andrew duncan

Every raw converter uses it's own algorithm to demosaic the image data from the Bayer filter. I would imagine that this is the source of the difference you are seeing. If you only want to use one channel for you forensic processing, a very simple demosaic algorithm may give the best results.<br>

Dave Coffin's <a href="http://cybercom.net/~dcoffin/dcraw/">dcraw</a> would be a good place to start.<br>

On another forum site I have seen some analysis of Canon's raw files that has used a software program caller <a href="http://www.astrosurf.com/buil/us/iris/iris.htm">IRIS</a>. This is used by astronmers and can natively read raw files.

Hope this helps,

Andrew

The hood made for the EF-S 17-55 f/2.8 is a good alternative for the EF 17-40 f/4.0 on APS-C body. It is the EW-83J. There is a comprehensive comparison <a href="http://www.burren.cx/photo/alternate_hoods.html">here</a>.

<p>If you search on EBAY for EW-83J you should be able to find a number of chinese copies of this hood that sell for around $US 15 including postage.

Andrew

Sorry Gil, now I understand your problem. I can see <i>My Computer</i> because I have it visible on the desktop. I don't have any other suggestions, I hope someone else does!

Andrew

Below the three tabs marked <i>Zoom mode</i>, <i>Scroll mode</i> and <i>Preview Mode</i> you will see a number of icons. One icon is a green arrow pointing up, it's tail is bent to the right. If you place your mouse over this icon you will see a <i>tool tip</i> saying <i>up</i> if you press this you will go up one directory at a time, until you should be able to see <i>My Computer</i> and the drives on your computer. I hope this helps

<br>

Andrew

Denis,

Another option would be to buy the White Lightning flash units. They are made by the same people as the Alien Bees, but are sold as pro level units. The <a href="http://www.white-lightning.com/flash2.html">white lightning X-1600</a> can be swithed to one quarter power, effectively making them an AB400 and AB1600 in one unit. I don't own either of these, but I came across this information on another forum.

<p>Hope this helps,

<p>Andrew

<p>"What is more for luminance hostos (on 20D etc) the camera bases this only on the magnitude of the green channel, although I am less sure of this point. Might be different for cameras that can display a RGB histo."

<p>This comes up every so often. It appears that many people are convinced that the 20D histogram uses only the green channel. I tested this on my own 20D and I am convinced that the 20D histogram is computed from a weighted sum of all three channel, with a considerable bias towards the green channel.

<p>In JPEG compression the first thing that happens to the image is that the RGB components are converted to another colour space called <a href="http://en.wikipedia.org/wiki/YCbCr">YCbCr</a>. Y the luma component is calculated as 0.299 * red + 0.587 * green + 0.114 * blue. IMO, it is possible that the 20D histogram is calculated from luma component of the JPEG thumbnail, or it could be calculated from some other weighted sum of red, green and blue.

Andrew

I would sell the EW-83H and get an EW-83E if I was you. There are plenty of people looking for the EW-83H to use with the 16-35mm or the 17-40mm on cameras with APS-C sensors. See <a href="http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=00Ergu">this</a> thread. The EW-83H goes for $55 at B&H, while the EW-83E is only $34. So swapping would probably cost you nothing (other than some time).

Andrew

Amy,

Enjoy your visit to Melbourne. I hope that you are going to see a few places in Victoria.

The Canon service centre in Melbourne is at 33 Lakeside Drive Burwood East. This is about 20 kilometers east of Melbourne city itself. I haven't had my sensor cleaned there, but I made enquiries last year. From my memory is cost around $AU 50 for a sensor clean. I'm not sure how quickly they can do it.

If (or when) you are in Australia, you could call their toll free number and enquire. 13 1383.

Hope this helps,

Andrew

Michael, I assume you are talking about the 216 'web safe' colours. These were important when most people had display adaptors with only 256 colours. I think we are well passed those days. However, the use of a web safe colour (or not safe) is not really the issue, but the implementation of PNG transparency in Internet Explorer.

Sorry Forrest, I don't have IE6 handy at the moment either, but I am pretty sure your effect won't look the way you want it to in IE6. I played around with this a few years ago (before IE7) and ended up using transparent GIFs and dithering the tranparent colour to simulate an alpha channel (yuck).

Hope this helps,

Andrew

Jerry, I think this is a better article about colour spaces at the Cambridge in Colour website.

