steve_maslin1 Posted August 21, 2003 Share Posted August 21, 2003 I am thinking about getting the Canon G5, I would like to know about the purple �fringing�.. is there a way you get arround this? would the ND filter setting work ? And how much of it is a problem? My other choice would be the Nikon Coolpix 5400, but the Canon seems like a great system. Thanks in advance.Steve. Link to comment Share on other sites More sharing options...
phule Posted August 21, 2003 Share Posted August 21, 2003 Why would your other choice not be a G3? I seem to recall dpreview.com mentioning that the G3 exhibits far less in the way of fringing. Link to comment Share on other sites More sharing options...
david_haynes Posted August 21, 2003 Share Posted August 21, 2003 <a href="http://www.caldwellphotographic.com/TutorialsDistortionAndColorFringing.html">Check this out...</a> Link to comment Share on other sites More sharing options...
peter nelson Posted August 21, 2003 Share Posted August 21, 2003 What's <B>causing</B> the purple fringing?<P> Is it lens flare or chromatic aberration or a signal processing problem? Purple is a common color for lens flare because of the magnesium fluoride lens coating on internal elements. If that's the problema a lens hood will fix it. If it's CA you can reduce it by stopping down. If it's a signal processing problem you're out of luck. Link to comment Share on other sites More sharing options...
Spearhead Posted August 21, 2003 Share Posted August 21, 2003 It's explained in the link given above. Music and Portraits Blog: Life in Portugal Link to comment Share on other sites More sharing options...
bobatkins Posted August 21, 2003 Share Posted August 21, 2003 Good grief Peter, please stop posting crap here. This isn't the only thread where you're WAY off base. The color of flare has nothing to do with lens coatings being MgF (which they probably aren't anyway as multicoatings use multiple materials, including cerium and silicon oxides, not just MgF). What passes for flare may well be CCD/CMOS blooming - a leaking of charge from light to dark elements. I've seen it in every digital camera I've looked at. Shoot a fine dark line (tree branch) against a bright background (the sky) and it will look blue or have a blue outline. However it won't be blue on just one side if it is due to blooming. Of course it may also be flare, but flare isn't generally localized and effects the whole image, reducing overall contrast. It doesn't just manifest itself as purple fringes. Chromatic aberration is different. It results in colored edges to objects near the edge of the frame. Usually one side one color (e.g. blue/purple) and the other side a different color (e.g. yellow). It's a result mainly of lens aberration, though there has been some suspicion it could be caused by the CCD under some circumstances with some types of CCD design. Some sensors use microlenses above the pixles and light coming in at an angle, could, in some circumstances, show chromatic effects. I'm not sure this has ever been experimentally verified though. Link to comment Share on other sites More sharing options...
bobatkins Posted August 21, 2003 Share Posted August 21, 2003 Oh and another thing Peter. Transverse chromatic aberration is NOT reduced by stopping down. Link to comment Share on other sites More sharing options...
peter nelson Posted August 21, 2003 Share Posted August 21, 2003 <I>Oh and another thing Peter. Transverse chromatic aberration is NOT reduced by stopping down. </I><P> True, stopping down only works for logitudinal CA, but transverse chromatic aberration bad enough to cause plainly obvious color fringing in a modern lens would be very unusual. Link to comment Share on other sites More sharing options...
peter nelson Posted August 21, 2003 Share Posted August 21, 2003 <I>What passes for flare may well be CCD/CMOS blooming - a leaking of charge from light to dark elements. I've seen it in every digital camera I've looked at. Shoot a fine dark line (tree branch) against a bright background (the sky) and it will look blue or have a blue outline. However it won't be blue on just one side if it is due to blooming</I><P> Why would CCD blooming make it look blue? There's no difference between the blue elements and the green and red ones except the color of the tiny lenses over them. Also most CCD blooming is along a particular axis reflecting the design of the chip, which is why it produces a characteristic "spike" or line. (I don't know what CMOS blooming might look like - supposedly CMOS is bloom-resistant) Link to comment Share on other sites More sharing options...
peter nelson Posted August 21, 2003 Share Posted August 21, 2003 <I>The color of flare has nothing to do with lens coatings being MgF (which they probably aren't anyway as multicoatings use multiple materials, including cerium and silicon oxides, not just MgF).</I><P> Flare is is caused by internal reflections off the glass surfaces and the color of the flare reflects the color of that reflection. The reason why most lens flare is either purple of yellow is precisely because the coatings. If you don't believe this take some photos through some old, uncoated uptics and note the color of the flare. I have flare-y photos taken with my Argus C-3 that are plain white. All the ones I have taken with coated optics are the same set of colors you see with coated optics, namely purple or gold. Try it yourself. Link to comment Share on other sites More sharing options...
peter nelson Posted August 21, 2003 Share Posted August 21, 2003 And another thing - what is THIS supposed to mean?<P> <I>Good grief Peter, please stop posting crap here. This isn't the only thread where you're WAY off base. </I><P> If you think I'm in factual or scientific error in another thread please take it up in that thread, rather than making ad-hominem attacks in this one. Link to comment Share on other sites More sharing options...
bobatkins Posted August 21, 2003 Share Posted August 21, 2003 I have. It's just that a whole lot of your posts lately seem to have factual and scientific errors in them. I dont believe I'm the only one who has commented on this. Link to comment Share on other sites More sharing options...
