There's an article on color shading: http://www.dxo.com/intl/more-information-about-color-shading
And it mentions color shading depends on light source too (those artificial light sources give spikes in the spectrum).
And it seems pointing the source of color shading mainly to IR.
Seems like pretty smeared at the corner. He even said, "The CV15 has strong vignetting and loss of sharpness in the corners".
How would it compare to A7? And if CV12 better?
kolen wrote:
There's an article on color shading: http://www.dxo.com/intl/more-information-about-color-shading
And it mentions color shading depends on light source too (those artificial light sources give spikes in the spectrum).
And it seems pointing the source of color shading mainly to IR.
Good article. Phone cameras are transitioning from interference IR filters to absorption type IR filters especially because the acute angular sensitivity of interference filters doesn't play nice when they push the lenses up against the sensors. I researched this a bit and found that Schott have released new blue-green glass types especially designed for making extremely thin IR absorption filters to meet this need from markers. It's not just Leica who are push the engineering in interesting directions.
kolen wrote:
Seems like pretty smeared at the corner. He even said, "The CV15 has strong vignetting and loss of sharpness in the corners".
How would it compare to A7? And if CV12 better?
Based on the results I got with these two lenses on the a7, the CV12 will be the less problematic performer. Edge smearing is less and color shift will be more manageable. I haven't tried a lot of CV12 and 15s, but my impression is there might be some copy variation in these lenses and adapter performance will be more critical with a super-ultra wide. I would also suggest trying to find the LTM version of the CV12 because it's optically identical but much, much smaller without the built-in hood of the M version.
ryankarr wrote:
Why do you have to have ordered the camera to make comments on image quality?
I suggest that anyone who would like to post on this subject needs to provide a proof of purchase beforehand. Please scan your preorder receipt and add it at the bottom of your post. Failing to do that will have very serious consequences. And no, owning RF lenses does not entitle to post. Thank you.
rscheffler wrote:
Based on the results I got with these two lenses on the a7, the CV12 will be the less problematic performer. Edge smearing is less and color shift will be more manageable. I haven't tried a lot of CV12 and 15s, but my impression is there might be some copy variation in these lenses and adapter performance will be more critical with a super-ultra wide. I would also suggest trying to find the LTM version of the CV12 because it's optically identical but much, much smaller without the built-in hood of the M version.
Are there differences in coating?
uhoh7 wrote:
For centuries it was obvious the sun revolved around the earth.
Sorry pal, the A7 sucks less with RF wides indeed (it doesn't mean it works well with them).
p.117 #10 · A7/A7r - performance with WA RF lenses
kolen wrote:
There's an article on color shading: http://www.dxo.com/intl/more-information-about-color-shading
And it mentions color shading depends on light source too (those artificial light sources give spikes in the spectrum).
And it seems pointing the source of color shading mainly to IR.
That article is mostly written with respect to small/micro system cameras in surveillance/phone modules. Most cameras for normal use (i.e almost all ILC type cameras you can buy as a private person) use hybrid filters. They usually have a hot-mirror surface tuned to about 700nm on an absorption plate that starts to cut already at 570-580nm - any other solution combined with silicon-based photo-diodes gives a very strange color rendition.
Any tuning giving significant shading due to the hot-mirror alone means that you've long since f*cked up the color rendition - allowing strong near-IR bandwidth content in to increase noise performance will give extremely low metamerism index results. All colors from warm green and out past red will be skewed.
Typically a hot-mirror surface will go from 700nm to about 630nm tuning from 0-50º (pretty extreme) incident angle, and less than 20% of the total red channel sensitivity should be in that region if you want a camera to see color like the human eye.
20% is an increase in red strength by 2log(1.20) = 0.25Ev, which wouldn't give much of a color cast. Noticeable, but not really that disturbing. Most of that would be removed by the increase in absorption plate path length (45º incident on a plate with RI 1.5 gives 28º, meaning a 15% increase in path length > 15% increase in filter attenuation).
I get quite high channel G>R and G>B contamination going from 0-35º incident angles even on a totally naked sensor when using monochromatic light (slightly diffused 532nm laser from a normal presentation pointer device). IMO this means that most of the color shading happens in the sensor, not on the UVIR system - though the UVIR plates definitely makes it worse.
p.117 #12 · A7/A7r - performance with WA RF lenses
Thanks for the interesting explanation. It makes sense. Vivek at getdpi was saying a similar thing as nex-5n and/or 6 is very sensitive to infrared vs A7/A7R are not. That gave me a similar conclusion eg the sensor topping issue due to the infrared sensor...
edwardkaraa wrote:
There was a very interesting comparison on LUF between the M and A7r in a controlled studio setting using the 35 cron on both cameras, and the 35 FE on the A7r. I am not talking about lens performance here because both lenses performed almost identically in this close up shoot out. But what I found very important and essential to understand how these cameras work is that there was a black synthetic fabric gear bag in the frame. It was rendered as purple in the M shot, while it is a pure black in the A7r shot.
