timarmes

Hello,

A flash meter tells you the aperture you'll need, at the current flash power, to correcly expose a mid-grey subject that's at the same position as the subject.

As an alternive to altering the aperture, you can change the flash power.

1) First, select a sensible flash compatible shutter speed such as 1/160.

2) Next, select the desired aperture that will give you the DOF you require.

3) Set you're flash to an arbitary power setting. Maybe 1/2 power. Take a flash meter reading.

4) If the require aperture bigger than you're using (smaller number), then increase the flash power. If the required aperture is smaller, then reduce the flash power.

5) Repeat 3) and 4) until the flash power gives you the desired aperture.

Tim

Hi,

I'm trying to find a hot shoe adapter to allow me to trigger a 580EX using a

radio trigger.

If I were in the US, then there wouldn't be problem, since B+H have them, and

paramount cords apparently make them too. However, I'm in France, and I don't

want to import from the US. Does anyone know where I can buy such an adapter

from in Europe (ideally France or the UK).

Ideally, the adapter would be designed so that it could itself me mounted on a

hot shoe or a tripod, and it would have a 1/8 jack socket to plug the triggering

unit into.

Thanks,

Tim

Thanks everyone for your responses.

I also asked this question on the OPF forums. It seems that the general consensus is the same: ETTL can be great for quick and simple lighting, or for constantly changing environments. For "staged" work manual off camera flash offers the greatest consistancy and creative control, which isn't surprising.

Perhaps for the moment the most flexible (and expensive) solutions is a Canon master and slave combo, giving you ETTL when you need "quick and simple", and manual with remote control of slaves when you want more control. At a later stage it's also possible to use a radio system to trigger the flashes (without any ability to control the settings) under arrangements where optical transmissions doesn't work.

Now I need to decide if that's an investment I'm prepared to make...

Regards,

Tim

Hi,

<p>

I'm really in need of some advice before I spend money on something that I'll

regret.

<p>

I currently do a fair bit of home-based "studio" work using a pair of Bowans

Gemini Esprit 500s. I therefore understand about using manual, off camera flash.

<p>

Now I'd like to invest in a lightweight portable flash for location work, and

this is where I'm stuck. By "location work", I really mean quick portraits and

general low-light photography. For anything more serious I'll probably just take

along my studio strobes.

<p>

One option is to buy the Canon 580EX. I've never used ETTL (other than the

next-to-useless on camera flash), but I think I nevertheless have a good

technical understanding of the principles behind it thanks to the numerous

articles out there (Photonotes, Doug Kerr's wireless guide, etc.). There are

things that I like the idea of:

<ul>

<li>Easy on-camera fill flash.

<li>Remote control of off-camera flashes via an on-camera controller such as

another 580EX or ST-E2.

<li>Automatic ratio control.

</ul>

However I have concerns:

<p>

<ul>

<li>Wireless control is done optically, and it would seem that this isn't great

in daylight, especially if the flash is behind me.

<li>Going radio isn't an option if you want to keep ETTL functionality

</ul>

<p>

Next-up, I'm using a 30D; is ETTL II really a decent system, or would I be

better off turning the flashes to manual mode? If I go fully manual, then I have

to consider:

<p>

<ul>

<li>Is there any point is buying a 580EX? There are much cheaper alternative if

ETTL isn't a requirement. Would the ETTL still be useful from time to time?

<li>In fact, should I buy a Canon flash at all? Since they don't even have a PC

socket (ridiculous), making them more awkward to connect to a wireless-by-radio

system.

</ul>

<p>

There are various sites that offer superb lighting advice. <a

href="http://www.planetneil.com/faq/flash-techniques.html">Neil van Niekerk</a>

makes out-standing use of on-camera flash and ETTL. On the other hand, <a

href="http://www.dg28.com/index.html">Neil Turner</a>, whos images I also

appreciate, uses off camera flash for most things. <a

href="http://strobist.blogspot.com/">David Hobby</a> is an avid advocate of the

off-camera cheap flash with pocket wizards approach.

