I’m reading a book on underwater digital photography in which the author advises (and shows an example) that reducing the power setting on your strobe will actually result in sharper focus.  I still can’t get my head around this.  Can someone explain (in layman’s terms) why this is so?

Hi Masguy,

welcome to DIGIDEEP.com!

I doubt what the guy wrote makes sense, the way I currently
read it. The only thing this may influence might be the reduction
of backscatter. Can you cite the exact text here to avoid any
misunderstandings?

Andreas,

Thanks for the quick response.  My source is “The Master Guide For Underwater Digital Photography” by Jack and Sue Drafahl (Amherst Media, 2005). On page 64 of that book, the authors state:

“At full power, most flash units are at 1/1,000 to 1/1,500 second.  If you use one of the reduced-power methods mentioned above, the flash duration could be as high as 1/12,000 second when at 1/16 power.  This increase in speed will result in a sharper image, especially when shooting at extreme macro magnifications.”

There it is.  They don’t say why this is, but they do have a picture comparison that seems to prove their point - it still makes my brain hurt trying to figure this out.

Okay, let me try to follow their thoughts…

Often considered is how much light a flash can deliver in a certain amount of time.

Large studio flashguns, such as Bron etc. are very costly due to this fact. With an
underwater strobe however you cannot have large external generators with you.
So they are limited to usually one condenser which delivers a certain amount
of Milliwatts in a certain period of time that takes much longer to deliver all
all the required stored in it.

Summing it up underwater strobes have to compensate lack of power
in a very short time by an extended burn-time (in some cases).

From what I understand their suggestion is to not use your strobe at the
full power. In return for not pushing it to the limit the strobe will deliver the
selected amount of light in a shorter period of time. According to their
advice this can can avoid unwanted strobe halo effects.

I have enclosed an example where I played with that effect on purpose to
have the picture more dynamic. Does that correspond to the example of
un-sharpness illustrated in your book? If that is yes, we might have
solved the issue.

HOWEVER: According to my practical experience this is really a lesser
issue and more dominating is the factor of the selected shutter speed on your
camera. If you select a slow shutter you will still get an unsharp halo effect,
independent of the strobe power you selected.

FURTHERMORE: Reduced strobe power will force you to select a smaller
aperture value, resulting in less depth of field. Especially in macro this is
a much more critical factor than strobe halos.

I am interested in reading your reply and have other experts chiming in.

I wrote the book’s author and he was kind enough to respond.  Here’s what he had to say:

First the technique comes from the field of scientific photography.  I learned it at Brooks Institute of Photography in 1968.  It works much like shutter speeds.  As you increase shutter speeds from 1/1000 second to 1/2000 and then 1/4000, the images become sharper because the time the image is on the sensor is shorter and there is less movement of the subject.  The same is with flash, assuming that the background light (sunlight) is so low that it has no effect on the exposure (very dark or black).  This is most common with macro images, where the sunlight is non-existent in the image.  Since the only light striking the sensor is the light from the flash, the duration is much like a shutter speed.  At full power it would be 1/1500 second, at half power 1/3000 second, and at 1/4 power 1/6000 second.  Shooting at 1/4 has a very short duration where the light is striking the subject, and is therefore sharper than at full power.  Not much but just a little.  This technique is popular with nature photographers that shoot macro topside.  They use large flash systems, and then use reduced power to keep their super macro images sharp.

Hope this helps
Jack Drafahl

Goes in-line with what I wrote above, but has some
practical limits if you do not buy top-nodge equipment.

More practical: If you select your strobes you should
also take a look at the MWs-Value which is more
handy than the strobes guide number.

Jack & Sue are a nice couple, we met them at the
Curacao Dive Festival this year, were they gave a
Photoshop lecture for U/W-photographers.

Anyway, I still would like to know if the effect on your
illustration looks similar to what I posted above.

I only see one picture.  In the book, there were too macro shots of the same critter with different flash settings the difference was significant.

The problem what I see with this, although it is technically correct is
the flash synchronisation speed, with most cameras and flashes.
In most cases the sync speed is somewhat around 1/200 or 1/250
second. With the system flashes some newer digital slr cameras
support high sync flash synchronisation, but I dont know of any
underwater strobe that is able to sync at high speed.

Here is another article on high flash sync speed:
http://www.rpphoto.com/howto/view.asp?articleID=1026

/lars

@Lars: the problem to sync at high shutter speeds is
also related to the camera and not only the strobe.

I know, for example the 1/200 is the common limit,
but the Canon EOS 20D can X-Sync at 1/250, too.

