IkarusJohn Posted August 8, 2015 Share #1 Posted August 8, 2015 Advertisement (gone after registration) I promised wattsy I'd run a bit of a test in another thread. I forgot my tripod, and was a bit underwhelmed with subjects, so I chose the Sea Scouts clubhouse at Devonport - middle distance, handheld, ISO 320, Noctilux, focused using a 1.4x magnifier. I maintained the aperture at between f4 & f5.6 to try to control the depth of field, shutter speed between 1/3,000 and about 1/1,000. What we're looking for here is a shift in the depth of focus - that is the clarity of the image at the sensor resulting from the shift to an all red wavelength. The first is our control shot, taken without any filter. In all shots I've focused on the corner of the building - sorry again it's a bit of a boring shot. I've done pretty much no post processing, other than cropping to give the same image. Happy to provide the DNGs to anyone who wants them. Welcome, dear visitor! As registered member you'd see an image here… Simply register for free here – We are always happy to welcome new members! Link to post Share on other sites Simply register for free here – We are always happy to welcome new members! ' data-webShareUrl='https://www.l-camera-forum.com/topic/248723-red-filter-on-monochrom/?do=findComment&comment=2868351'>More sharing options...
Advertisement Posted August 8, 2015 Posted August 8, 2015 Hi IkarusJohn, Take a look here Red Filter on Monochrom. I'm sure you'll find what you were looking for!
IkarusJohn Posted August 8, 2015 Author Share #2 Posted August 8, 2015 Next, same shot, but with a Heliopan Yellow 15 filter Welcome, dear visitor! As registered member you'd see an image here… Simply register for free here – We are always happy to welcome new members! Link to post Share on other sites Simply register for free here – We are always happy to welcome new members! ' data-webShareUrl='https://www.l-camera-forum.com/topic/248723-red-filter-on-monochrom/?do=findComment&comment=2868352'>More sharing options...
IkarusJohn Posted August 8, 2015 Author Share #3 Posted August 8, 2015 Finally with a Heliopan Red 25 Welcome, dear visitor! As registered member you'd see an image here… Simply register for free here – We are always happy to welcome new members! Link to post Share on other sites Simply register for free here – We are always happy to welcome new members! ' data-webShareUrl='https://www.l-camera-forum.com/topic/248723-red-filter-on-monochrom/?do=findComment&comment=2868353'>More sharing options...
IkarusJohn Posted August 8, 2015 Author Share #4 Posted August 8, 2015 Here's a crop from the centre of the last one. Welcome, dear visitor! As registered member you'd see an image here… Simply register for free here – We are always happy to welcome new members! Link to post Share on other sites Simply register for free here – We are always happy to welcome new members! ' data-webShareUrl='https://www.l-camera-forum.com/topic/248723-red-filter-on-monochrom/?do=findComment&comment=2868354'>More sharing options...
250swb Posted August 8, 2015 Share #5 Posted August 8, 2015 So what is your conclusion? I can't see too much wrong with the crop shot, but there's nothing to compare it with. As has been said the red wavelength is problematic in all aspects of photography, it's just that B&W shows it up more often if it is going to be a problem. Steve Link to post Share on other sites More sharing options...
IkarusJohn Posted August 8, 2015 Author Share #6 Posted August 8, 2015 I can't see a problem. Link to post Share on other sites More sharing options...
fiftyonepointsix Posted August 9, 2015 Share #7 Posted August 9, 2015 Advertisement (gone after registration) http://www.l-camera-forum.com/topic/247310-color-filters-chromatic-aberration-and-focus-shift/ I believe that any focus shift is due to chromatic aberration of the lens. I did a test with a Pentax 85/4.5 Ultra-achromatic lens on the M Monochrom, same filters used on a Pentax 50/1.4 on the M Monochrom. Shift in the point of focus was evident on the 50/1.4 Achromat (corrected for two zero-crossings) but not on the 85/4.5 (corrected for four zero-crossings). The 85/4.5 is a fluorite and quartz lens, for use from UV through to Infrared. Link to post Share on other sites More sharing options...
IkarusJohn Posted August 10, 2015 Author Share #8 Posted August 10, 2015 Both the Noctilux 0.95 and the Summilux 50/1.4 ASPH are APO lenses, apparently. I do have comparative images taken with the Summincron 28/2 ASPH, which is not an APO lens - I will fish those out tonight. Link to post Share on other sites More sharing options...
IkarusJohn Posted August 10, 2015 Author Share #9 Posted August 10, 2015 Okay, so here is the Summicron 28/2 ASPH, no filter Welcome, dear visitor! As registered member you'd see an image here… Simply register for free here – We are always happy to welcome new members! Link to post Share on other sites Simply register for free here – We are always happy to welcome new members! ' data-webShareUrl='https://www.l-camera-forum.com/topic/248723-red-filter-on-monochrom/?do=findComment&comment=2869254'>More sharing options...
IkarusJohn Posted August 10, 2015 Author Share #10 Posted August 10, 2015 And here it is with a B+W red 46 091 Welcome, dear visitor! As registered member you'd see an image here… Simply register for free here – We are always happy to welcome new members! Link to post Share on other sites Simply register for free here – We are always happy to welcome new members! ' data-webShareUrl='https://www.l-camera-forum.com/topic/248723-red-filter-on-monochrom/?do=findComment&comment=2869255'>More sharing options...
IkarusJohn Posted August 10, 2015 Author Share #11 Posted August 10, 2015 I can't see any focus shift - in both images, I was focusing on the shed roof on the waterfront to the left of the wharf. Link to post Share on other sites More sharing options...
wattsy Posted August 10, 2015 Share #12 Posted August 10, 2015 Fair enough, John. I'll do a more scientific test (at least use a tripod) with my red filter and 35 Summilux at some point in the near future and see if I can replicate the problem I previously observed. Link to post Share on other sites More sharing options...
250swb Posted August 10, 2015 Share #13 Posted August 10, 2015 The red focus shift should be apparent with the lens wide open, otherwise depending on the lens DOF will often cover it, so if it is going to be apparent it's wide open lenses or tele lenses that have narrow DOF. But my guess would be it's a rarefied set of events that makes people put a strong red filter on the lens and not want to stop it down for more DOF at the same time, such as in typical landscape photography. Steve Link to post Share on other sites More sharing options...
IkarusJohn Posted August 10, 2015 Author Share #14 Posted August 10, 2015 I'm not saying the issue doesn't exist, and I would be very interested to know when it becomes an issue. I would have to say that if what Steve says is true, it would most likely be an issue wide open with a subject at middle distance. Not sure I'd use a red filter for an image like that ... i will ill give it a go, and I will get my tripod out. Any other ideas welcome. Link to post Share on other sites More sharing options...
John McMaster Posted August 10, 2015 Share #15 Posted August 10, 2015 I found focus shift at <5m and wide open on a variety of lenses 21mm and up john Link to post Share on other sites More sharing options...
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