Center weighed meter accuracy

[julien_boudreau]

<p>Hello,</p>

<p>I just purchased a FM2n as I'm looking to get into B&W film and develop the negatives myself. This being said, I don't have all the equipment yet so I've been shooting Illford C41. When I bought the camera, I had it tested and seals redone (covered by warranty, so free). I was told that the meter was underexposing by about 1/2 a stop, and that I should compensate with my ASA/ISO dial.</p>

<p>Given this, I set out to shoot with the C41 400, but my ASA set to 320 (approximately). All my images came out incredibly flat - the shadows and highlights very close to the neutral 18% - the images were just a mess of grey. I was able to recapture the images in Photoshop once the negatives were scanned, but I would rather know how to use the FM2n meter properly.</p>

<p>I apologize if this has been asked too many times, but I'm specifically wondering if my ASA compensation might have to do with this. I'm not sure, now that I've shot a few rolls, if the meter actually underexposes or if I did something completely wrong. The lighting was quite harsh that day. </p>

<p>How can I get proper contrast outdoors using a Center Weighed meter, such as the one in the Nikon FM2n. What's the best way to use a center weighed meter? I can't really place elements in the Zone system as that would require a spot meter to do properly.</p>

<p>Should I get it tested again?</p>

<p>Thanks,</p>

<p>J</p><div></div>

[john_shriver]

<p>You need to look at the negative by eye, with "known well exposed and processed" negatives as a reference.<br>

But, if you're scanning the negative, it may be a matter of scanning technique. Use the histogram feature of your scanning software, and slide the white and black points to just come to the ends of the histogram.<br>

If the histogram takes up a reasonable part of the available horizontal range, and is well-centered, you're probably exposing fine. If it's scrunched up to the black side, you're underexposing. If it's scrunched up to the white side, you're overexposing. (This assumes that the scanner is set to scan negative transparencies. Otherwise swap black and white.)</p>

 

[julien_boudreau]

<p>Thanks...it's what I've been doing in photoshop. The histogram is focused near the middle, so I'm bring the blacks and whites to the image's starting balck and white values.</p>

<p>This was scanned by a photo lab in town, although they don't do much film these days...</p>

<p>J</p>

[SCL]

<p>The easiest is to take a reading on a bright clear sunny day of a grey card and see how it compares to the sunny 16 rule. If you're within about a half stop you should be ok as the film tolerances will generally pick up any slop. You could likewise compare readings against a known good meter. The zone system really only works when you're exposing and developing your own film, having run test shots to calibrate your gear. You certainly can use center weighted metering for Zone measurements, you just have to be precise in your metering of objects. Having said that, it sounds like the processing of your film is probably the source of your problem, unless you are inadvertantly not metering properly. On the day of the questionable roll, although the lighting was harsh, you were measuring reflected, not incident light. Were your SUBJECTS contrasty, that is did they have a wide range of tones within them even if the light was intense? Did you expose per your meter or apply additional compensation? If the subjects had a range of tones, and you exposed per your meter readings, the issue is probably poor development....exhausted chemicals.</p>

[julien_boudreau]

<p>The subjects had lots of contrast, indeed. Which is why I was shocked when I saw the scanned negatives. I metered the subject and had my meter either reading 0, 0+ or 0- . It's an LED meter for those of you who havn't used one. So all within the meter's range.</p>

<p>J</p>

[bgelfand]

<p>Just looking at the picture you posted, I would have guessed either you were trying for a high-key shot or were over-exposed.</p>

<p>Since you are shooting a landscape (which does not move or change in a short period), I suggest you try bracketing. Set the light meter to the film box ISO - 400. Now shoot a frame, Next open one stop, but keep the shutter speed the same and shoot another frame. Next close down one stop from the lightmeter reading (two stops from your one over reading and shoot another frame. See which one you like and set the ISO accordingly. Be aware of any change in light due to clouds while you are conducting this test.</p>

[julien_boudreau]

<p>well, it seems considerably overexposed! But the odd thing is that there are no whites. Overexposing...wouldn't that result is some somewhat "blown" highlights?</p>

<p>J</p>

[thirteenthumbs]

<p>EI 320 is only 1/3 stop more than ISO 400 so you will notice very little difference on the film. If you had exposed at EI 250, +2/3 stop, you would have noticed more near blown highlight.</p>

<p>Looking at your posted image in Photoshop- Levels- the highlights start at 247 but there is not much information until 232; shadows start at 13; then moving the midtone slider from 1 to .83 improves the overall contrast well. Your negative/scan has a lot of detail as it should.</p>

<p>Where you point the center of the viewfinder will influence your reading. Point it at the sky and take a reading, point it at the deepest part of the shadows and take another reading. The two readings should be several stops apart. Set your exposure to where you want your mid point to be.</p><div></div>

[julien_boudreau]

<p>Thanks. I managed to get some "decent" images in photoshop correcting the levels, just surprised at the lack of contrast in the negative. In the end, I'd love to have good contrast from the film, and not rely too much on Photoshop.</p>

