Light metering with gray card indoors with a Canon A1

[james_burnham1]

<p>Hi all,<br>

<br />This website forum has been quite helpful over the years (you turned me on to the Canon 200 FD Macro which is one of my favorite lenses for herpetology photography).</p>

<p>I have a new question. I recently went to Peru with a group. I use a gray card with my 85mm macro (I think that is the size, I'm not at home) outdoors a great deal and have pretty good success light metering with it.</p>

<p>I met up with a group of biologists where we often captured animals at night (mostly frogs) after trying to get in situ shots and then photograph them in a make shift photo hut the next day (then returned promptly to spot of capture). It is a mosquito netted hut with not much for light, and it was pretty dark. I did some flash stuff inside which worked fairly well (I say fairly because the flash sync connector on my A1 doesn't work consistently and often fails completely on me (despite trying several cords/flashes) so I need to put it on the show which isn't ideal).</p>

<p>For the stuff I tried with natural light and metering on the gray card (which with Velvia 50 resulted in long exposure times) I consistently very very very much underexposed the subjects (frogs and snakes will both sit for you, depending on species) to the point of blackness.</p>

<p>I'm seeking some guidance as to why this may be. I think I'm still probably just not "getting" how a gray card works (Despite reading a bunch on it), but perhaps it is something else? Any thoughts?</p>

<p>Thank you in advance.<br>

<br />Jim</p>

[jeffrey_e]

<p>The general advice is to tilt a grey card a bit toward the light source. However grey cards are often a bit shiny. That can lead to the grey card reading as a whole lot brighter than it really is leading to underexposed pictures.</p>

[User_502260]

<p>The idea of using a gray card is that light meters are calibrated for 18% gray. This means that if you meter off of an 18% gray card or a similarly dark mid-tone then the other parts of the scene will all come out as light or as dark as they need to be. Pointing a camera at a bright white object can "fool" the meter. You wil get a high reading because the camera's meter is trying to come up witn an exposure which will render the white objact gray. To compensate for this you would open up 2 stops with print film and about 1.5 stops with color slide film. If it is used properly a gray card is a useful tool for getting the right exposure.<br /> What you are experiencing is called reciprocity failure. If I get a reading of 1/60 at f/8 and I decide I need a faster shutter speed I can go up to 1/125 but then I will have to change my f/stop to 5.6. With many films there is a range, high or low, past which these relationships between shutter speed and f/stop will not work. The problem is more often caused by low light. My meter may tell me I need a shutter speed of 1 full second at f/5.6. If I am using slow film and the light is poor, that shutter speed of 1 full second may have to be extended to 2 full seconds or maybe even 5 full seconds. If I fail to give the extra exposure I may get poor color, underexposure or both. Some film manufacturers give reciprocity failure starting points for correcting exposure and tables are online for various films. The reason we don't see as much reciprocity failure when exposures are too short is that few cameras have top shutter speeds over 1/8000. With automatic flash this can sometimes be a problem.</p>

[jeffrey_e]

<p>Right. Reciprocity failure. Should have thought of that. Yes, long exposure times, slow film will result in reciprocity failure.</p>

<p>I have an idea that Fuji publishes information on exposure compensation in their information sheet on this film.</p>

<p>Wikipedia says this about Velvia:</p>

<h2>Long exposure problems</h2>

<p>The original Velvia (RVP) suffered from <a title="Reciprocity (photography)" href="http://en.wikipedia.org/wiki/Reciprocity_%28photography%29">reciprocity</a> failure much more than other films. Exposing the film for as little as 16 seconds produced a color shift, typically to purple or green, depending on shooting conditions. Anything over four seconds required the use of magenta color correction filters if correct color balance is required, and anything over 32 seconds is "not recommended" by Fuji.^{[<em><a title="Wikipedia:Citation needed" href="http://en.wikipedia.org/wiki/Wikipedia:Citation_needed">citation needed</a></em>]}<br /> Velvia 100 (RVP 100) is much better with long exposures: no reciprocity failure compensation is required for exposures shorter than 1 minute.<sup id="cite_ref-7"><a href="http://en.wikipedia.org/wiki/Velvia#cite_note-7">[7]</a></sup></p>

<p>Here's a link to reciprocity failure chart for Velvia:</p>

<p>http://www.brucepercy.co.uk/blog/2008/05/06/reciprocity-chart-for-fuji-velvia-50-rvp/</p>

[railphotog]

<p>I shot a lot of model railroad photos when I had A-1's. I used Tri-X and Ektachrome 160T. I used a Vivitar 28mm lens in which I mounted a pinhole aperture, and the resulting light gathering ability of the lens was greatly reduced. I found if I just used the camera meter and doubled the time, I got good exposures most of the time. Simple and it worked for me. If the meter read 4 seconds, I set it for 8 seconds and so on.</p>

<p> </p>

[james_burnham1]

<p>Thank you all. I did get some ok (but still darker photos) on some good subjects. I suspect that these are the times where my bracketing went to 2 stops or so either way. This reciprocity issue would explain it.</p>

[awahlster]

<p>This maybe a case where you would be ahead of the game to use a quality handheld meter. And of course to find out what the limitations of your film choice is.</p>

 

Its possible you were outside the range of the A1's meter which with 100 ASA film is only down to F1.4 at 8 seconds. or EV-2 did the meter reading inside the viewfinder blink at you? if so you were outside the range the meter can properly read the light.