Now to put things in perspective, for those not familiar with this issue, the 1.3x crop factor M8 had a very thin UV/IR cut filter to minimize corner smearing, but that introduced what is called IR contamination, causing black synthetic fabrics to become purple, as well as screwing the colors up completely in situations with high IR. The M9 is said to have a thicker filter, and exhibits this problem to a much lesser extent, but still visible in some situations. the M filter is suspected to be slightly thinner to take in account the higher mp and the new microlens design, hence the higher IR contamination.
Now it has to be that Sony decided to put a proper strength/thickness IR filter in front of the sensor, first because color is very important for Sony, second because the lenses are specially designed for the sensor, so a problematic ultra thin filter is not really needed. The result of which is high fidelity color and corner smearing with RF wides, but why should Sony care. So, as Kent likes to say, pick your poison, would you like smearing, or IR contamination, or a bit of both?
p.117 #13 · A7/A7r - performance with WA RF lenses
While all this makes perfect logical sense, it doesn't explains why the Ricoh GXR-M, in spite of having very poor IR sensitivity, it's free from any smearing issues with RF glass. Yes, it's an APS-C sensor, but so it is the NEX-7.
p.117 #14 · A7/A7r - performance with WA RF lenses
Not a WA but worth mentioning, I found that the sensor of the A7R doesn't pair well with the 50 Summilux. It's quite sharp in the center at f/1.4 but overall contrast and micro-contrast quickly and strongly declines so stopping down to f/2.8-f/4 is necessary to get anything one can call "sharp" away from the center.
BTW, I use a Metabones adapter.
p.117 #15 · A7/A7r - performance with WA RF lenses
artur5 wrote:
While all this makes perfect logical sense, it doesn't explains why the Ricoh GXR-M, in spite of having very poor IR sensitivity, it's free from any smearing issues with RF glass. Yes, it's an APS-C sensor, but so it is the NEX-7.
Indeed I have used a GXR-M for a short period before acquiring the M9, and it's true it doesn't smear nor has a particular problem with IR. But as you say it's a crop sensor, and also note that the M9 that is FF has neither of these problems. In fact, the M9 has a sensor cover that is thick enough to deal with IR but not too thick to cause smearing. It's a matter of finding the right balance. The GXR sensor has been tuned to give an exact replica of the M9 colors so I wouldn't be surprised if it uses exactly the same sensor cover specifications.
p.117 #16 · A7/A7r - performance with WA RF lenses
Blackout wrote:
Not a WA but worth mentioning, I found that the sensor of the A7R doesn't pair well with the 50 Summilux. It's quite sharp in the center at f/1.4 but overall contrast and micro-contrast quickly and strongly declines so stopping down to f/2.8-f/4 is necessary to get anything one can call "sharp" away from the center.
BTW, I use a Metabones adapter.
I've been specifically interested in purchasing both A7r and Lux 50 ASPH to use together, so your comments are of particular interest.
Are you using the ASPH?
Are you hitting infinity focus at the hard stop, or is the Metabones letting you focus a bit past infinity?
Can you possibly post any photos that show the problem with wide open focus toward the sides?
p.117 #17 · A7/A7r - performance with WA RF lenses
turnstyle wrote:
I've been specifically interested in purchasing both A7r and Lux 50 ASPH to use together, so your comments are of particular interest.
Are you using the ASPH?
Are you hitting infinity focus at the hard stop, or is the Metabones letting you focus a bit past infinity?
Can you possibly post any photos that show the problem with wide open focus toward the sides?
Thanks!
Sure, let's go.
Yep, it's the ASPH (a brand new sample), and I'm hitting infinity at the hard stop.
Now two full-size samples, converted from RAW with slight exposure tweaks at the most, and noise reduction off.
You can see how sharpness and contrast degrade rapidly over the plane of focus, from the center to the edges. I got much, much better results ie. with the Sigma 35mm f/1.4 wide open on the D800E. I have a picture from the same subject shot with that combo, and it's night and day.
It reminds me of how the Zeiss 50mm f/1.4 Planar rendered at close focusing distances, with low contrast and sharpness because it has no floating element, but the problem here obviously has other roots. And it was acceptable near infinity even wide open.
Steve Huff keeps telling me that it's normal, that it's a matter of DOF only, which is obviously wrong: it's sharp (but not jaw-dropping either) in the center but nowhere else, yet the plane of focus slices the cactus in the first scene and the trees in the second.
I'm on the verge of getting the Zeiss Otus in place of the Summilux. I'm willing to trade size and weight to get the most out of that sensor. Focus peaking is enough of a reason for me to shoot the A7R over a DSLR.
p.117 #18 · A7/A7r - performance with WA RF lenses
Blackout, between the Otus and the summilux, I think the only thing going for the lux is size, if you can live with that, the Otus is superior by a long shot, IMHO.
p.117 #19 · A7/A7r - performance with WA RF lenses
edwardkaraa wrote:
Blackout, between the Otus and the summilux, I think the only thing going for the lux is size, if you can live with that, the Otus is superior by a long shot, IMHO.
I'd probably just split the difference and get the FE 55.