<p>This being said, I don't think I need to adjust my ASA for the meter's underexposure - I was told it was 1/2 a stop at most, so it might be almost insignificant.</p>

<p>Again, trying to get proper negs as a learning exercise, although I can easily manipulate in Photoshop.</p>

<p>Thanks for all the advice.</p>

<p>J</p>

[randy_johnson5]

<p>This seems like too little development time to me. Check your developing procedures and developer dilutions also. Are you agitating 5 sec every 30 sec during development?</p>

[thirteenthumbs]

<p>It is very possible that this film was slightly under developed. If you told the lab that you exposed the film at a different EI/ISO they might have pulled the development by 10% without asking you first. Due to a slow down in C41 processing the labs chemicals may be getting weak due to age, not volume. If the results consistently show gray highlights then increase exposure by 1/4 to 1/2 stop via the aperture of your lens, exposure compensation dial, ISO setting, or a combination of two of the 3. </p>

<p>Experimenting with a gray card, metering it with the light hitting it at different angles, with the card in the same basic position will help also (card in bright sun, reflecting light toward the meter, not reflecting light toward the meter; same in open shade and deep shade).</p>

[julien_boudreau]

<p>Well...if it's under developed, it wouldn't explain the darks being gray. It seems like everything was overexposed, and they underdeveloped as well. It was done by a photo shop in the city, but I doubt they do much film these days. Anyways...soon I'll have the equipment to develop my own, and hopefully a decent scanner. They did a poor scanning job too.</p>

<p>J</p>

[lachaine]

<p>Some are obviously not reading the question. This is C41 process XP2 film. It behaves completely differently than traditional black & white film. You don't really play with development time when using XP2.</p>

<p>I'll go out on a limb and play devil's advocate, but this may actually be the opposite of overexposure. We're talking a scan from a C41 process lab. I suspect this may actually have been severely underexposed due to relying on uncompensated centre-weighted metering on a very bright scene, and then the scanning process tried to correct it - as if it were colour film. XP2 has extremely wide latitude, and you can expose as anywhere from ISO 200 to 800, within the same roll of film, without any change in development whatsoever -- and all the pictures would look good. But XP2's extreme exposure latitude is more towards overexposure than underexposure. It can produce terrific B&W pictures... really outstanding B&W with virtually zero grain and georgous creamy whites. But you have to start with a scan that was not corrected as part of the scanning process. I would suggest this negative could be recovered by re-scanning from scratch and then working it up in a image editor - preferably using a 48-bit TIFF file. The scan you have right now is probably not the best to work with, especially if it's a JPEG that's already been corrected (or attempted correction).</p>

<p>All in all, I very much doubt that slight over or underexposure due to meter inaccuracy would make any significant difference with film such as XP2. It would have to be more like severe underexposure due to not using centre-weighted metering effectively.</p>

[julien_boudreau]

<p>Pierre - it does seem to be underexposed, and then "corrected" to brighten it. This being said, I don't know how this would have happened. My meter was set to 0 or 0+ on every shot, and my ASA was 320 - not far from 400.</p>

<p>I really appreciate you guys taking the time for this.</p>

<p>J</p>

[dhbebb]

<p>It is hard to draw conclusions without being able to see the negs, but I would suspect first and foremost underexposure, which is guaranteed to give low contrast with color neg films and chromogenic b+w (i.e. all C41 films). I would routinely cut the box speed of all C41 films in half (e.g. 400 down to 200) - if your meter is reading 1/2 stop too high, factor that in too and set your film speed dial to 125. Nikon center-weighted metering is the best of its kind (I own numerous F3s and an FM3a) and is easily accurate enough for negative material, although you might find it is biased towards landscape format pictures. If you meter a landscape scene and get different readings for a horizontal and vertical picture, go with the horizontal reading. <br>

If you follow the above suggestions and still get flat negs, then and only then suspect tired C41 chemistry, light fogging during processing, or old and/or poorly stored film.</p>

[julien_boudreau]

<p>One thing I don't fully understand...</p>

<p>If it's underexposed, wouldn't I have dark shadows with very little detail? What's strange is that the shadows AND the highlights are almost in the neutral range - and maintain a lot of detail.<br>

Either way...I think the store I had them done has issues.</p>

<p>J</p>

[Alan Marcus]

<p>Checking the calibration of a meter, built-in or hand held is tricky. Since the proof of the pudding is in the eating, you should shoot a series using the ISO setting of your meter to make the adjustment. I advise shooting the series in 1/3 ISO increments. Better to keep the shutter speed constant and adjust the lens aperture when making the series. </p>

<p>Print or have prints made and visually evaluate. Additionally, I advise including a gray card prominently in the scene. The image of the gray card should be large so that it can be measured using a densitometer. Have your friendly photo lab that uses a densitometer daily, read a clear area of the film and the center of the gray card image. Most friendly labs will do this free.</p>

