uhoh7 Offline Upload & Sell: Off
|
realVivek wrote:
Charlie, Have you tried shooting in IR with the UT variant? Looks like (from wild variations in WB) it would work for near IR.
Hi Vivek,
Sorry I need to catch up. How would you suggest I try it? I'm all ears
mdemeyer wrote:
I find the AWB in the A7 to be somehow sensitive to aperture, for reasons I can not come up with a theory for. This is true unmodified and with the v1,2, and 3 thin filter mods. Any ideas why?
Also, after a better technical brief from Ilija at Kolari I will have a camera switched to the UT mod and share some comparisons.
Michael
Michael, I'm very excited you will try the UT!
What I think may help in this idea, is to get beyond the obvious and consider what exactly Sony has sandwiched in those thick stacks. Clues again, come from the Astro people, who talk about the various layers in cameras they are taking apart, in some cases down past the CFA. I find references to color filters, independent of the IR cut.
The M9 has a pretty radical WB shift with 28 cron when you go WO. This may be related, as the Leicas are the simplest in terms of the "mix" of filters over the sensor.
In addition, I have also recently discovered the glued coverglass in Canikon is not always clear.
But I do feel the V1 and V2 WB is more "stable" than the UT. However that is not stay in the end a better result may be had from the UT, just that AWB is more varied. I see much more saturation with the UT. It tones down easy enough.
sebboh wrote:
i tried to test charlie's theory on slr wides improving with the thin filter today on the only suitable lens i had lying around. not sure that i see an obvious conclusion from these... caveat is the lens has a floating element and i have to use different adapters for each camera.
Hi Derek, I can't tell anything there, but the range is not the same. At some point you be around a stock A7 I'm sure and we can get a better look with any SLR lens you have.
I'll be shocked if there is no difference.
"What about lenses designed for little or no sensor stack? Actually, it’s already been shown they don’t do well on camera with significant sensor stacks. Panavision has made premium lenses for their film cameras for many years. Recently they’ve released their Primo V series of lenses, which are their Primo lenses modified, according to their website to ” eliminate coma, astigmatism, and other aberrations caused by the extra layers of glass in digital cameras.” U. S. Patent application 14/024,578 describes adding additional optics to the existing lenses to correct for the glass in the imaging pathway, that is between the rear of the lens and the camera sensor."
Roger at Lens Rentals.
My seat of the pants feelings certainly may be wrong, but often they are right. What they tell me:
FD 35/2 thorium, and nFD 24/2 are different on the v2 compared to stock cameras.
One thing we already know: the stock cameras vary widely on how they work with particular film lenses, even between each other. The best example is Charles K and the 75 Lux. He liked it fine on A7s and other early A7 models. Shooting it on the R2, he sold the lens. Charles has a scientific background and a very keen eye.
We are pulling all sorts of things out from in front of the sensor besides the plain properties of optical glass, which are certainly significant themselves. Now, maybe some of those things are better left in. I can see a day when other filters are added to an IR cut in a mod which starts with new glued coverglass. Anyway, my point is: better or worse in various respects, but being the "same" is not likely.
One of my heroes at LUF is Adan, and he has a hilarious series of posts about what is the base ISO of the M10. At first he convinces most readers it's 200, and he's quite emphatic. Then he changes his mind altogether, and proceeds to show it's 100 after all, as the onlookers gape, aghast. That thread is active now. Adan is more agile technically than me, but I hope I have the same attitude.
artur5 wrote:
Do we know for a fact that Canon DSLRs have a thinner sensor stack than Sony A7 series ?
In the context of FF, A7 vs Canikon, yes we know for a fact the Sony is much thicker, actually and "optically". In our context, I believe Roger's idea of "optical thickness" is simply RI times actual thickness. Since the RI in all the glasses varies between 1.4ish to 1.6ish, and the actual thickness varies between 1.1 (D810) and 1.9 (A7), you can easily see which is the primary factor. The bigger Canikon FFs are thinner yet. You must add at least .5mm to that for the base coverglass in those cameras and then compare to Leica, which has NO filter stack, only coverglass which is the IR cut. So the Sony is literally 1.9mm thicker, give or take .3mm. No variable of RI viable for Sony will make the difference anything less than huge.
The whole term of "optical thickness" should be thrown out of this thread. First, it has a bunch of meanings, so it is extremely confusing to research. Second, those "optical thickness" numbers we have now from Lens Rentals are totally suspect. Roger did not make them. We don't know how they were calculated, and if other variables were introduced. Yes, there are thin films which increase optical depth in other contexts dramatically, But not the other way around. So the Sony soup in that thick stack has the potential to make things extra thick, but not extra thin. On the other hand, the Leica is dead simple. My M9 has a sheet of .8mm S8612 over the sensor. Optical properties are well documented and you can look them up. Same for Sam Lee and NK.
The physical thickness as a comparison in this context is conservative. It's easy to verify. It's what the techs are talking about and the DIY astro people. Optical thickness is multi-context, and will only amplify what the physical measurements are giving us, considering the materials we are working with. For us, discussing optical thickness will not help in making a better mod, but just confuse things to no end.
That said, what would be very nice to know: more about what's in the soup of the stock cameras' cover glass and filter stacks.. That might inform a super-mod someday
People who are members at the paid Nikon and Canon technical forums could really help us if they learn more about the glass Canikon is using at various levels above the sensor in FF cameras. I know there are people in those forums who know alot about it. I've seen some of them scoff at Leica and note more sophisticated and expensive filters over the sensor developed by Canikon, especially for the big DSLRs.
Edited on Mar 24, 2017 at 07:20 PM · View previous versions
|