I appreciate Bglick's sharing his results. The fact that meters vary is good info for photographers to have. Thanks!
I appreciate Bglick's sharing his results. The fact that meters vary is good info for photographers to have. Thanks!
“You often feel tired, not because you've done too much, but because you've done too little of what sparks a light in you.”
― Alexander Den Heijer, Nothing You Don't Already Know
>You should always test your exposure meter in connection with your actual experience using the equipment you have. There are so many variables---exposure meter, fil, lens settings, etc.---which can be off that it doesn't make sense to look at each separately. It is how they work together that matters.
Leonard, I can only assume you did not read through this thread before posting. While I do agree testing a meter with your film of choice is a good idea, its impossible to draw sensible conclusions of your tests if you are being fed inaccurate data from your meter. That was the purpose of this post. The message I brought forth has nothing to do with the other issues regarding exposure. It's not an "ALL or nothing" issue, instead, its trying to find the weak link in the chain.... and in this case, that weak link can vary based on the color temp of the light you are metering, or the color temp of the subject if you are spot metering... Considering how large the variances are, (further enforced by the book Brian linked to)..... IMO, if tight exposure is very important to a photog, than these issues are very relevant.
Brian, excellent find! here is some comments from the link you provided....
On Page 91
Most modern meteres use silicon cells which have a high sensiitivy to infra-red and a low sensitivity to blue, violet and ultra violet. This is, of course, the exact opposite of the sensitivity of film. SOME METERS CAN BE GRIEVOUSLY MISLED BY WARM LIGHT (LOW COLOR TEMP) OR BY RED SUBJECTS.
Another interesting point...
Matching a meters sensitivity to a given film - is allegedly done with the Zone VI modified Pentax meters to work with Tri-X.
Its also interesting that Pentax spot meters in their users manual give compensation values up to 1.33 stops based on the color you are spot reading.... further demonstrating how "off" silicon sensors are to color...
If anyone has the Pentax users manual that lists such, it would be nice if they post this info, it is very relevant to this thread. This is the first time I have seen a meter maker define how inaccurate meter readings at different wavelengths of light. Kudos to Pentax on this!!
What I also find interesting is.... the author does not test the meters under different lighting conditions and show his findings.... I would consider this mandatory as an author for a book on exposure meters.... he is clearly dancing around the finding I have presented, but did not go the extra mile and run some real world tests. Like most data in this field, what's available is often "half baked".
So far, I think Nikon is the only manufacturer has addressed this issue head-on. Their approach is brilliant.... isolate the colors in the scene, determine the intensity of each color, and provide exposure data based on how the film will react to these readings. This probably explains the amazing success Nikon shooters have with chrome films with the F5/6 (or possibly previous models).
Question on the Nikon F5/6.... does the film make different exposure decisions based on the type of film you have in the camera? Does the camera know if you have chrome or neg film in the camera? Color or B&W? I know the bar codes on 35mm canisters provide a lot of data, but not sure how much is read by the camera, other then the obvious ISO.
Many of us know Roger Hicks and even he would agree that he is more of a generalist than detail oriented or "scientific". He tends to rely on experience, of which he has lots, and his inate sense of summarizing these experiential findings.Originally Posted by bglick
It really would be nice to have a fully-baked treatise that is presented at a "normal photographer's" level of understanding (whatever that is since it seems to vary quite a bit) -- something that merges the science with real usefull application guidance. I hope that is where this thread ends up; it's not an easy thing to do I would imagine!
> something that merges the science with real usefull application guidance. I hope that is where this thread ends up; it's not an easy thing to do I would imagine!
Yes, this is always the goal..... I would suggest for now, the posting of that Pentax spot metering manual where it states the reading compensation for each color you spot meter is the best, and most simplified approach if one uses a spot meter. However, even this approach leaves out the actual color temp of the light striking the colored subject, but I am certain it is still better than trusting the spot readings with no adjustment factor. What makes the Nikon approach so brilliant is.... its sensor reads the color temp of light that is coming from the subject, which is a mix of the color temp of light striking the subject and the color of the subject itself. The Pentax compensation method assumes a fixed color temp of light striking the subject. This is why, it appears Nikon has created the ultimate color meter for color chrome films.....and the rave reviews through the years support this. Of course, I never even considered having this transpose to LF till others suggested this earlier in the thread.
I have ordered an F6 and a 24-85 zoom lens, and will be testing this in the future. The most simplified approach may come down to buying a Nikon camera, possibly some of the lower cost DSLR models and using it as light meter. (of course, it can do double duty as a DSLR) A 24-85 zoom matches the composure of .5 normal to 2x normal fl lens of LF. So if the Nikon gives near flawless exposures with 35mm chrome film with a given composure, it should offer the same for LF of the same film type and composure. This assumes you are shooting chromes, are critical about accurate exposure, and shoot in varying lighting conditions....
