 |
 | Home | Contact Us | FAQ | Search & Site Map | Link to Us |
 | Sign In | Join | Other 45 Sites in Network |
| PhotoKB HomeDiscussion Groups Digital Photography Digital PhotoDSLR CamerasZLR CamerasPoint & Shoot CamerasFilm Photography 35 mmLarge FormatMedium formatDarkroomFilm and LabsOther EquipmentPhoto Technique Nature PhotographyPeople PhotographyTechnique GeneralGeneral Photo Topics General TopicsAustralian PhotographyUK PhotographyDirectoryPhoto Clubs |
Photo Forum / Film Photography / 35 mm / July 2006light meter tests
My light meter tests 18% gray card reflection of sky light, 9:30 - 10:00 AM, high sun behind thin high clouds, bright enough. ISO 100 set for all meters: Pentax K2/50mm F/2 18%: 125 F/8 (spd) Soligor Spot- 18%: 125 F/8 +2/3 sensor II (spd) Sekonic L-28c2 18%: 125 F/11 +1/3 Lumigrid in, high slide out (selenium, 70's) Sky: 125 F/11 Lumisphere in, high slide in Brockway M2 18%: 100 F/13 Photogrid in, high slide out (selenium, 50's) Sky: 100 F/11 Sphere in, high slide in Sekonic L-162 18%: 125 F/11 +1/2 front closed, slit read (selenium, 60's) 18%: 125 F/8 front open (booster closed for both) I bought the K2 used recently, did put one roll of gold 100 through just to see how the shots would come out staying straight with it's meter readings, nothing special. They came out like "perfect", using the super market's kodak service. As a result I am confused as a non expert. Anyone know what I should trust in the above meters? All the selenium readings came out different and averaging the same. Let's say; use the mint condition L-28c2 as a standard for the selenium meters because there could not possibly be anything wrong with it -- so I don't get it. Any advice much appreciated, directives? Orders?  Signature}<)))*> Giant_Alex cravdraa_at-yahoo_dot-com not my site: http://www.e-sword.net/ My light meter tests Please don't use html in news groups Please don't use html in news groups OK, I did't (I think), I used "rich text" so the font would be what I want, non proportional courier new. What damage does it do? AAvK > Please don't use html in news groups > > OK, I did't (I think), I used "rich text" so the font would be what I want, > non proportional courier new. What damage does it do? > AAvK It makes your post hard to read. There are other things, too, but too complex and beyond the scope of this course..... Please just use plain text on usenet! SignatureJohn McWilliams > It makes your post hard to read. There are other things, too, but too > complex and beyond the scope of this course..... I didn't know that, but then again, I can read it perfectly fine. > Please just use plain text on usenet! OK, I will! Signature}<)))*> Giant_Alex cravdraa_at-yahoo_dot-com not my site: http://www.e-sword.net/ >My light meter tests >18% gray card reflection of sky light, 9:30 - 10:00 AM, >high sun behind thin high clouds, bright enough. >ISO 100 set for all meters: ------------------------------------------------------------ Doesn't surprise me in the least. Whenever I do checks such as this, I've had variations such as yours unless I'm only comparing equipment from one manufacturer. (Just try it with a matrix metered body!) Have you seen the difference in price between log response photo meters such as you've tested and linear meters as used by lighting engineers? Could be a clue. SignatureM Stewart Milton Keynes, UK -- Posted via a free Usenet account from http://www.teranews.com > My light meter tests > Pentax K2/50mm F/2 18%: 125 F/8 [quoted text clipped - 5 lines] > ... -- so I don't get it. ... > Any advice much appreciated, directives? Orders? That's about as good as it gets. Settle on using one meter and calibrate your effective ASA/developing for that combination of camera/meter/film/processing. Exposure to 1/3 of a stop is only needed (maybe) for Kodachrome slides and gnat's arse black and white work. For color negative anything within 2 or 3 stops is good enough if the error is towards overexposure. For B&W being within a stop is golden. After the metering test, realize everything else has a tolerance: Aperture- f2.0 is most likely closer to f2.4, f2.8 is around f3.0 and the aperture will change with temperature and how the diaphragm is closed - auto or manual, from which side, how long since you used the lens, has any oil got on the blades or mechanism ...; Is the aperture in the 'click' or riding up one side; Shutter - a mechanical shutter is only good to 1/3 of a stop and again changes with use and temperature; The real speed of the film Vs what it says on the box - another 1/3 of a stop; How fresh is the developer; If the film was frozen how long has it been unfrozen before it was developed; And most commonly - was the meter read correctly, was the ASA set correctly, were the readings transferred to the camera without error, was a finger/case/strap in front of the meter cell ....? Take pictures, if the results are OK for you then the equipment is also OK. > **** > *My light meter tests* [quoted text clipped - 32 lines] > ** > *Any advice much appreciated, directives? Orders?