<p>

The problem is that without having enough on-location flash experience I find it

very difficult to decide on the best way to go. I also don't have any experience

with ETTL to know if I trust it, although if it works I'd be happy with it,

obviously. Is the wireless-by-optical limiting?

<p>

I like Niel van Niekerk's approach of bouncing the on-camera strobe as much as

possible, and this is great for the photographer who needs to move with his

subject. On the other hand, for static subjects, the point mady by David Hobby

is a good one - that off-camera strobes give a good lighting consistancy and

allow the photographer more freedom of movement without having to constantly

change the flash position. I can therefore see myself doing both depending on

the circumstances.

<p>

I suppose the ideal solution is a 580EX with pocket wizards, which would also

allow me to use my pocket wizards on my studio strobes, however I can't afford

that approach. The ideal ideal would be that Canon introduce a radio based ETTL

system, and it rather concerns me that they'll do that just <b>after</b> I buy

the kit!

<p>

So, that all said, I'd really appreciate hearing your experiences on on-camera

vs off-camera and ETTL vs manual. Maybe you'll give me some things to think

about that I haven't already considered.

<p>

Thanks,

<p>

Tim

<p>Hi,

<p>Your question's been answered, but I'm not sure that it's been answered clearly, and this is shown by your response:

<p><quote>"I have seen people, on deciding which is a good portrait lens to get, *factor in 1.6 crop. If you choose a 100mm lens to flatten the image, why should the crop factor matter? You are choosing the portrait lens for its perspective are you not?"</quote>

<p>You haven't understood. To answer your question:

<p>

<ol>

<li> Perspective is determined by subject distance, not the lens used.

<li> An 80mm lens is typically used in 35mm portrait photography since the subject/camera distance for head-shot framing that the 80mm imposes creates a pleasing amount of perspective (features aren't disorted yet they're not too compressed either)

<li> To retain this same distance, and thus perspective, with a 1.6 crop factor, you'll need to use a 50mm lens.

</ol>

<p>Tim

I believe that the Save For Web option does 2 things:

1) It converts the image to sRGB

2) It removes any embedded profile, since they're never used by browsers.

Tim

Hi Jonathon,

Thanks for your detailed example. The advantages are now beginning to fall into place in my head. I now see the advantage is the absolute precision that you have over the ratios. The obvious disadvantage is the extra time (flash each light at each location of importance) and mental arithmetic involved.

Up till now you suggested using the meter to find the overall exposure once the lights have been set up. I'm still not sure how you go about setting up the power of each light easily if you are ailing for a particular DOF. For example, suppose that you decide that you need f/8, and you want a 3:1.

Can you explain the mental arithmatic you go through to do this please? What values do you metering to to get the desired effect.

Thanks again,

Tim

Thank you. A good point.

Effectively I see that in a complicated lighting situation you'd be better off measuring each light at each important point to find out the total eV values for the highlight/shadow area.

In the case of a simple set up with one key light and one fill, it's possibly quicker and easier to flash all the lights. However in this case both mothods will work and personal preference takes precidence.

Would you agree?

Tim

Oh, I forgot to add something. My thought process is like this:

For this subject, fX will give the desired DOF

Set up lighting

Expose brighter side to give desired fstop

This works because I'm alreading exposing for the total amount of light hitting the subject (key + fill). If I'm only measuring one light at a time then I can't do this.

Tim

Thanks for your responses.

Unfortunately, you haven't managed to answer my question :)

I completely understand the technique of measuring each light one at a time and then taking an overall exposure. It's logical, I can see why it works.

But why would that be better or more advantageous than measuring the ratios by flashing all the lights and pointing the meter at the camera? In doing this, you're taking into account the total light hitting the brighter side (key + fill) verses the fill only side. Should you decide for whatever reason not to have even fill, then it's taken into account.

Thanks,

Tim

Hi,

I'm sorry, can you explain what you mean in more detail.

I don't understand why measuring one light at a time would be more accurate than reading all the lights, thereby assuring that you mesure what actually falls on an object.

