p.21 #1 · A thinner sensor stack may be possible after all!
Gary Clennan wrote:
I could see it *potentially* being an issue with wedding photographers but for most all others it would not matter at all.(
Yeah, Wedding photographers, Studio photographers (who probably don't shoot Leica for other reasons) and so forth. Not that I would use a Leica M for it anyway, but the IR contamination would be a worry for me shooting color critical art work. I could also see it as an issue for those who shoot interiors (where certain fabrics might show the IR contamination). Street shooters might not care as much - or might not notice unless they go looking for it. In any case, this alone would explain why a Canon, Nikon, Olympus, Ricoh (for Pentax DSLR's) or even Sony might avoid the issue all together for their customers if IR pollution can't be avoided going with a very thin cover glass.
p.21 #2 · A thinner sensor stack may be possible after all!
Matt Grum wrote:
They've chosen to design lenses from scratch and to obtain the performance figures they want they will probably need to go with larger retrofocal designs anyway, so there is no real advantage to Sony in having a thinner stack.
With respect, could not disagree more.
There are two critical factors which certainly have a direct effect on sales short and long term for the series.
1) the thicker stack means tiny lenses are more problematic. Completely compromises the form factor advantage.
2) the thicker stack frustrates a influential market segment who know exactly what the best small lenses are, or simply love to play with legacy glass, or who are invested in other wides, like a 1740, which is alot better on the 5D than the A7, as Fred has shown.
also, I'd thought with removal of AA with this mod, I'd see moire, a la M9. Not yet. I see it in the EVF all the time, but not in still. Guess I should shoot some movies
At least today there is a true wide option for the stock machines, but it's slow and big: the 1635.
A nice thin stack as seen on M9 or canon 1d-c would let Sony have it's cake and eat it too. Now they are stuck.
But they don't care, because these are throw away items, to be replaced by another different, likely equally half-baked system, with totally different sensors and issues within a few years.
I guess once you've made the walkman the damage to corporate humility is irreparable.
But it's OK. Despite Sony's many blind spots they have put us ahead, and the sales volume is enough to support a mod like this, which has totally resurrected the A7 for me (not to mention the many wonderful shots made with the system as-is by better shooters)
p.21 #4 · A thinner sensor stack may be possible after all!
Tariq, if it weren't that you're a long term and well appreciated contributor of this forum, I'd suspect that you have a sort of hidden agenda to insist in the IR issue with the Leica M240.
Edward said that of all the pictures he has taken with the camera ( probably thousands) only once he saw a slight reddish tone in a sintetic black. I read quite often the 'Leica user forum' and frankly I don't recall a single angry complaint of anybody concerning that matter.
If you believe that this is a serious problem. you're entitled to your opinion of course. It seems though that most people has another point of view.
Not only Leica has released cameras dedicated tor M glass -i.e. with very thin IR filters and no AA filter. Ricoh did it with the A12 M mount module for the GXR.
I happen to own still one of these 'venerable' ladies and I haven't seen any IR contamination. In fact, the A12 module is absolutely useless for IR photography. If I use a IR720 cut filter on any lens with the A12 module, I need to increase ten or eleven stops the regular exposure for normal light in order to get something barely visible.
Below there's a quick shot with the GXR-M from a few minutes ago, Light is an halogen lamp around 3000K. That battered Cullman bag was awfully purple with the M8 without IR cut filter.
I tuned the WB until the grayscale card was neutral. Do you see any red/purple tone on the black bag ?. I don't.
p.21 #5 · A thinner sensor stack may be possible after all!
It would be interesting to know how thick the glass is on the GXR's A12 module's sensor. (BTW, I also still have mine) I suspect because it's 'only' APS-C, removing the AA was a big step towards better edge performance and that it wasn't as critical to reduce glass thickness. At least not to the degree required for a FF sensor.
With the M240, yeah, I think it depends a lot on what you photograph *and* how critical you are. I see it a fair amount, but maybe I'm just tuned to it, or critical about it. If it's an image I post somewhere, I fix it. Viewers could be of the impression there isn't a problem, unless I mention it each time. That said, it's not like it's something I'm fixing all the time. Hardly.
It looks fine because I fixed it, but it's one of a series of photos where the fleece rendered brown rather than black. Brown because the purple IR contamination plus warm evening sunlight. Me being a bit anal about this, I did a quick desaturation of the fleece, so you'll have to trust me. Not a big deal as it was maybe 10-15 images. But as Tariq indicated, where I've seen it most is at weddings, or generally people/events I photograph. It's a problem of certain synthetic materials, and the worst was the wedding last summer where the guys were all in gray suits and the lapels had a different kind of gray material that turned pink. PITA. Zero indication of this with the Canon, but it was the case in every Leica image.
Maybe it's a good way to screen potential wedding clients - synthetic suits? No thanks. Wool suits? OK!
I'll have to dig some up, but currently I don't have any of those online.
That said, it's not anywhere near to the point where it's a deal breaker for me.
