mark_scheuern

<P>Cryptographer and security expert Bruce Schneier has an interesting article about dealing with pointless, stupid security measures, "How to Fight", in the current <A HREF="http://www.counterpane.com/crypto-gram-0307.html">Crytpo-Gram</A>. Alas, you usually can't fight since the people who enforce security aren't the ones who make the rules, and the ones who make the rules often don't have a clue.</P>

Watts are a measure of power, which is the rate at which energy (measured in Joules) is used, so 1 watt is 1 joule per second. That is, if you had 1 Joule of energy stored up and released it through a flash for 1/100 second, the power would be 100 watts. Take that same amount of energy and use it up in 1/1000 second and it's 1000 watts.

 

Watt-seconds (note the dash, not the slash) is watts multiplied by seconds, which is the same as joules, so a watt-second is a measure of energy. Again in the example, 1 watt-second of energy (the same as 1 joule) used in 1/1000 second is 1000 watts. Using the example of tungsten, continuous lighting, a 100 watt light bulb turned on for 1 second uses 100 joules of energy. (100 watts is 100 joules/second, multiply that by 1 second and you get 100 joules).

 

So, in theory, a 100 watt light bulb used to make a 1 second exposure should deliever the same amount of light energy as a 100 watt-second flash. It doesn't really work out that way of course because the amount of electrical energy used doesn't translate directly into the amount of light delivered to the subject. It depends on the electrical efficiency of the light source (how much electrical energy actually gets converted into light in the visible spectrum), reflectors and other light modifiers, etc.

<P>Another point: I realize this isn't your department, but I'm more disturbed by this sort of thing: <A HREF="http://www.latimes.com/services/site/la-pr-000907a.story">LA Times to Host Second Annual Festival of Health</A> which features, among some no-doubt good things, talks on accupuncture, aromatherapy, and feng shui fundamentals. Now what is the scientific value in <EM>that</EM>? While I think your article on astronomical imaging could be quite interesting, expect to find people doing their jobs doing genuine science while at the same time trying to interest the public in science with some beautiful and by no means fraudulant images. I'm much happier seeing genuine scientific research promoted than pseudoscientific claptrap like the above and I hope you have or will turn your skeptical eye toward that sort of outright nonsense and fraud.</P>

<P>Joel Achenbach of the Washington Post discusses this at some length in his book <EM>Captured by Aliens</EM>. Like you say, it really is the nature of astrophotography that things like subject orientation, color, and contrast are arbitrary. The human eye responds to a limited range of wavelengths so "accurate" is somewhat arbitrary. Then you get effects like diffraction spikes that can make images look more interesting but again, it's hardly cheating, IMO.</P>

<P>Mark</P>

Works fine with my D100 with firmware version 2.

<P>Ellis, I just checked my copy of <EM>Galen Rowell's Inner Game of Outdoor Photography</EM> and, in the chapter "Getting the Most out of On-Camera Fill-Flash", he says:</P>

<P><BlOCKQUOTE>I shoot away at will in most situations by simply presetting a fixed -1.7 compensation for the fill ratio. Before I explain how to do this, take my word for it that the amount of compensation delivered by the computerized autobalancing systems on smart flashes is insufficient for nature photography. It may produce a brightly lit publicity portrait of Hillary and Bill standing in front of the White House, or a paparazzi shot of someone else coming out of the back of that house, but it will just as assuredly over-light that wonderful dead tree at a similar distance from the camera in front of a mountain.</BLOCKQUOTE></P>

<P>Which isn't of course to say that he has to be right, or that it works 100% of the time (which he goes on to say isn't the case), but, at least for me, it is a useful starting point and it does seem to be the best choice a good percentage of the time. Now I do a lot of motorsports photography and what I do a good deal of the time is rather close shots in really crappy mid-day lighting (pitlane headshot sorts of things) so I certainly don't discount what you say. But, for me, most of the time it fills in the shadows just the right amount without making it too obviously "flashed"</P>

<P>Mark</P>

Another way that works well is to set the flash to standard TTL mode(not 3D multisensor balanced fill TTL) and flash compensation to something like -1.7. You can adjust the value for subject matter and taste, but -1.7 is usually a good start. I'd also suggest aperture-priority mode and remember that the shutter speed won't drop below 1/60 unless you've got slow-sync flash mode selected. It also of course won't go above 1/180s since that's the highest sync speed on the D100 (which, combined with the lowest ISO setting of 200, makes fill flash in bright light a bit of a pain--really my only complaint about the D100).