You have to look up the X-Sync with the camera
or try it with a surface eTTL/iTTL strobe in manual
mode on your camera. If you put the camera
at lets say 1/1000 and you turn power on the
flash connected to the hot-shoe the camera will
automatically cycle down to 1/200 or 1/250.

Try it

This is an interesting thread… because I recently changed strobes for a different reason, but found the result your article talks about.

And I’m going to counter Andreas’ comment about practical limits with less than top notch equipment, and say that I have found the opposite… those limits actually make this MORE important with less than top notch equipment. 

If you have a high end DSLR with nice macro lens, you have a great deal of control in getting the shot you want.  You can set shutter speed, aperture and between those you are almost certain to get a workable combination.

But if you are using a point and shoot, more than likely you don’t have control over both shutter and aperture, you get one or the other, or on some cameras, neither - its all automatic.  On top of that, you have a very limited aperture range, most point and shoots go from maybe 3.0 to around 9.0, unlike specialized lenses on DSLRs which can go from 1.2 all the way to 22.  Add to this that point and shoots suffer badly from shutter lag; uncertain timing combined with inability to set shutter speed means camera movement is a bigger issue.

This means that, particularly in macro situations with low ambient light, you are frequently overexposed and image sharpness is drastically reduced.

Now, for me, overexposure was my initial reason for changing.  I was using a DS-50 which has no power settings, and even with TTL, my macro shots were overexposed more often than not.  I started using a YS-110 so I could reduce the power.  But I found that not only did I get better exposures, my image sharpness increased as well.  Your article makes the best explanation I have seen yet.  In an environment where everything is in motion, where exposure control is limited and the dominant control factor is the strobe, less is more.

RG

Sorry GlassGoby, but I cannot follow your brainwaves…

How does this fit together?

GlassGoby - 17 August 2007 12:02 AM

...practical limits with less than top notch equipment, and say that I have found the opposite… those limits actually make this MORE important with less than top notch equipment. 

..versus..

GlassGoby - 17 August 2007 12:02 AM

I was using a DS-50 which has no power settings

I would state that this is the hardest version of a practical limit, I can imagine.
The Author (Jack Drafahl) states that you have to cycle down strobe power to
get a sharper image. You say than that it is even more important to do that
with a strobe where you were not able to change the power setting? 

Also,..

GlassGoby - 17 August 2007 12:02 AM

In an environment where everything is in motion, where exposure control is limited and the dominant control factor is the strobe, less is more.

I think this assumption is wrong. Assuming you have a compact camera in P mode only, as
you mentioned above. Correcting the strobe TTL signal towards minus would actually result
in an even more blurred/flawed image. The camera then assumes it will receive less light
from the dominant light source (strobe) it will select a shutter speed that is even slower
to compensate that. Hence the image will get blurry.

So I conclude “less is more” cannot be applied to this case.

I think explaining the failure of TTL with your old system with this very specific
photographic tip of Jack Drafahl (cited above) is misleading. Obviously the digital
TTL did not work or was not utilized roperly. In some cases (backlight or not
enough subject filling the frame) it fails to “heal” the image.

Also I think one of my statements was misleading:

Goes in-line with what I wrote above, but has some
practical limits if you do not buy top-nodge equipment.

With the top-nodge equipment in that quote I did not mean that
anybody should get a more decent camera to make that work.
I actually intended to refer to buying a strobe that is

A.) Capable of selecting manual power-levels ..and..

B.) .. is able to deliver enough light at half power setting
to allow you shooting the desired aperture in macro that you
want. Most strobes will fail to fully light a macro image taken
at IS0 100, Shutter 1/200, Aperture 16 till 32 - which I
consider as a common macro setting in most SLR shots.

Also be careful with the following:

when at 1/16 power.

..will not have the same output and burntime on every strobe.
It will vary as every strobe manufacturer makes it’s own scale
compared to the maximum light output the strobe has. So 1/16
is not the same on Hartenberger, Subtronic, Ikelite, Sea & Sea
or INON strobe. It will vary even with the model you selected.

Hope this helped to clean-up some mis-interpretations.

Andi

Andreas Voeltz - 17 August 2007 02:15 AM

Sorry GlassGoby, but I cannot follow your brainwaves…

Don’t worry, often, neither can I…

Andreas Voeltz - 17 August 2007 02:15 AM

I would state that this is the hardest version of a practical limit, I can imagine.
The Author (Jack Drafahl) states that you have to cycle down strobe power to
get a sharper image. You say than that it is even more important to do that
with a strobe where you were not able to change the power setting? 