[mwmcbroom]

<p>I must strongly agree with what Jeff Adler wrote. He's right on the money.</p>

<p>I'm a little unsure as to how the gray card was being used, which might have had considerable effect on the resultant readings. But I also agree strongly with Mark about getting an external meter. These days you can pick up a high-quality Gossen Luna Pro on the used market for not much money and the dang thing'll give you a light reading value in just about pitch black conditions. If you use a light meter with the incident screen or bulb in place, this simplifies things even more. You just take a reading with the meter located where your subject is, and use that value. Your exposure will be correct, provided there is no bizarre intrusive light source coming from somewhere else.</p>

<p> </p>

[james_burnham1]

<p>I think a light meter will be my next investment. I had been considering it anyway.<br>

Would I use the external meter on a gray card still?</p>

[james_burnham1]

<p>And perhaps this isn't helpful as far as how it was being used, but I set up the shot (we had tables with natural material set ups (leaves, sticks, rocks, etc) on them. I had my camera on a tripod with a flash cord, set everything up with the frog or whatever, then moved the gray card in between the subject and my lense (as close to the specimen I could do so without disturbing it), light metered, set speed/aperture and shot.</p>

[jeffrey_e]

<p>James, there are two basic "flavours" of light meters. (1) Incident light meter which has a "dome". It reads the light hitting the subject. You put the meter next to the subject, point the dome toward your camera, take a reading and you're done. (2) Spot meter which you point at your subject and take a reading just like you do with your camera. With that one you could use a grey card. You need to ensure you're pointing it at something that's neutral grey like a grey card, or alternatively, you need to dial in exposure compensation just like you do now. That type of meter reads the light reflecting off your subject. <br>

<br /> Some advanced meters can do both incident light and reflected light, some can also do flash metering.<br>

Get yourself a simple incident light meter.<br>

Two of the best loved "classic" onees are the Luna Pro and the Sekonic Studio Deluxe. The Sekonic doesn't use batteries and the design dates back to the Norwood Director meter from about the 1940's. I have a Sekonic and it's one of the best photography gizmos I own.<br>

<br /><br /></p>

[mwmcbroom]

<p>James, if you use an external meter that you know is accurate, and set it up to read "incident," which is using the white globe, then all you have to do is put the meter in the same proximity as the subject and take a reading. Set your camera to this value. If the shutter speeds are extremely long, then you're faced with the reciprocity failure that was already mentioned. You might be better off trying to light your scene using indirect flash -- bouncing it off walls or the ceiling -- or colored surfaces to add color to the image. Any of these will reduce harshness of the flash's light. And to make sure that your exposure is accurate, a flash meter is good for this. They aren't nearly as expensive as they used to be -- or you might know somebody who has one you could borrow, if funds are tight.</p>

<p>Because of your subjects, it seems to me that you would prefer flash, to freeze movement. The sparkle in a subjects eye that flash can provide is important too, I feel. So if I were you, I would be working toward the goal of improving my flash pictures. As for your flash sync connector problems, get a hot-shoe mounted flash sync module for flash PC cords. Just one with a single center contact is all you need. They're relatively cheap and useful for situations like this.</p>

<p> </p>

[james_burnham1]

<p>"get a hot-shoe mounted flash sync module for flash PC cords. Just one with a single center contact is all you need." </p>

<p>Thanks, I've tried that twice (bought two), never been able to get them to work... I'll give it another shot... probably just old / broken gear. <br>

<br />The incident meter gives me some pause/concern as I have to place it near the subject. When I'm dealing with frogs / snakes I can't put something too close to the animal as it will get them moving. Plus, when I'm dealing with venomous snakes that has another issue. But I'll give it some thought.<br>

Thanks for your input. (That is to everyone).</p>

[jeffrey_e]

<p>EIther put the incident meter someplace that has the same light as your subject or take a meter reading using your camera or a hand held spot meter from a distance. One trick that works pretty well using your camera's meter is is to take ameter reading off the palm of your hand and open up one stop. I'm assuming your hand will be more or less lit the same way as the subject of your shot.</p>

[james_burnham1]

<p>actually, nevermind, i've been trying these <a title="Flash Hot Shoe Adapter for PC Sync with Cord" href="http://www.ebay.com/itm/Flash-Hot-Shoe-Adapter-for-PC-Sync-with-Cord-/350714848409?pt=Camera_Flash_Accessories&hash=item51a83be499">Flash Hot Shoe Adapter for PC Sync with Cord</a><br>

since the sync button doesn't work, neither have these... <br>

I'll get the other type of sync module<br>

thanks.</p>

[mwmcbroom]

<p>Hey James,<br /> As long as your gray card was evenly lit in the scene, your metering should be spot on. Assuming the meter you're using is accurate, of course. You don't have to get the incident meter up next to the subjects, just in an area that is receiving the same light value as the subject, and approximately the same distance from the camera as the subject.</p>

<p>If the flash sync adapter shown in your link is not working on your camera, then your camera has problems. Well, the quality of stuff coming out of China being what it is, if you have a multimeter or a continuity tester, you might want to touch the contacts on each end to make sure you have continuity. If you don't, then the adapter is the problem. If you do have continuity, then obviously, your camera is at fault.</p>

<p> </p>

[mwmcbroom]

<p>Sorry, I didn't realize that you were using the wrong type of flash sync before this forum's edit timer ran out on me. You need a flash sync module that has a hot shoe contact. Like this one, for example: http://www.ebay.com/itm/160974602407?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649</p>

[feanolas1]

<p>Maybe you could setup and mesure the scene before the subject is placed in it. Thus you can make a precise metering and avoid getting bitten!</p>