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| Losing the low pass filter - Page 1 | |
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| Posted: Mon Feb 25th, 2013 12:04 |
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1st Post |
Eric
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The D800E has lost it...the D7100 has lost it. So is it replaced with a plain glass filter? If not...How do they protect the sensor? How do they CLEAN the sensor? Has this any impact on lens hotspotting? :baffled:
____________________ Eric |
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| Posted: Mon Feb 25th, 2013 12:34 |
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2nd Post |
Robert
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On all DSLR cameras I have examined and investigated the sensor already has a thin glass outer shield which seals the actual sensors from any possibility of contact. I don't know if the LPF has been replaced by a replaceable piece of protective glass. I suspect it has because it will be needed to maintain optical consistency for the digitally corrected optics of modern 'digital corrected' lenses. There is a little confusion about exactly what the LPF is. On all the cameras I am aware of the LPF performs several functions. It is very slightly etched to very slightly blur the image which falls on the sensor, this cures the moir© effect but also reduces sharpness slightly, except on the D200 where it reduces sharpness a lot. Well that''s my excuse for soft images!!! The LPF also has strong UV and IR Filtration because unlike film, sensors are very sensitive to IR and UV. If it weren't there the image would include the data of the IR and UV spectrums, which apart from confusing the image, would cause blurring because of the focus shift at those wavelengths. The LPF also has the effect of interfering with the light path and bending the light path at the corners and edges of the image sensor, the further from the axis, the greater the bend. It is the corrections for this effect which justify the 'corrected for digital' label. I doubt it will have any great effect on the lens hotspot issue, because I believe there will always be a glass screen of some sort over the sensor. But who knows until you try it?
____________________ Robert. |
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| Posted: Mon Feb 25th, 2013 13:00 |
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3rd Post |
jk
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As Robert says the LPF does a number of things but I guess that the IR and UV filtering is now being performed by another filter in the stack. All they have done is remove the anti-more effect by removing the interference filter component that reduced the image sharpness. There is also the Bayer filter that sits directly above the sensor. See here for the current design. http://dpbestflow.org/camera/sensor This diagram shows it very well. Attachment: camera-microlenses.jpg (Downloaded 31 times)
____________________ Still learning after all these years! https://nikondslr.uk/gallery_view.php?user=2&folderid=none |
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| Posted: Mon Feb 25th, 2013 14:10 |
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4th Post |
Eric
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Robert wrote:On all DSLR cameras I have examined and investigated the sensor already has a thin glass outer shield which seals the actual sensors from any possibility of contact. Hot spotting is a function of the proximity and geometry of the glass surfaces in front of the sensor. The prospect of removing a surface conceivably might have alleviated the issue with some lenses. Mere conjecture I accpet, and in light of JKs drawing, I suspect a vain hope I now concede. 
____________________ Eric |
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| Posted: Mon Feb 25th, 2013 14:31 |
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5th Post |
jk
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Yes removal of the LPF shouldnt improve hot spotting AFAIK !
____________________ Still learning after all these years! https://nikondslr.uk/gallery_view.php?user=2&folderid=none |
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| Posted: Mon Feb 25th, 2013 15:43 |
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6th Post |
Eric
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jk wrote:Yes removal of the LPF shouldnt improve hot spotting AFAIK ! We draw some, we lose some. 
____________________ Eric |
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| Posted: Mon Feb 25th, 2013 16:39 |
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7th Post |
blackfox
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hmmm roberts statement re: digital corrected lenses gives me food for thought ,i wonder if it makes a difference to performance of older lenses ,i.e a 35mm film slr never had a filter in front of the film did it ,the shutter opened and the transmitted light fell on the film ,job done . this is throwing so many variables into the equations ,just had a hour long conflab with my lad who has recently moved back from canon to nikon ,more by chance than choice as he got a 500mm vr f4 at a good price ,and sold all his canon gear to fund it ,but my gut feeling is he still hankers after canon ,whereas i don't i,m fully committed at this point in time. i feel he his upset because they haven't brought out a d400  i digress it will be interesting to see the results and conclusions from the d7100 when it actually hits the shops and users ,either nikon have done something stupid or they have played a blinder ,time will tell 
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| Posted: Mon Feb 25th, 2013 16:53 |
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8th Post |
Robert
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It would be interesting to try my D1X which has the LPF removed in a comparison with my D1 which has a standard IR pass filter (can't recall the wavelength right now) with a range of lenses known to hotspot, like the 50mm f1.4 and the Sigma 10-20 and possibly the 20mm f2.8? I am in recovery mode now the boys have gone back to their mothers after half term, so it would be a nice relaxing way of passing a couple of hours... Good weather forecast for tomorrow... Will charge up the Li-Ion batteries! Edit: No need, they are both fully charged since last year when I went to Bodnant, was that last April Jeff? I won't charge them just to see how they perform having stood best part of a year.
____________________ Robert. |
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| Posted: Mon Feb 25th, 2013 17:21 |
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9th Post |
Robert
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blackfox wrote:hmmm roberts statement re: digital corrected lenses gives me food for thought ,i wonder if it makes a difference to performance of older lenses ,i.e a 35mm film slr never had a filter in front of the film did it ,the shutter opened and the transmitted light fell on the film ,job done . The effect is very easy to demonstrate, If you wind the window of your car down a bit, and put a pencil or a matchstick, anything slim, on the other side of the glass and visible above the glass, view it at 90º to the glass then move your head gradually sideways, the object will appear to split, the light goes through the glass at 90º no matter what angle you view it. The thicker the glass the more pronounced the effect. This is how/why lenses work. The LPF is very thin but we are talking very fine optics here, even the 0.6 mm LPF has an effect which is also more pronounced with lenses which have a deep intrusion into the mirror chamber. Some lenses particularly the longer lenses even have recessed rear elements which effect less distortion. It's nowhere near as simplistic as I describe but it does have an effect and it also affects the edge distortion and edge drop off of light, giving a vignetting effect because of the stretching of the light waves at the edge of the frame. This is also the reason why lenses with a built in filter holder must always have a filter fitted, even if it's clear glass because it's part of the optics of the lens. The old 35mm film lenses will still work and produce great images but for the most part without correction they suffer from slight distortion and apparent vignetting to a greater extent than their modern digitally corrected brethren.
____________________ Robert. |
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| Posted: Mon Feb 25th, 2013 19:49 |
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10th Post |
richw
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I think sometimes we get too caught up in some of this, for most of us it will make no difference to the overall impact and quality of our images.
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