled as there is no way to determine the ambient/flash exposure ratios.  Do you want a high ISO to boost the ambient exposure, or do you want a low ISO for less noise.

[Marsu42]

For flash photography, think about setting your camera into M mode.

M is for controlled lighting, but doesn't work for quickly changing lighting outdoors, that's why I often use Av and change ambient/flash ratio with ec.

Edit: Btw: The autoexpo module *could* be used to re-implement a better Av and Tv mode since M is the only mode in which ml can set both shutter & aperture, but it isn't there yet.

Canon EOS cameras use fixed "auto" setting of ISO 400 when using flash. Would be tremendous help if this could change through ML 

What you want is the "ML Auto ISO" function, I use it on 75% of my shots overall and 90% of my flash shots.

Unfortunately, it was recently removed because it was said to be obsolete, which is not the case as this thread again shows - so use an older ml build or wait until someone re-adds the feature as a module, I will if I find the time.

[camera7]

Yes, I normally use Av setting and keep changing the ISO manually. I always want to boost the ambient lighting and compensate the flash 1-2 full steps down often using orange gel + as big softbox as practical. Photographing events I need to react fast and Av gives me some  2-3 stops flexibility as auto exposure below 1/200s before modifying the ISO setting. The good thing about Canon is that it limits the exposure time below the sync speed - which I want. It works that way but could be done smarter with automated ISO range.

[Audionut]

M is for controlled lighting,

M mode is for creative control!

-------------------

I often fear that people limit themselves from the M mode for fear of understanding the function as it was designed (there's a lot of settings to change so it must be to hard and slow).  All other Canon modes are limited, limited in there ability to give the user direct creative control over every lighting condition.  M mode is limited only by the users ability to think on their feet.

When you learnt to tie shoe laces, did you try once and give up because it was to hard!

-------------------

but doesn't work for quickly changing lighting outdoors, that's why I often use Av and change ambient/flash ratio with ec.

It doesn't?

E-TTL is already giving you automatic flash exposure ratio.  It's calculation of the required flash exposure ratio is controlled directly through FEC.  It's smart because it doesn't overexpose (unless you specifically tell it too), it will only fill in the shadows.  note:  An extremely underexposed ambient exposure has become a shadow exposure.  Flash power will increase greatly as it is now required to fill in the entire exposure.

Ambient exposure ratio is controlled directly through ISO.  In manual flash mode, ambient exposure is controlled directly with shutter, since ISO has a direct control over both ambient and flash exposures, ie: bump ISO 1 stop and you bump both ambient and flash exposures by 1 stop.  In E-TTL flash mode, ISO controls the ratio of the dual exposure, since flash power is a ratio of ambient exposure, ie: with an increase in ISO you increase EV of the ambient exposure, but you decrease the EV of the flash exposure.

Flash photography is a very fine balance of ambient and flash exposures.  I still don't see how an auto ISO mode helps to control this ratio.  At best, it is a minimum ambient exposure adjustment.  A limited one at that.

What you want is the "ML Auto ISO" function,

With no creative control.  But you have creative control with EC?  If you can find the time to adjust EC (limited to shutter control in Canon modes), I can't fathom how the manual adjustment of ISO is any different.

Please don't use statements such as, "it can't" and, "it doesn't".  M mode is limited solely by the users understanding and ability.

[Audionut]

After reading what I wrote above, I guess I can see how an autoISO mode could be useful.

Ambient exposure must remain in a specific target exposure range.

[Marsu42]

Flash photography is a very fine balance of ambient and flash exposures.  I still don't see how an auto ISO mode helps to control this ratio. At best, it is a minimum ambient exposure adjustment.  A limited one at that.

Who said that it's for controlling the flash/ambient ratio? The min. shutter speed  is a very important feature, it works well and I don't see any limitation -  being stuck at iso 400 means too slow or too fast (> x-sync) shutter speeds in Av. The second reason is that iso 400 has more noise, it's better to shoot at lower iso if possible.

With no creative control.  But you have creative control with EC?  If you can find the time to adjust EC (limited to shutter control in Canon modes), I can't fathom how the manual adjustment of ISO is any different.

Adjusting ec: turn the back dial. Adjusting iso: press top button, turn dial. Yes, this is a speed difference that matters. Plus I have set iso steps in full stops, and ec in 1/3 steps.

M mode is limited solely by the users understanding and ability.

So you're saying that anyone who cannot shoot in M in any situation doesn't understand it or isn't able to? Wow, that's bold, in addition to being incorrect. I suggest you do more action photography with severely changing light condition in every shot in M (or auto-ettr for that matter), then think again...