There is one issue with using a Nikon as a LF light meter.... which I will investigate. You have to be careful of the lens type you use. Lenses with MANY elements often consume more light than a more simple LF lens with typically under 6 elements. Some 35mm lenses have up to 20 elements... I have tested some of my 18 element 35mm lenses, and they consume up to a half a stop of light. Although modern coatings are superb today, they do NOT transmit 100% of light through each surface. Even at 99% transmission per coating, this is 2% loss for each air spaced element. 20 elements = 40 surfaces or 40% light loss. Not all surfaces are air spaced, which reduces the losses a bit. Within a 35mm camera system, this is accounted for, as the light reading is captured at the film plane, already taking into consideration the light transmission losses. Not true with LF, as we don't read the film plane (at least most of us don't, as there is such tools) This is quite easy to test, and the error is always consistent, therefore you can build an easy compensating variable into the Nikon ISO value. Hopefully the Nikon lens I selected will have light losses close to my LF lenses, and it won't be an issue. Just thought I would mention it, as its often overlooked. Older Vintage LF surely have worse transmission values per surface area than modern lenses. Not sure the cut off date, but I would suspect pre 1980 era...
"Even at 99% transmission per coating, this is 2% loss for each air spaced element. 20 elements = 40 surfaces or 40% light loss."
33%, Bill. If you're going to do the arithmetic, do it correctly. 0.99^40 = .669
If you're not going to do the arithmetic, then shoot for calibration. The lens' transmission is, after all, fixed.
Use a 50/1.8 Nikkor, not a zoom. Nice, simple, has as many air-glass interfaces as the typical LF lens. I can't imagine that you, with your passion for perfection, would buy a zoom.
Agreed with your math Dan, this was a simple explanation of transmission losses.... somehow we go from, this entire thread is absurd, and no on needs this level of accuracy...... then to expressing theoretical values down to several decimal places.... sheeeesh...
The point of the matter is, to find transmission losses of a lens, you simply measure the losses, no surface area math required. I get enough slack for too much technical mumbo jumbo, i was trying to keep it lite for discussion purposes...
As for your suggestion of a fixed prime lens for the Nikon.... You missed the point Dan......this has nothing to do with my passion for perfection. The Nikon camera is being used as a light meter, not to capture images. The goal is to match the composure on the Nikon, as seen on the ground glass, this would require a zoom lens, not a fixed fl lens. Re read above.... Make sense now?
I was thinking about this just yesterday, and a thought occurred to me: instead of a light meter, why not use a digital camera? Shouldn't a compact dSLR yield just as good results as a similarly sized and priced light meter, with the added benefit of getting an RGB histogram? Hell, a cheap-o pocket digital with a zoom lens might be just as good as a light meter for exposure metering.
There are of course limitations, mainly that the histogram of all cameras relies on the camera-generated JPEG, instead of RAW data (correct me if you know of an exception here). Whether this creates serious or even discernible deviations in exposure is questionable.
(I didn't read all the 9 pages, so perhaps this has been proposed before.)
The previous "2" pages addressed your concept ad nauseam.
I have come to the conclusion, no one reads a thread before posting :-)
"somehow we go from, this entire thread is absurd, and no on needs this level of accuracy"
Um, Bill, you're the one who insists on absurd levels of precision. Most of us get by being, by your standards, excessively sloppy. I'm glad that you've joined us.
Thanks for explaining why you bought a zoom. Does its range of angles of view cover those of the lenses you'll be using on 8x10?
Cheers,
Dan
> Um, Bill, you're the one who insists on absurd levels of precision.
Yeah, I hear Dan, I'm insane to correct potential 1.3 stop exposure errors when exposing dual 810 color chromes..... call me stupid.... thanks for setting me straight. I have gained a lot from you wisdom. (NOT)
> Most of us get by being, by your standards, excessively sloppy.
I addressed this at least 5x prior.... tired of repeating...please start reading....
> Thanks for explaining why you bought a zoom.
You mean for the 3rd time, right?
> Does its range of angles of view cover those of the lenses you'll be using on 8x10?
I addressed this too Dan.... arggggg....
.5 - 2x normal covers most of my captures on 810, 150mm to 600mm fl's....
Dan, you are always quick to always jump down someones throat. IMO, you can more effectively utilize that time by actually reading the thread, this gets old, real old.
As stated in my OP Dan, if you feel this level of precision, (+/- 1 stop) is more precision in exposure that you would ever require, then stop reading at that point, and move on to another thread. I stated this for a reason, so people like you don't start spear chuck'in, for no apparent reason....other than to waste bandwidth and make a thread so awkward, everyone gives up on it....if that is your motive, you succeed quite often at it.
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