BTW, this is not a problem unique to Leica. IIRC, Nikon has had problems with this too, such as with the D2H.. which the newspaper I worked at used for some time. It was a headache when PPing photos from the local football team's games - their home uniform is mostly black with yellow, and the black would often go brownish. Maybe it's why I'm apparently sensitive to this effect?
Charlie: even a seemingly modest jump to 24MP will make a difference to how often you see moire. Or so I think because I see it a lot less with the M240 vs. the M9. I couldn't imagine photographing people in suits, etc. with the Canon 1D again. It was a real pain in 2002-4...
p.21 #6 · A thinner sensor stack may be possible after all!
artur5 wrote:
Tariq, if it weren't that you're a long term and well appreciated contributor of this forum, I'd suspect that you have a sort of hidden agenda to insist in the IR issue with the Leica M240.
Edward said that of all the pictures he has taken with the camera ( probably thousands) only once he saw a slight reddish tone in a sintetic black. I read quite often the 'Leica user forum' and frankly I don't recall a single angry complaint of anybody concerning that matter.
If you believe that this is a serious problem. you're entitled to your opinion of course. It seems though that most people has another point of view.
Not only Leica has released cameras dedicated tor M glass -i.e. with very thin IR filters and no AA filter. Ricoh did it with the A12 M mount module for the GXR.
I happen to own still one of these 'venerable' ladies and I haven't seen any IR contamination. In fact, the A12 module is absolutely useless for IR photography. If I use a IR720 cut filter on any lens with the A12 module, I need to increase ten or eleven stops the regular exposure for normal light in order to get something barely visible.
Below there's a quick shot with the GXR-M from a few minutes ago, Light is an halogen lamp around 3000K. That battered Cullman bag was awfully purple with the M8 without IR cut filter.
I tuned the WB until the grayscale card was neutral. Do you see any red/purple tone on the black bag ?. I don't.
It's just a matter of reiterating the possible drawbacks of thin cover glass, which goes to the discussion of why other manufacturers might have chosen to go with thicker glass. The M does suffer some IR contamination. For the core user group, it might not matter given the upside. That said, it exists and it somewhat ruffles my feathers when facts are glossed over and whitewashed - regardless of the brand or whether I own the equipment or not. I think folks should have the facts and then decide if anything is a possible issue for their use.
There are Leica M users who are using IR cut filters on front of the lens anytime they use the M240 for critical color work and have unquestionably proven that IR contamination can be an issue with the M240. I really don't think this is in dispute. In fact, some Leica users are saying that the M240, while not nearly as bad as the M8, does pass more IR than the M9.
p.21 #7 · A thinner sensor stack may be possible after all!
Tariq Gibran wrote:
It's just a matter of reiterating the possible drawbacks of thin cover glass, which goes to the discussion of why other manufacturers might have chosen to go with thicker glass. The M does suffer some IR contamination. For the core user group, it might not matter given the upside. That said, it exists and it somewhat ruffles my feathers when facts are glossed over and whitewashed - regardless of the brand or whether I own the equipment or not. I think folks should have the facts and then decide if anything is a possible issue for their use.
There are Leica M users who are using IR cut filters on front of the lens anytime they use the M240 for critical color work and have unquestionably proven that IR contamination can be an issue with the M240. I really don't think this is in dispute. In fact, some Leica users are saying that the M240, while not nearly as bad as the M8, does pass more IR than the M9.
Agreed. It's important to discuss both the positives and negatives of removing or changing things like AA filters and cover glass. It's not as if Sony is dying to use potentially more expensive parts. They likely just wanted to use a cover glass similar to their DSLRs, since they promote cross compatibility of their systems, and their DSLRs didn't have thin filters, because they didn't need to use them for SLR lens designs, so fragility and IR contamination weren't worth the trade off. Granted, as theSuede has mentioned, Sony could have used some higher quality cover glass in the past on their DSLRs, but I don't think the thickness was much of an issue on cameras like the A900.
p.21 #8 · A thinner sensor stack may be possible after all!
rschefflerwrote: Maybe it's a good way to screen potential wedding clients - synthetic suits? No thanks. Wool suits? OK!
Sure enough; there are visible traces of IR contamination on poly* materials, but examples below may be the worst scenerio. If so, I can easily put up with it as this slight, occasional discouration issue pales in comparison to benefits Kolari mod offers.
p.21 #9 · A thinner sensor stack may be possible after all!
JaKo wrote:
Sure enough; there are visible traces of IR contamination on poly* materials, but examples below may be the worst scenerio. If so, I can easily put up with it as this slight, occasional discouration issue pales in comparison to benefits Kolari mod offers.
I'm curious as to how the B+W UV filter acts to block IR? Isn't it just a UV filter? I can see how it would get rid of UV contamination from say non-corrected strobes - or if there is some UV blocking issues with the camera/ cover glass - but IR? Seems like you would need the combined UV/IR cut filter for that (or is that what you used?).
p.21 #10 · A thinner sensor stack may be possible after all!