* Most of the other answers are right in that different meters will rarely agree with each other. My own meter tests usually yielded even greater differences than yours. Also, older selenium meters may often have dodgy cells (usually depending on how much light they have been exposed to - a good light-tight case is significant here). That said, some older selenium meters are still my references... Decide which meter gives *you* the best results and use that as a reference. > AAvK wrote: > [quoted text clipped - 38 lines] > cravdraa_at-yahoo_dot-com > not my site: http://www.e-sword.net/ That's about what you would expect with meters of different types. If you take f/11 as the reference, then your variations are minus one stop (f/8), and plus 2/3rds stop (f/13). With age, selenium meters tend to read low, leading to overexposure, and CdS meters (I think the Pentax uses a CdS) can be sluggish, especially going from bright to less bright light. I think Pentaxes used mercury batteries at 1.3 volts, now unavailable. Substituting an alkaline or lithium battery will cause the readings to be way off. If as you say the light was almost full sunlight, I would expect the exposure to be 1/125 at about f/11 to f/13, based on the sunny f/16 rule. Colin D. SignaturePosted via a free Usenet account from http://www.teranews.com > > AAvK wrote: > > [quoted text clipped - 47 lines] > unavailable. Substituting an alkaline or lithium battery will cause the > readings to be way off. Agreed, this is about the range one expects with older meters. For info. though, the OP is correct that the Pentax K2 uses a Silicon Photo Diode, not the CdS. Also, it runs off two 1.5 Volt silver oxide (or alkaline) batteries. Pentax has tended to use a bridge circuit for its meters, so they are much more immune to voltage variation than most cameras - sufficiently so that the old Spotmatics designed for mercury batteries will give identical readings when a modern silver oxide battery is substitued. It surprises me that the K2 is reading so differently from all the others. The variation within all the selenium meters is exactly par for the course, but I wouldn't expect an SPD cell to be so far from the mean - possibly as it has a centre weighted pattern while all the seleniums listed are integrative and the Soligor is spot meter there is some aspect of metering technique making the difference? > If as you say the light was almost full sunlight, I would expect the > exposure to be 1/125 at about f/11 to f/13, based on the sunny f/16 > rule. Based on the conditions as described, I'd have estimated about f8 2/3 to f11, not very different to your guess. Peter > If as you say the light was almost full sunlight, I would expect the > exposure to be 1/125 at about f/11 to f/13, based on the sunny f/16 > rule. Using anything other than the classic Pentax Spotmeter V is totally and utterly foolish. I find mine to be killer and spot on! Rita > > If as you say the light was almost full sunlight, I would expect the > > exposure to be 1/125 at about f/11 to f/13, based on the sunny f/16 [quoted text clipped - 4 lines] > > Rita They're good, but not the only good meter. F'rinstance they can only do spot readings. A meter like the Sekonic L-508 or better can do spot, incident, reflected, and flash readings, much more versatile than a simple spot meter, and it's accuracy is down to 1/10 stop - which is somewhat pedantic I guess, but nice to know. For shooting digital, incident measurement is excellent, as it guards against blown highlights better than other methods. My major concern with spot meters, and the reason I sold my pentax V, is that unless you can use a gray card to meter your shots, you have to guess what part of your scene is 18% gray if you want an accurate reading. I used to end up measuring the brightest and darkest areas of interest and averaging the readings, but by then the subject had gone home and the sun was setting (figuratively). I can't understand the enthusiasm for spot meters, like one of the points touted about the D70 over the 350D and 20D is spot metering, but careless or poorly understood use of spot readings can lead one astray very easily, more so even than a general or centre-weighted reflected reading. Take a typical wedding, for example. Bride in white, groom in black morning suit, bridesmaids in gamut-threatening colors, red brick church, etc., what are you going to use for your spot reference? Ask the bride to hold a gray card? Incident metering solves all this hassle. YMMV, Colin D. SignaturePosted via a free Usenet account from http://www.teranews.com . Take a typical wedding, for example. Bride in white, groom in > black morning suit, bridesmaids in gamut-threatening colors, red brick > church, etc., what are you going to use for your spot reference? Ask [quoted text clipped - 3 lines] > Colin D. > Posted via a free Usenet account from http://www.teranews.com Who cares what the reading is? The ambient light should be behind the B/G. The main light should be from the flash, and the most usable GN should have been figured out a long time ago. Bob Hickey > > > If as you say the light was almost full sunlight, I would expect > > > the exposure to be 1/125 at about f/11 to f/13, based on the [quoted text clipped - 16 lines] > guess what part of your scene is 18% gray if you want an accurate > reading. Well, really you are not looking for which bit of the _scene_ equates to 18% grey, but to which bit of it you _want_ to equate to 18% grey in the finished image. They