... because as you wrote ettl tries to compensate for underexposed areas that the flash light covers, but on the other side of the histogram it doesn't protect you from blown highlights, that's when you need to modify iso/t settings in M or use a quicker semi-automatic mode that does it for you.

Edit: I wrote my post in parallel to yours, congrats for understanding the issue :-)

[Audionut]

So you're saying that anyone who cannot shoot in M in any situation doesn't understand it or isn't able to?

No.  Go and read my statement again.  Then take my statement in context with your own "bold" claims.

M is for controlled lighting, but doesn't work for quickly changing lighting outdoors

I suggest you do more action photography with severely changing light condition in every shot in M (or auto-ettr for that matter), then think again...

Severely changing lighting conditions in every shot!  Care to elaborate?

My idea of severely changing lighting condition is along the lines of taking shots indoors, and moving outdoors.  Since I am not (thought) limited in my exposure choices by auto modes, I make a conscious decision to adjust exposure as I walk out the door.

but on the other side of the histogram it doesn't protect you from blown highlights

Yes it does, for the flash exposure.  If you're ambient exposure if overexposed, that's of no fault or concern of E-TTL.  E-TTL is for automatic flash exposure ratio.

Who said that it's for controlling the flash/ambient ratio?

ISO?

Ambient exposure ratio is controlled directly through ISO.  In manual flash mode, ambient exposure is controlled directly with shutter, since ISO has a direct control over both ambient and flash exposures, ie: bump ISO 1 stop and you bump both ambient and flash exposures by 1 stop.  In E-TTL flash mode, ISO controls the ratio of the dual exposure, since flash power is a ratio of ambient exposure, ie: with an increase in ISO you increase EV of the ambient exposure, but you decrease the EV of the flash exposure.

Flash photography always has 2 exposures.  The ambient exposure and the flash exposure.

Don't believe me, put your flash in manual mode.  Adjust shutter duration.  What changed in the exposure?

[Marsu42]

Severely changing lighting conditions in every shot!  Care to elaborate?

Yes, I'd be delighted - because this issue comes up again and again, and it seems the ml devs shoot in different situations than I do, and that's where the "just use auto-ettr" etc. confusion comes from. Apart from that, I'll leave it here since there now seems to be an agreement that flash auto iso is useful, and that's what this thread is about.

If you shoot outdoors in hard light (daylight w/o clouds) in one second you shoot a backlit object (sun in front of you), then in the next second front-lit (sun behind you). I use a flash bracket to get the flash light where I want it for side-lit objects, and I often have to change camera ec (to protect against blown highlights), fec (to get the flash to be as unobtrusive as possible) or toggle the flash from ettl to full power m (the latter works better for very strong fill flash).

In this situations I need a semi-automatic mode because I want to a) pre-select the depth of field, b) have a min. shutter speed with ml auto iso, c) don't have the time to change yet another setting in camera m mode.

[a1ex]

In these situations, here's what I do:

1) enable auto ETTR (on the SET key) and dual ISO (once, before starting to shoot)

2) press SET once the lighting changes (takes ~3 seconds to get accurate exposure metering)

3) shoot (no flash needed, dual ISO and my color grading script will take care of the shadows)

There's still something that I want to try for auto ETTR: link to auto expo module (so ETTR will provide an exposure compensation) or to Canon metering (for instant updates outside LV - though I'm not sure if this will actually help or will screw up everything).

[Marsu42]

1) enable auto ETTR (on the SET key) and dual ISO (once, before starting to shoot)

Hey, this was only added yesterday :->

2) press SET once the lighting changes (takes ~3 seconds to get accurate exposure metering)

This is exactly the issue: 3 seconds is far, far too long - if you're shooting something alive auto-ettr unfortunately is out of the question, you need to capture the moment.

Some older sample shots here, it's w/o flash, but the sun was behind the people, thus the exposure difference was ~3ev just by pointing the lens in a bit different direction. I'd liked to ettr here for cleaner shadows (and would now use dual_iso) but I was wrestling with blown highlights because of the low dynamic range @high iso:

http://www.flickr.com/photos/83678576@N02/sets/72157631381779940/

I'd really like ettr to work in every situation and it's not your fault or something you could fix - but to be quick you simply have to use Canon's metering outside lv :-( ... however your latest additions to ettr are great and I'm keen to see where it ends up after being linked to autoexpo :->

3) shoot (no flash needed

Yes - it fills *all* shadows, but this often is not what you want. Flash is _not_ just for fixing exposure, but also for creativity and object/background separation - flash the object's shadows in the foreground while the background shadows stays natural and non-hdr'ish.

[a1ex]

For these quick situations you can try the "iso-less" mode: just set dual ISO to 100/800 or 100/1600 and forget about it (no more need for auto ISO, since it covers the entire range that sensor can do).