Tariq Gibran wrote: I'm curious as to how the B+W UV filter acts to block IR? Isn't it just a UV filter? I can see how it would get rid of UV contamination from say non-corrected strobes - or if there is some UV blocking issues with the camera/ cover glass - but IR? Seems like you would need the combined UV/IR cut filter for that (or is that what you used?).
It's one of these B+W MRC UV-IR Cut filters in 46mm I got with my Lux 50
p.21 #12 · A thinner sensor stack may be possible after all!
I suspect that there may be some minor IR contamination with the M240, but I think this can be a subtle issue with other cameras as well (probably largely dependent on the thickness of the cover-glass used). I suspect that we may be a bit over-sensitive to IR contamination on Leicas since the M8 had such a significant issue, and we have this faulty sense that a camera that costs so much shouldn't have any issues like this. For me the simple solution is to use UV/IR cut filters for focal lengths 35mm and longer.... for wider lenses the filters cause more issues than the minor IR contamination they are addressing.
p.21 #13 · A thinner sensor stack may be possible after all!
My A7rM just arrived back this late this morning from Kolari Vision. Testing the ArM with the 50 Lux Asph is a wonderful combination. I love the A7II but having the very small footprint of the A7r with 50 Lux Asph is a very powerful package.
First test shot this afternoon.
A7rM and 50 Lux Asph f/1.4
p.21 #14 · A thinner sensor stack may be possible after all!
Actually, there is a lot more to it than the thickness of the filter, although for in-situ filters (vs interference filters like the B+W 486) thicker absorbs more (of everything, including IR).
The selection of the glass type can easily have orders of magnitude more effect than reducing the thickness by a factor or two or three.
The challenge is finding a filter that both provides the correct (or close enough) visual band shaping to maintain the white balance tuning of the sensor+firmware system while still providing good enough IR and UV blockage. I believe the M8 issues were less about the thickness, although it contributed to the problem no doubt, and more the filter glass selection.
If anyone would like to study this more, the Schott glass transmission curves are all in their technical data section. You will see that the IR blockage of the various Blue-Green (BG prefix) glasses used by virtually all manufacturers vary by several orders of magnitude and the sharpness of their cut-offs similarly vary widely. Reducing the thickness by half effects it only by a factor of 2.
As to why not use interference filters, which are surface coatings and unaffected by glass thickness, they have (as mentioned above) issues with large ray angles, so are not a good solution for this application.
p.21 #15 · A thinner sensor stack may be possible after all!
charles.K wrote:
My ArM just arrived back this late this morning from Kolari Vision. Testing the ArM with the 50 Lux Asph is a wonderful combination. I love the A7II but having the very small footprint of the A7r with 50 Lux Asph is a very powerful package.
First test shot this afternoon.
A7rM and 50 Lux Asph f/1.4
Hi charles,
Do you have SEM21/3.4 ASPH? Any test shot from it would be great!
p.21 #16 · A thinner sensor stack may be possible after all!
mdemeyer wrote:
The challenge is finding a filter that both provides the correct (or close enough) visual band shaping to maintain the white balance tuning of the sensor+firmware system while still providing good enough IR and UV blockage. I believe the M8 issues were less about the thickness, although it contributed to the problem no doubt, and more the filter glass selection.
I've been under the impression that the M8 and M9's cover glass were similar, outside of the M8's being .5mm, and the M9's being .8mm.
p.21 #17 · A thinner sensor stack may be possible after all!
phuang3 wrote:
Hi charles,
Do you have SEM21/3.4 ASPH? Any test shot from it would be great!
No, I just sold my 21 SEM a few weeks before I knew about the modification. The results as presented by Lloyd Chambers with the 21 SEM and A7rM are very definitive. Had I known, I would have kept both the 21 SEM and the 28 Cron Asph
p.21 #18 · A thinner sensor stack may be possible after all!
charles.K wrote:
No, I just sold my 21 SEM a few weeks before I knew about the modification. The results as presented by Lloyd Chambers with the 21 SEM and A7rM are very definitive. Had I known, I would have kept both the 21 SEM and the 28 Cron Asph
Too bad... I have the 21 SEM and never use it. I bought it even before A7/A7r was announced. At that time, I was waiting for the rumoured "NEX 9", but SONY released the A7/A7R which is a disappointment to me. Now, your A7rM may be the savior.
p.21 #19 · A thinner sensor stack may be possible after all!
douglasf13 wrote:
I've been under the impression that the M8 and M9's cover glass were similar, outside of the M8's being .5mm, and the M9's being .8mm.
The M9 was Schott S8612. I don't know exactly what glass type the filter M8 was but, as it did not exhibit sensitivity to humidity as does the M9, I believe it was a different glass in addition to being thinner.
. In any case, this alone would explain why a Canon, Nikon, Olympus, Ricoh (for Pentax DSLR's) or even Sony might avoid the issue all together for their customers if IR pollution can't be avoided going with a very thin cover glass. 