<br><a href="http://www.cambridgeincolour.com/tutorials/sRGB-AdobeRGB1998.htm">sRGB vs. ADOBE RGB 1998</a>

<p>Andrew

I use a Canon 20D most of the time. I recently replaced our broken Canon PowerShot A70 with the PowerShot A630. It is the same as the A640 but has 8 megapixels rather than 10. When I bought the A70, it appeared a much better buy than it's brother the A60 (3.2 vs 2.0 MP), but I didn't see a big advantage between the A630 and the A640. To be honest, the A70 was a good enough camera for me, in terms of number of pixels.

One of the things that I love about the A630 is that it has flash exposure control. This really helps me when using the flash as a fill.

Andrew

I don't know the specifics of the Fuji raw format(s). If they already use some form of compression, then recompressing may not give you much (or any) reduction is size.

<p>If you are using ACR, you could convert your RAW files to <a href="http://www.adobe.com/products/dng/">Adobe's Digital Negative format (DNG)</a>. Using the options in the Adobe DNG converter for 'no JPEG preview' and 'lossless compression', the DNG file may be smaller than the Fuji raw file. You would need to experiment.

Abdul what camera are you using?

<p>Bob, according to <a href="http://www.canon.co.jp/Imaging/flashwork/lineup/index.html">Canon</a> the Off-Camera Shoe Adapter OA-2 is not compatible with any of the Canon DSLRs or the Rebel T2/300x. Is this correct?

Abdul,

Your choices are (in no particular order)

<ul>

<li>Buy a <a href="http://www.usa.canon.com/consumer/controller?act=ModelDetailAct&fcategoryid=141&modelid=8304">wireless transmitter</a>

<li>Buy a 550ex or 580ex to act as a master

<li>Chop your off camera cord in two and add some wire to it to make it <a href="http://photography-on-the.net/forum/showthread.php?t=117659">longer</a>

<li>An alterative, buy a cheap flash that has varying power settings and buy a cheap wireless transmitter/receiver from an online seller.

</ul>

Andrew

No officially, but there are DIY solutions such as <a href="http://burren.cx/photo/flash_power.html">this</a>.

<p>Andrew

Leopold,

That is the Bogen/Manfrotto 679 (3016) monopod that I was talking about. $42 from B&H if you are in the USA. The black one is the same price [bogen/Manfrotto 679B (3216)]. The 234 (Bogen 3232) head is $20, the 234RC (3229) is $31.

Andrew

The Manfrotto 3229 head that Steve is talking about, is the same as the Manfrotto 234RC head. It depends on what part of the world you are in. I think Manfrotto use the Bogen name in the USA and Manfrotto in the rest of the world.

Bogen 3229 tilt head is the same as the Manfrotto 234RC head

Bogen 3232 tilt head is the same as the Manfrotto 234 head

Andrew

Maria,

The <a href="http://www.manfrotto.com/Jahia/site/manfrotto/cache/off/pid/2366?livid=103|113&idx=115">Manfrotto 679 monopod</a> is a little lighter (and cheaper) than the <a href="http://www.manfrotto.com/Jahia/site/manfrotto/cache/off/pid/2370?livid=103|113&idx=115">681</a>, but extends to the same height. It is solid enough for a Rebel XT + 300mm lens.

I didn't go for a ball head. I have the <a href="http://www.manfrotto.com/Jahia/site/manfrotto/cache/off/pid/2375?livid=103|113&idx=114">Manfrotto 234 tilt head</a>. It is also available as with a quick release plate (<a href="http://www.manfrotto.com/Jahia/site/manfrotto/cache/off/pid/2376?livid=103|113&idx=114">234 RC</a>). I find the tilt head good for switching from horizontal to vertical shots.

Hope this helps,

Andrew

Ed,

I think that you are talking about a duotone (tritone, quadtone). To do this in CS2 make your image into an 8 bit grayscale image. Then choose image->mode->duotone... You can then select the two colours to replace black and white (for a duotone).

"it uses CR2 batteries, which are quite pricey to replace". That's true. I bought the battery grip with the camera. With the battery grip you can use 4xAA batteries instead of the CR2 battery.

Andrew

If they are going for the same price, the T2 is the next model up from the K2. Also the T2 is a (slightly) newer camera. I would go with the T2. I have the Ti (replaced by the T2) and it is a nice camera.

Andrew

Even uncompressed 2040 x 1530 pixels x 3 bytes per pixel only gives around 8.9 MB.

Andrew