There seems to me to be lots of room for error in the second method.

Thanks,

Tim

Hi all,

I have a question concerning the use of a flash meter to determine

lighting ratios.

Currently, I use the flash meter by positioning it at the subjet and

pointing it at the camera. I do this for both the lit and filled

areas of the subject, and adjust the power/position of the lights so

as to give me the desired f-stop value for the main light and the

desired ratio between the hightlight and shadowed areas. When using

the flash meter I flash ALL the lights, so that they are all taken

into account.

I've just read about another technique which involves the following:

Place the light meter at the subject position.

For each light, flash ONLY that light with the meter facing the

light, so as to get its incident reading.

Adjust the power of the lights to get the ratios desired.

Place the meter at the front of the suject and flash all the lights

to get the overall exposure setting for the camera.

When calculating the ratios like this you must take into account the

overlap of the flashes. For example, assuming that you want a 2:1

ratio, with a key light to the left of a subject and a fill light at

the camera position, the fill light will light both side of a face

evenly, whereas the key light will only light the left. With both

flashes at the same power, the left will therefore be 2 times brigher

than the right (since both flashes are lighting it). When checking

your rations, you need to consider this in advance and ensure that

both incidence readings give the SAME reading.

The second method seems more complicated to me. However, there are

people who use it, so I assume that it must offer some advantages.

So, my question is, what are the advantages of each method?

Thanks,

Tim

Not yet. I've just ordered what I <i>think</i> is a Minimagick from ebay:

<p>

<a href="http://cgi.ebay.co.uk/Brand-New-Radio-Wireless-Trigger-for-Studio-Flash-Unit_W0QQitemZ7567606814QQcategoryZ3860QQrdZ1QQcmdZViewItem">http://cgi.ebay.co.uk/Brand-New-Radio-Wireless-Trigger-for-Studio-Flash-Unit_W0QQitemZ7567606814QQcategoryZ3860QQrdZ1QQcmdZViewItem</a>

<p>

It certainly looks identical, although the actual make isn't mentioned. For 20UKP including delivery, I figurered that I couldn't go too far wrong.

<p>

Tim

Hi,

I have an idea for a photo that I'd like to take that involves a

closeup of a 1/4 face with an important reflection in the glasses of

the model. Part of the reflection will be that of an illuminated

monitor.

Normally, for a monitor, you can combine flash exposure with the

ambient light from the monitor. In this case however, the slow

exposure needed for the monitor would cause a problem (since it's

projected onto the model).

Any ideas?

Thanks,

Tim

Hi all,

I'm currently investing in some home studio equipment. I decided to

go with the Bowens Gemini Esprit 500/500 kit as a staring point.

Since that's my entire photgraphic budget blown for the year, I need

to find a source of sensibly priced 3rd-party accessories. The

Bowens accessories are ludicrously priced - for example, who on Earth

wants to pay ?150 for a set of barn doors, or ?90 for a simple gel

filter holder? Not many amateurs, I'd wager.

I notice that the Interfit accessories use the S-Type fitting, and

are considerably cheaper. Do they all fit seamlessly on the Bowens

without any problem?

Are there any other suppliers that are even better value. I realise

that there is a big difference in quality between, for example,

various softboxes, but for things like filter holders and barn doors

I'm sure than my home studio will cope quite well with a cheap

solution. Cheap gels would be nice too

Note that I'm based in France, so I'd rather find either european

based supplier (probably UK based, since the competitive economy

brings the best deals).

Thanks for you advice,

Tim

Hi David,

Yes, it's possible. Just use the "Convert to Profile" command (Image menu, I think).

Better still, ask your local lab to use the embedded profile (AdobeRGB) for colour conversion.

Tim

Thank you all for your answers. I now understand from you answers and posted links that the incidence meter effectively acts as a neutral grey subject. You face it towards the camera (and NOT the ligt source and someone else suggested) and it essential tells you the exposition that would be needed to expose a neutral grey subject at that point as a neutral grey subject on the film. With the exposure set, all other objects shoould fall into place - white will be white, black will be black, etc. By facing it at the camera you're considering the light that would be reflected back to the camera from the subject. It's all very simple when the principles are explained.