[Marsu42]

For these quick situations you can try the "iso-less" mode: just set dual ISO to 100/800 or 100/1600 and forget about it (no more need for auto ISO, since it covers the entire range that sensor can do).

I would have done that if dual_iso would have been available back then :-) ... however I didn't try cr2hdr enough to know if it leaves artifacts and how good denoising works at these large iso differences. Also for commercial photojournalism you often have to deliver the raw file, and they don't know about ml :->

[Audionut]

@Marsu42

Ok, you seemed to imply that autoISO was going to fix a number of exposure decisions.  I now see that you want (for the above example) autoISO, simply to limit the amount of changes needed over and above everything else that is being changed.

If you shoot outdoors in hard light (daylight w/o clouds)

Your ambient exposure decision does not change.  Well, at least it probably shouldn't when you have a flash exposure to compensate.

Can I suggest M mode.  Stay with me, the number of overall exposure changes will be lower.

Set your ambient exposure once.  Whether you are shooting into the sun, or away from the sun, the amount of light from the sun has remained constant.  I would suggest to set your ambient exposure on a scene away from the sun, with a shutter duration as long as possible while satisfying motion requirements.  This will give you some wiggle room (with shutter) for slight exposure reduction if needed/wanted when shooting into the sun.  This will take out the EC changes, as you no longer have to compensate for automatic metering.

ISO is set with the ambient exposure and left alone.

Your ambient exposure is now set and doesn't need to be changed unless a cloud comes over or you move to a scene in shade.

Flash in E-TTL should automatically fill in the shadows (shooting into the sun), and do almost nothing (shooting away from the sun).  I would suggest that you will probably need/want some amount of negative FEC in all situations.

You should now be shooting into a mode where no exposure changes are needed regardless of your shooting orientation.  And any changes that are still left to be made, should certainly be a considerable amount less then what you described above.

3) shoot (no flash needed, dual ISO and my color grading script will take care of the shadows)

Dual ISO removes the need for flash in almost all situations where flash is being used solely for shadow fill.

There's still something that I want to try for auto ETTR: link to auto expo module (so ETTR will provide an exposure compensation) or to Canon metering (for instant updates outside LV - though I'm not sure if this will actually help or will screw up everything).

EC control via AETTR would be very handy.  Take care not to apply negative EC though.  If people are shooting autoEXPO, their main concern is correct (18% recorded at 18%) exposure.  Automatic positive EC to ETTR would be handy, automatic negative EC to respect the white point would not.

If the white point could be found outside of LV, for automatic ETTR outside of LV in varying light conditions (3 seconds is much to long for a still shooter to wait where light is constantly changing), that would be all kinds of awesome.

[camera7]

Try how the auto-ISO works in EOS cameras with M-mode without flash. You set both fixed time and fixed aperture but get the right exposure in quick changing lighting conditions because the auto-ISO changes accordingly. This works perfectly fine without flash. You make the creative decisions and Canon takes care of the best exposure within the dynamic range. On the top of that you can add EC as you wish. No big deal. I'm happy :-)

As soon as you switch on the flash it is a different story. ETTL looks after the flash ratio very well, and you can compensate too. But the ISO refuses to change automatically. So I keep adjusting ISO manually all the time to get exactly what I want. And I do get it. The flash ratio and the compensations work fine in my EOS cameras regardless of the ISO.

The only problem is I have to do manually what could probably be easily automated. I have no experience on the Nikon cameras but someone said they are smarter here. This thread is about whether it is possible, through ML, unlock the fixed setting of ISO 400 when using flash? I'd like to see the auto-ISO setting behave identically with and without the flash. I'm asking because I don't know the answer?

[Marsu42]

This thread is about whether it is possible, through ML, unlock the fixed setting of ISO 400 when using flash? I'd like to see the auto-ISO setting behave identically with and without the flash. I'm asking because I don't know the answer?

For M what you asked isn't available, but I just added a feature request for the autoexpo module - feel free to +1 it or check if it is what you want: http://www.magiclantern.fm/forum/index.php?topic=7208.msg76187#msg76187

Dual ISO removes the need for flash in almost all situations where flash is being used solely for shadow fill.

Which is nearly 0% for me because I don't only use flash for shadow fill (it's more of a side effect except for very high dr) but for background separation, otherwise I'd have to do this in postprocessing for every single image. For me, a shot with a slight gelled flash on the subject looks much more professional, or at least "different" from the crowd...

... I would petition everyone not only to think about flash as a way to fix shadow problems, but for separation and shaping light in the scene - I hope sooner or later ml will be more up to date for flash shooting as right now the flash backend isn't reverse engineered enough (all the flash props).

I'll have to take more time to get into your other suggestions for shooting with M mode.