peter nelson Posted August 21, 2003 Share Posted August 21, 2003 <I>I have. It's just that a whole lot of your posts lately seem to have factual and scientific errors in them.<P> I dont believe I'm the only one who has commented on this.</I><P> Most people here complain because I have a didactic, pedantic style. But if there is any place where someone has questioned a technical or scientific statement I've made and I have FAILED to respond please let me know and I will endeavor to correct it.<P> Furthermore I'd be interested in seeing how many posts you mean by a "whole lot". Link to comment Share on other sites More sharing options...
bobatkins Posted August 21, 2003 Share Posted August 21, 2003 Peter, well, with respect to CCDs you said <p> "<em>higher ISO's in astronomy CCD's are achieved with higher currents, which result in higher noise</em>" <p> Really? <p> I try not to get personal, but as a moderator here I get complaints from time to time about some posters via email. I don't usually act on them, I often don't reply to them, but I do take note of them. I guess your style tend to rub people the wrong way. Enough said I guess. <p> We should probably all try to check our facts before offering opinions. It just seems lately I've had to remove a bunch of posts (not Peter's) which were just plain full of incorrect information presented as fact. Link to comment Share on other sites More sharing options...
dave_t Posted August 21, 2003 Share Posted August 21, 2003 Bob Atkins wrote: <i>What passes for flare may well be CCD/CMOS blooming - a leaking of charge from light to dark elements</i> <p> OK, I'll bite. If it's blooming, why is it purple? What do chips know about color? Is the color (not the blooming) an artifact of the RAW (why is that always capitalized) converter? Do Foveon type chips show color fringing? I agree that it's probably not CA -- it's too uniform across the field in my digicam, and doesn't seem to care about focal length. I haven't done formal testing, though, so I can't rule it out. Link to comment Share on other sites More sharing options...
todd frederick Posted August 21, 2003 Share Posted August 21, 2003 In spite of the "debate" I appreciate the info. I did some photos of trees with strong backlighting with my digital that gave this purple fringing. I did not know what the problem was. I'm beginning to think there are some photo situations that are wonderful in digital, and others that cry for, and just blossom with film. Link to comment Share on other sites More sharing options...
alan_bolton1 Posted August 22, 2003 Share Posted August 22, 2003 Is this what you guys mean? I've just started fiddling with digital, so excuse my ignorance. Link to comment Share on other sites More sharing options...
bobatkins Posted August 22, 2003 Share Posted August 22, 2003 That's chromatic aberration (blue on one side, yellow on the other) This is the purple fringing effect. Whether it's flare or blooming I don't know, but it's very localized. If it's flare it's probably not lens flare. It might be flare induced by the sensor optics. Lens flare just isn't normally this localized.<div></div> Link to comment Share on other sites More sharing options...
aron Posted August 22, 2003 Share Posted August 22, 2003 "That's chromatic aberration (blue on one side, yellow on the other" Bob, I am not trying to kiss ass, but how heck do know all this stuff? Not specific to the above, just in general, how long have you been doing photography? Maybe thats for another forum. You the man Bob. Link to comment Share on other sites More sharing options...
bobatkins Posted August 22, 2003 Share Posted August 22, 2003 Well, I ran an research lab for 20 years at Bell Labs looking at the optical properties of materials (mostly silica). You tend to pick this stuff up when you work with it every day... Link to comment Share on other sites More sharing options...
robert_m_johnson Posted August 23, 2003 Share Posted August 23, 2003 <div></div> Link to comment Share on other sites More sharing options...
steve_maslin1 Posted August 23, 2003 Author Share Posted August 23, 2003 Ok.. I've just read a user review and noted something of interest. "No noise and CA trouble since i shoot at ISO 50 and use RAW mode most of the time." So from this I am guessing that if I use RAW files all the time that I shouldn't have a problem.. Any one have any ideas on this? Thanks for the replys. Link to comment Share on other sites More sharing options...
bobatkins Posted August 23, 2003 Share Posted August 23, 2003 Yes, it's crap. Using RAW files (or low ISO settings) can't do anything at all about chromatic aberration. Now if the RAW -> Jpeg conversion algorithm is not optimized it could be introducing artifacts, but there's no way it can do anything about chromatic aberration due to the lens. Noise at low ISO settings should always be lower of course. Link to comment Share on other sites More sharing options...
wogears Posted August 25, 2003 Share Posted August 25, 2003 "Yes, it's crap. Using RAW files (or low ISO settings) can't do anything at all about chromatic aberration." This is spot-on. Using a HIGHER ISO might lower CA, but only because the program AE would stop the lens down. Stopping-down will lower CA to some extent, as noted above. Multicoated lenses have distinctive "flare colors" because the coatings do not control flare at all wavelengths equally. This is a part of what give different manufacturers' lens lines a distinctive "look". There are several GUIs for PanoTools; I believe they work well, but have not personally tried them. Les Link to comment Share on other sites More sharing options...
jeremy_allen Posted December 11, 2003 Share Posted December 11, 2003 I own a G5 and I have noticed the purple fringing completely goes away around f/4.0 - f/4.5. I was taking some pictures of a new Mustang Mach I with the reflection directly on the front of the car. I bracketed a lot and went through a variety of settings. In review none of the pictures of the Mustang that were above f/4.0 had the purple fringing, and almost like a different camera took the pictures at <f/4.0 the fringing was there and obvious. I am usually able to compensate for this by simply upping the f stops a bit. Good Luck Jeremy Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now