That all said, the other questions that I posed regarding the studio lighting on a budget link still don't make much sense to me.

I now understand why the incidence reading should be the same for the foreground and background, but I still don't think that you should aim for the same readings when using a reflected light meter.

And I'm still confused by his "very best" method of using an incidence reading on the subject and a reflectance reading on the background. He doesn't actually explain what he's aiming for with each reading (same value or 2.5stops difference)

Thanks,

Tim

Hi,

Thanks for your responses. I'm so used to the idea of compensating for a reflective meter bases on the subject that I grasped the fact that you don't need to compensate for an incidence meter, good point.

Now, how does that work, exactly? The meter knows exactly how much light is needed to produce a correct exposure for a given ISO, and returns a suggested aperture/shutter speed to expose a 18% subject being subjected to the given amount of light?

Hi all,

I hoping that someone here will be able to explain something to me

that's been playing on my mind for a while - the difference in usage

between incident and reflacted light meters.

I understand that an incidence meter mesures the amount of light

falling on a subject, whereas the reflected light meter meters the

amount of light being reflected back off the subject, but I don't

understand the following:

1) How is the incident meter useful? The reflected light from a

metal sheet will be far higher than that off black cloth, even if the

light source is the same. Since the incident meter knows nothing of

the material, how can it possible give you an exposure level for the

object?

2) Why so you have to face the indicence meter at the camera rather

than the source when taking a reading?

3) When would you use one type of meter over the other? Why?

I ask you to read this article:

http://www.ephotozine.com/techniques/viewtechnique.cfm?recid=195

Now, the author says:

"... what you want is a situation where the background is 2.5 f/stops

brighter than the subject. If your meter will allow you to do this,

the very best way is to take a reflected light reading of the

background and an incident reading of the subject. The reason for

this is that the reflected reading takes into account the colour of

the background while the incident reading of the subject is

independent of colour and reflectivity."

What does the colour of the subject matter when calculating the

exposure? How does this achieve the 2.5stop difference? I don't get

that at all. He goes on to explain:

"...if your meter does not allow you to take reflected light

readings, use it in incident mode, both at the background position

and at the subject position and adjust diffuser and light until you

get the same reading at both positions."

Same reading? How will this achieve the 2.5stop difference?

"...If you can only take reflected readings use the meter directly at

the background, onto an 18 percent grey card at the subject position

and aim for the same reading at each position. Starting with a white

(ish) background, you will now have a true white background for your

images."

I'm still lost. The background meters x eV to be rendered 18% grey.

The grey card also needs x eV to be rendered 18% grey. Take the

photo - grey card against grey background. What am I missing?

Thanks for you help,

Tim

The nicest way is to use the Channel Mixer.

Create a new Channel Mixer layer adjustment layer. Click monochrome. Use 100% Red and 0% for the other two layers.

Alternatively, use various quantities of the three layers to change the monochrome effect.

Tim

Michael,

The link in question doesn't discuss this. However, his book, the INS and OUTs of FOCUS does (available by PDF if you follow some links from the link in question).

It really depends what the origianl poster is asking. I'd asumed that he was talking about the DOF scales on lenses, but I conceed that this may not be the case.

At several points the book above mentions the discrepency between the distances as mesured from the lens from nodal point and those marked on the lens. For example:

"One more correction: remember the distances we have been working in are measured from the front of the lens whereas the standard distances shown on camera lenses are measured from the film."

So, it all depands on what you're using.

Tim

They are actually measured from the film plane.

The link that Neil posted needs to be read...

Tim

Hi Skeeta,

I was being purposely vague so that people would read the referenced sites - Mister Merklinger explains it all so well.

Essentially, he turns DOF on its head. He noticed that the concept of the circle of confusion isn't always very useful. What the circle of confusion tells us about the use of the hyperfocal distance, for example, doesn't actually translate very well in practice. Indeed, the circle of confusion disassociates the scene being protographed from the impression of sharpness - he explains his reservation on this approach.

