joseph_pribe

Rob,

Most of the "confirmed" RFI examples I have viewed indicates RFI causes straight lines to appear. The OPs image has wavy lines. I was throwing a different idea out...regardless, since I have looked at this thread and poked around the net a bit concerning this issue with the 5D, I can now stop thinking about upgrading to the 5D from my 20D.

<p>notice the 5D is called out specifically...are you using a filter? have you tried a range of lenses?</p><p>

-JP</p>

<p>***from <a href="http://hannemyr.com/photo/defects.html" target=_blank>http://hannemyr.com/photo/defects.html</a>***</p>

<p>----snip---</p>

<p>Moiré</p>

<p>Moiré can be avoided by the use of a so-called anti-alias-filter on the digital sensor. This is an optical filter that cuts down the sampling frequency to half of the imager's sensel pitch, keeping it below the Nyquist frequency. But because an anti-alias filter also will make digital images appear softer and less sharp, some manufacturers choose to make cameras without, or with a weak anti-alias filter. Cameras without an anti-alias filter include the Kodak DCS Pro 14n and Sigma SD10, while the Nikon D1h and the Canon EOS 5D are cameras with a weak anti-alias filter.

<p>The image below, taken with a Canon EOS 5D, shows the effect of false colour moiré. It is typical of a Bayer sensor with a too weak anti-alias filter.

<p>----snip---<p>you'll have to hit the site to see the pic

<p>obligatory wiki article: <a href="http://en.wikipedia.org/wiki/Moir%C3%A9" target=_blank>http://en.wikipedia.org/wiki/Moire</a></p>

<p>While a few responses seem off the mark, many are close but don't seem to fully answer the question so here goes:</p>

<p>In your post, you seem to assume that PPI and DPI are interchangeable: this is not true...but they are related.</p>

<p> <a href="http://en.wikipedia.org/wiki/Pixels_per_inch" target=_blank>PPI is a measurement of the pixels in your monitor.</a> If you know the PPI of your monitor you can use it to determine at what size you should view an image on screen to see it actual size.</p>

<p> To make it easy, let's assume that your monitor has 100 pixels per inch. If you set the image to 100 DPI and set the image to display at 100%, you will see the image at actual size. To follow up on that, if you then print at 100 <a href="http://en.wikipedia.org/wiki/Dots_per_inch" target=_blank>DPI (refers to the dots per inch output of a printer)</a> and hold that hard copy up to the screen they will be the same size.</p>

<p>To make the most use of DPI, you need to know the dots per inch output of your monitor. Once you do, you can set your images to display at the right sizes (100% will really be 100%). As was mentioned however, the whole issue in relation to your screen (talking about dots per inch) is arbitrary if you already know how large you are going to print the image.

<p><a href="http://en.wikipedia.org/wiki/Dots_per_inch" target=_blank>DPI </a> as a function of printing your photos will vary depending on what you are doing. My 20D has a resolution of 3504 x 2336 pixels. So, if I wanted to print at 100 DPI, the output would be 35.04 inches by 23.36 inches. Once again, we typically don't decide to print in DPI, we print in inches.</p><p>I had one image I was putting into a show that I wanted to look nice from a good viewing distance (5-6 feet) and up close (it was a macro shot). To make sure those viewing the photo had the best of both worlds I decided to print at 300 DPI (generally accepted as the limit of human vision) so it would look good from 5 feet and from 5 inches. I printed the thing at 12 x 18 inches. </p><p>Doing the math again, printing the image at 300 DPI would have yielded an image much smaller than I wanted, so I had to increase the resolution of the image to ensure I had enough pixels to discern detail up close. </p><p>I hope this makes sense, the Wiki articles will help add some understanding.</p><p>So, who the hell wants to print an image at 72 PPI? No one...images are printed in DPI. Who would want a 72 DPI image? You might in a large print. There isn't any reason to print a 4 x 5 foot poster at a high resolution because it is viewed comfortable from 10 or 20 feet away...the detail is wasted(usually). More than likely, however, you won't need to worry about it unless you are going for a specific effect: the software will determine what the DPI will be based on the image's original resolution and the requested output size...again, as was previously posted, just tell the program how big you want the image, it will do the math and tell the printer how many DPI to print at.</p><p>A better question might be "Who wants to print at 1 DPI?" The answer to that might surprise you: outdoor ad agencies print those big billboards at somewhere around 1 DPI, even though the images are created on a monitor with 200 PPI (typical of an LCD monitor). Why? The 1 inch blocks (dots) blend together from the typical viewing distance of a few hundred feet. This is an extreme example but I hope it helps to clarify the differences between DPI and PPI.</p><p>Try out a program like the <a href="http://homokaasu.org/rasterbator/" target=_blank>Rasterbator</a> to have fun with DPI and to get an idea of how DPI can affect an image.</p><p>The other thing you can do is the modify the PPI of your computer to see how it affects the display. While it won't change the physical pixels per inch the monitor is capable of, is will alter the computer to display differently. A windows PC is typically set to somewhere around 96 PPI (depending on the monitor and the manufacturer)...changing that to a higher number makes everything smaller (more pixels per inch displayed) and changing the display's PPI to a lower number makes everything bigger (vice versa). Have fun experimenting: it seems to be the best way to get a real feel for how DPI and PPI interact.</p><p>I'll come back to this post later and toss on a follow-up in a few hours if I come back and it makes less sense later than it does now: DPI vs. PPI can be very confusing, especially when trying to explain it.</p><p>-JP</p>

There is a relatively inexpensive way to get a feel for the the print quality at the sizes you are thinking of. Print a small portion of the image at the expected zoom on a 4x6 photo sheet (WARNING: This step will require a bit of math! :) ). I do this to get a feel for both quality and color when I'm printing on my Canon i9900.

Remember one thing: people will instinctively stay back from large images; don't be disappointed with the test print if you can see pixels with the test section of the image when it is 18 inches from your face. Everything will blend together naturally at a normal viewing distance for the size print you are looking to make.

I print many images on 13x19 (or 13xwhatever if I'm using a roll) paper in my i9900 and always do a "snapshot" on a 4x6 of a region of the image I'm particularly worried about, whether I'm checking color output or detail in some region of the photo.

Hope this helps!

Kevin,

What you probably saw was the the Nikon version of the Canon "EOS Capture" utility. I use it on occasion with my 20D, it is really handy when doing a workshop or with studio work. I'm sure the software for the 5D is similar (a quick trip into your manual should help). Start the Canon software that came with the camera (in my case called Digital Photo Professional) and then you should find "EOS Capture" or similar within the menus. The utility works by allowing you to snap with the click of a mouse instead of the shutter button and displays the captured images directly on the computer, negating the need to download the photos separately.

A quick web search might land you here: http://software.canon-europe.com/software/0022674.asp?model=

-Joe

You can find dozens of FD-EOS adapters on eBay for $20-$30. I bought one from a guy in Hong Kong so I could attach my bellows and FD 130MM fixed lens to my EOS 20D. The macros are impressive...I simply unscrewed the optics in the adapter and the glass rides in the bottom of my bag should I ever need it. <br><br>results on my flickr account<br>

<a href=" target=_blank>lily pistol</a><br>

<a href=" target=_blank>lily petal</a><br>

<a href=" target=_blank>macro record (lp)</a><br>