may be the same, but they may not. Or the need to preserve either highlights or shadows may mean that the '18% point' (or Zone V, if you want to call it that) of the scene simply can't be used as the '18% point' of the image as shot, though it can be moved there in processing/printing later. Now, if you're shooting something with a more or less known tonal range, which will fit your film/sensor's dynamic range, and where the object is to keep the image as much like a straight record, rather than an artistic interpretation, as possible - a wedding shot, for example - then you are indeed better off just going with a single incident or grey card reading. But when you want to control the image to produce something more interpretative, or where the tonal range is just too big, then a spot meter is invaluable. Peter (Uses a Sekonic L-608, mostly) > 18% gray card reflection of sky light, 9:30 - 10:00 AM, A few comments: 18% gray as "middle gray" is a myth. Read about it, there is plenty of good info about it out there. 13% (or actually a bit less than that) is closer to "middle" gray. Ansel Adams is to blame for that :-))) Light meters are not calibrated using gray cards but using special light sources. Angle of measurement matters with reflected light and your differences can be accounted for by a different angle used by different meters (assuming all meters were set/calibrated to the factory specs...) How you hold the meter in relation to the surface of the card matters, too. >did put one roll of gold 100 ... >They came out like "perfect", using the super market's > kodak service. Test with slide film using color charts - C41 negative is useless for exposure accuracy testing. With color, you want the "proper" density, highlight and shadow detail and color "accuracy" (note the quotes...) With B&W you want the first two plus the "proper" gray scale rendition of colors. All 3 factors are/can be affected by exposure among other things so run your "personal EI tests" using a selected film and process, one meter and one camera/lens. ><eM eL>< Thanks for the reply and good pointers! > A few comments: > 18% gray as "middle gray" is a myth. Read about it, there is plenty of good > info about it out there. 13% (or actually a bit less than that) is closer to > "middle" gray. Ansel Adams is to blame for that :-))) > Light meters are not calibrated using gray cards but using special light > sources. hhmph... I read that the card is about reflecting 18% of the 'light' that is there, this then becomes a proper reading. Nothing about the factor of 'middle gray' as a reading. But that 'middle gray' reflects 18% of the light, the light itself being the point for the reading. But I will study-up on gray card reading! > Angle of measurement matters with reflected light and your differences can > be accounted for by a different angle used by different meters (assuming all > meters were set/calibrated to the factory specs...) > How you hold the meter in relation to the surface of the card matters, too. I just used a straight 90º angle, like at a foot and a half away or so and no shadow allowed. Unless it was closer for the camera so the card would fill the frame. But the card was not exactly facing the sun either, but straight up to the sky at the time in the morning that I stated earlier. >>did put one roll of gold 100 ... >>They came out like "perfect", using the super market's [quoted text clipped - 7 lines] > "personal EI tests" using a selected film and process, one meter and one > camera/lens. That was only about seeing some shots come from the new/used camera, not quite the scientific point just yet, just to see how it all goes, including the light meter in it. However, thank you for that lesson on what to do. >><eM eL>< Signature}<)))*> Giant_Alex cravdraa_at-yahoo_dot-com not my site: http://www.e-sword.net/ > **** > *My light meter tests* [quoted text clipped - 21 lines] > *I bought the K2 used recently, did put one roll of gold * > *100 through just **to see how the shots would come out * Negative film (100 Gold) is not a "reference" means of evaluating metering. Use slide film such as Sensia 100 (neutral) for "middle" evaluation (12-13%) and the higlights will lose detail at about +1.7 to 2 stops higher with shaddows rolling off dead black at -1.5 to -2 stops. With negative film you can over expose by over a stop and the prints will be well corrected. > *All **the selenium readings **came out different and averaging * Selenium meters do change over time; newer meters are stable over time. Meters are all a little different due to their design and calibration standard (manufacturer) but on the whole lie close enough to the 12-14% grey point (not 18%). Cheers, Alan. Signature-- r.p.e.35mm user resource: http://www.aliasimages.com/rpe35mmur.htm -- r.p.d.slr-systems: http://www.aliasimages.com/rpdslrsysur.htm -- [SI] gallery & rulz: http://www.pbase.com/shootin -- e-meil: Remove FreeLunch. |
Reply to this Message |
 Sign In
 Join
 My Latest Posts My Monitored Threads My Blog My Photo Gallery My Profile My Homepage Start New Thread Enable EMail Alerts Rate this Thread
|
©2008 Advenet LLC Privacy Policy - Terms of Use
This website includes both content owned or controlled by Advenet as well as content owned or controlled by third parties.