Harold noticed that focusing at infinity produced far better results than focusing at half the hyperfocal distance. He also discovered that photos containing distinct images that looked truly sharp were displaying circles of confusion of arount 1/200mm - much smaller than the 1/30mm that we use today. (He explains why he thinks this value is non-sensicle)

However, using a 1/200mm circle of confusion and pluging that into the DOF equations suggests that the DOF would be practically zero, and that clearly wasn't the case. The circle of confusion is simple not useful in estimating image sharpness.

In turning DOF around and considering the actual size of the smallest objects that you want to resolve, he demonstrates why the tradional approach to DOF is poor, and presents a method that's truly useful.

I'll let you read the links above.

Tim

Hi,

<p>

I used to use DOF markings. I no longer find them useful.

<br>

I used to use tables. I found them long, complicated and ultimately not useful.

<p>

I understood the concepts of DOF, of the circle of confusion, of the effect or film/sensor size, etc. It all makes sense, it's logical, and yet in reality it never seems to work all that well.

<p>

What I expected to be sharp, wasn't really as sharp as I wanted, and the results weren't what I expected.

<p>

Fortunately I wasn't the only one to notice this. Someone much cleverer than me noticed it too, and about 15 years ago he wrote various articles and even a book on a new way of thinking about depth of field, based on first principles. His method is quick and easy (although not as quick as DOF marks, it has to be admitted), and more importantly it really does put the photographer in control of level of sharpness he or she needs in a particular situation.

<p>

I now understand than when I use DOF marks, I'm setting a minimum level of acceptable focus that is actually based on some really very bad assumptions. I now understand that focusing at the Hyperfocal distance will give me backgrounds that aren't very sharp at all - acceptably sharp? Not to my eyes.

<p>

Now, when I stand in front of a scene and DOF is important, I considered the DOF that I want, and the level of sharpness that I need. Do I need to resolve pebbles? Hair? Distant window frames? Do I want to ensure than certain objects are thrown well out of focus, or do I want everything to be as sharp as possible? I consider the physical size of the objects in question, and then I choose the appropriate f-stop and focus point.

<p>

Taking your example, I would think like about it like this:

<p>

A 50mm lens at f4 gives me about an aperture of about 12mm (actually 12.5).

<br>

I want to resolve object at least .5mm - freckles. .5mm is 1/24 of of aperture diameter.

<br>

This means that the DOF for my chosen minimum resolution size will be 1/24 of the distance to the object, each side of the object.

<br>

5m * 1/24 is appox 20cm. My DOF is from 4.8m to 5.2m. Focus on the eyes and I'll resolve freckles that are 20cm away (and they're much nearer than than, obviously).

<p>

All that, and the format size isn't even taken into account. How can that be?

<p>

Here's a very good overview. It's worth reading it carefully a few times to let it sink it. You may never turn back - I haven't.

<p>

<a href="http://www.trenholm.org/hmmerk/DOFR.html">http://www.trenholm.org/hmmerk/DOFR.html</a>

<p>

Here's are 4 articles covering the subject in more depth:

<p>

<a href="http://www.trenholm.org/hmmerk/HMbook14.html">http://www.trenholm.org/hmmerk/HMbook14.html</a>

<p>

Here's the book itself, probably too in depth for most, as a PDF:

<p>

<a href="http://www.trenholm.org/hmmerk/index.html#TIAOOF">http://www.trenholm.org/hmmerk/index.html#TIAOOF</a>

<p>

Enjoy,

<p>

Tim

Hi all,

Thanks for your answers. Alan, your answer was particularly helpful to me, however I'm still not quite there...

When I draw out the situation you describe, with effectively two similar triangles, and it seems to me that the light that diffracts as it passes through the aperture at 200mm will have spread out further from the focus point than the light that deffracts at the 22mm mark, because it has further to travel before hitting the film. I would therefore expect more deffraction from the 200mm lens.

What am I missing?

Tim