No, you misunderstood my whole post.  That’s why I switched.  Because I couldn’t do it with the DS-50.  But it works great with the YS-110.  The limits I was talking about are the camera and lens (limited control).

Andreas Voeltz - 17 August 2007 02:15 AM

Assuming you have a compact camera in P mode only, as
you mentioned above. Correcting the strobe TTL signal towards minus would actually result
in an even more blurred/flawed image. The camera then assumes it will receive less light
from the dominant light source (strobe) it will select a shutter speed that is even slower
to compensate that. Hence the image will get blurry.

Yes, exactly.  The DS-50 I could only use with TTL and it wasn’t working.  Besides the blurring you mention, it was always overexposed.  And what you describe is even worse when you factor in shutter lag, since you don’t know when the picture will be taken (especially horrible in surge… which I get a lot of here in the cold northwest USA). 

Andreas Voeltz - 17 August 2007 02:15 AM

I think explaining the failure of TTL with your old system with this very specific
photographic tip of Jack Drafahl (cited above) is misleading. Obviously the digital
TTL did not work or was not utilized roperly. In some cases (backlight or not
enough subject filling the frame) it fails to “heal” the image.

I wasn’t explaining the failure of the DS-50, just the opposite, I was saying it explained the vast improvement with the YS-110. 

I can only use the DS-50 with TTL because without it, the flash is at full power all the time. The TTL is working, but it only works well when there is distance to the subject. In macro mode, where little flaws are much more glaring, it didn’t work well at all. 

With the YS-110 I don’t use TTL at all (with the Ikelite housing TTL only works with Ikelite strobe).  For macro I use aperture priority and set the aperture to 8.7 (as far as it will go in macro), with the strobe on lowest power.  I only up the power if I can’t get a decent exposure.

Andreas Voeltz - 17 August 2007 02:15 AM

Also I think one of my statements was misleading:

With the top-nodge equipment in that quote I did not mean that
anybody should get a more decent camera to make that work.
I actually intended to refer to buying a strobe that is

A.) Capable of selecting manual power-levels ..and..

B.) .. is able to deliver enough light at half power setting
to allow you shooting the desired aperture in macro that you
want. Most strobes will fail to fully light a macro image taken
at IS0 100, Shutter 1/200, Aperture 16 till 32 - which I
consider as a common macro setting in most SLR shots.

Well, we are talking opposite then, but saying same thing… when I said top notch equipment I meant the camera, not the strobe (DSLR, as opposed to point and shoot).  So same thing because what I meant was that if you have a less than top notch camera, that’s all the more reason to get a better strobe.  Most particularly for your (A).  Your (B) though hits exactly the limitation I was talking about, since point and shoots don’t have an Aperture 16.

Andreas Voeltz - 17 August 2007 02:15 AM

Also be careful with the following:

when at 1/16 power.

..will not have the same output and burntime on every strobe.
It will vary as every strobe manufacturer makes it’s own scale
compared to the maximum light output the strobe has. So 1/16
is not the same on Hartenberger, Subtronic, Ikelite, Sea & Sea
or INON strobe. It will vary even with the model you selected.

Yes, I am aware of that, not to mention battery recycling which can change power from shot to shot… but as Mr. Drafahl points out, in most circumstances, lower power also means shorter flash burst, and that can mean sharper image.

So to recap, I switched from the DS-50 to the YS-110 initially to get rid of overexposure problem of TTL.  After shooting with YS-110 though, I noticed not only better exposure, but also sharper images.  And the sharpness seems happen regardless of shutter speed.  I think his article provides a reasonable explanation why.

I would say anyone shooting macro on a point and shoot camera should explore getting out of automatic mode and using lower power on the strobe.  I can sure see the difference on mine.

Hi GlassGoby,

now I can follow your brainwaves and recommendation

To put it in one word, as compact cameras are
more light sensitive it makes also sense to buy
a strobe with manual control steps to take
advantage of this tip by Jack Drafahl, right?

However the fact that the author generalizes 1/16
strobe setting and that shutter speed is a much
more dominant factor than strobe sync speed
keeps me very still very sceptic and I would not
base my underwater photography decisions on that.

@masguy: are you still with us?

I will be in Borneo (Sipadan Water Village) next week and I’m going to try doing some comparison shots to test this theory out in the field (I have an Oly 7070 and dual Ike 125’s). I’ve attached one of my favorite shots taken at Wakatobi last year.