 

Mark

I haven't used E200 so I can't answer your question, but just a quick comment on the previous post: while Provia 400F is certainly more grainy than an ISO 100 slide film, I find it very usable. It definitely looks better than Provia 100F pushed two stops, and negative film isn't really an alternative if you want to shoot chromes.

 

Mark

The lens is not removeable.

It's the same as with the SB28. It's the highest speed at which the shutter is open across the entire frame so it's a property of the shutter and not of the flash or how it's connected.

You can set quality and fine-tune (plus and minus adjustments) white balance from the shooting menu as well as with the dial. See the manual, pages 43-46 and 51-55.

Olympus Stylus Epic for us. Great little camera.

I've used the Lowepro belt system when doing motorsports photography and it's worked pretty well, overall. The weight is nicely distributed, it's easy to get at my gear and misc crap, and I especially like the Film Drop pouch for exposed film. Generally, I like to remove the pouches and gear contained within that I'm not using at any particular time and leave them in my car. The main problem with it is that I'm not very big and it gets to be a bit too much when I'm trying to carry everything and, during those rare moments when I wonder what people think of me, I think I might look a bit silly, too.

 

I've yet to find something that always works for me. Sometimes I use the Lowepro S&F system, sometimes my Domke bag, and I'm giving a backpack a try, too. All have their advantages and disadvantages.

The F6 is a great bag but a bit tight for my 80-200/2.8 AF-S. I'd suggest the F2.

 

Mark

Joe's right; I was being dumb. f/22.5 means halfway between f/22 and f/32, where halfway is defined as being 1.5 times the amount of light entering. You wouldn't know that I have a couple of physics degrees...

 

Mark

The f stop is the focal length divided by the aperture, so the aperture multiplied by the f stop gives you the focal length. In your example, 22*9.6mm = 211.2 mm (and 32 * 6.6 mm = 211.2 mm, 45*4.7 mm = 211.5--you'd of course expect the values to be identical or at least very close, and they are). Since the aperture is the focal length divided by the f stop, for f/22.5 you have 211.2 mm / 22.5 = 9.4 mm; for f/22.33 it's 211.2 mm / 22.33 = 9.5 mm, rounded-off.

 

Mark

Presumably Simon wants a digital camera because, as he said, the client needs fast turnaround. Given that, I'd take a look at the D100. I shoot motorsports and use the D100 (as well as film cameras) and I'm very pleased with it. AF is indeed slower than an F5, F100, the D1 cameras, etc., but I don't find it to be a problem since I usually manually focus my racing stuff anyway.

 

Mark

I've never seen anything like this on any of my D100 shots at any ISO setting. I'm also curious as to what settings and post-processing you might have used.

 

Mark

The metal foot and nice locking lever on the SB-80DX are significant improvements over the SB-28DX, in my opinion. I think the SB-50DX has those features as well.

"Literally"? I didn't know the Nikon HQ was afloat. The D10 seems to be a nice enough camera and a worthy D100 competitor (and should be--it's Canon's third try at it), but I imagine we'll be seeing some price cuts from Nikon. I just bought my D100 a couple of months ago but I'm not too upset. I've already gotten more than $500 of use out of it.

I can only say that I had my IIIf BD serviced (new shutter and a CLA) by DAG and he returned it, quicker than promised, in perfect working order. I thought it was well-worth the cost. You're happy with your local person's work on your SLRs and he says he can service your Leicas, and perhaps he can, but of course it's impossible to know without actually trying or maybe asking someone who's had work done on a similar camera. The number of really top-notch service people for these old cameras appears to be rather small.

Yep! Both are Arca-Swiss style.

Sounds like a more careful use of regular expressions is called for, at the least, and perhaps a re-think of policy.

 

This reminds me of the time my ex-boss called me into his office and asked me about "questionable" web sites I had been perusing at work. It turns out I had been flagged because I had downloaded the web server log analyzer "analog" and the URL contained the substring "anal".

The Nikon SC-17 cord will give you off-camera TTL flash with the SB-50.

Yes it can, Aaron.