<p>A proper reading for the gray card on black-and-white film is 0.75 density units as read via the visual (yellow) filter of the transmission densitometer. You're properly exposed and processes film read 0.75 plus the value of the clear film. An example: clear film reads 0.10 then the gray card likely will read 0.85.</p>

<p>You should read all the rames in the series to get a handle on how changing the ISO increase or decrease density. I think, due to the variables of the meter, the process, the film manufacturing etc. the best you can expect is 1/3 stop accuracy. A typical 1 f/stop under reads about 0.50 plus clear film. A typical 1 stop over reads 1.00. A 1/3 stop change, expect about plus/minus 0.24 density units. These readings vary deepening on film contrast.</p>

[dhbebb]

<p><< One thing I don't fully understand...<br>

If it's underexposed, wouldn't I have dark shadows with very little detail? What's strange is that the shadows AND the highlights are almost in the neutral range - and maintain a lot of detail.<br />Either way...I think the store I had them done has issues.>><br>

If you have full shadow detail and low contrast, then the cause can be a very dirty lens (or filter) or else a foul-up during processing. I would judge your results by optical prints from the negatives - trying to figure out what is going on from scans of your negs is just introducing too many unknown variables at once.</p>

[simon_crofts]

<p>If you have a digital camera handy, or have a friend who has one, you can check the accuracy of your FM2n meter very easily.</p>

<p>Take both cameras, set the same ISO, and the same aperture, in manual mode. Set the digital camera to centre weighted for consistency's sake. Point them at a blank, evenly lit wall, preferably a white-ish wall (though that's not critical) in decent lighting conditions eg. lit by indirect sunlight where the sun isn't popping in and out behind clouds.</p>

<p>Take a picture with the digital camera. Check the histogram. It should be tightly bunched right in the centre of the graph. If it isn't, then your digital camera meter is out, and adjust the shutter speed to whatever is necessary to bring the histogram to the centre.</p>

<p>Now point your FM2n at the same wall (making sure that nothing in the lighting has changed). See what shutter speed the meter recommends you set. It should be the same as that on the digital camera after correction. If not, then you the difference is the adjustment that you have to make.</p>

[simon_crofts]

<p>The scan looks overexposed. It may just be the quality of the scan, or it could be that the negative is overexposed. That's pretty hard to do with XP2 though.</p>

<p>Did you try sticking a new battery in the meter? It could just be that it needs replacing.</p>

 

[julien_boudreau]

<p>New batterie is in, yes.</p>

<p>But under or over developed would still have a larger range of tones, no? It seems that 80% of the image is neutral gray. I'll test it against my D90.</p>

<p>Thanks,</p>

<p>J</p>

[simon_crofts]

<blockquote>

<p>But under or over developed would still have a larger range of tones, no? It seems that 80% of the image is neutral gray.</p>

</blockquote>

<p>Whether it's over- under- exposed doesn't per se affect contrast. Contrast of the scene remains the same.</p>

<p>When you're getting flat contrast in the negative, with a lack of information in either the highlights or the shadows, it's just a symptom that the film may have been exposed beyond its dynamic range in one direction or the other so that information in the highlights or shadows are beyond the capabilities of the film and have been lost.</p>

<p>XP2 has inherently extremely low contrast, so that when scanning it the operator will need to boost contrast eg. via levels so that the result isn't extremely dull to look at. But in the JPEG you posted it goes beyond this, because there seems to be a lot of detail in the highlights that have been lost. That may have been due to overexposure of the film, or it may be due to bad scanning or bad development, or a mixture of those.</p>

<p>If you look at the negative and the negative doesn't seem unduly dark or unduly light, but rather somewhere in the middle, then the meter did a good job, and the scene was lowish contrast and/or XP2 has low contrast anyway - it takes a very contrasty scene before the the negative starts to look very exciting.</p>

<p>The wall test I mentioned above ust takes a few seconds and will tell you for sure whether the camera meter is accurate or not.</p>

 

[julien_boudreau]

<p>Thanks,</p>

<p>I'm doing a wall test this evening with my D90. Also, contacted the local camera shop. He's going to properly test my meter, again. He'll also take a look at my negatives as he's a very experienced B&W developer and printer. This will be very helpfull.</p>

<p>There seems to be information in both the highlights and shadows, although it's all in the mid gray zone. It's like the entire image only captured 3 zones.</p>

<p>Again, I really appreciate the help.</p>

<p>J</p>

[simon_crofts]

<blockquote>

<p>There seems to be information in both the highlights and shadows, although it's all in the mid gray zone. It's like the entire image only captured 3 zones.</p>

</blockquote>

<p>If the tones are in the mid-range then it sounds like the meter's working OK then (though do check it against the D90 to get a precise answer), it's probably just XP2's inherent lack of contrast, and that they did a less-than-great scan.</p>

[julien_boudreau]

<p>Thanks,</p>

<p>I'm doing a wall test this evening with my D90. Also, contacted the local camera shop. He's going to properly test my meter, again. He'll also take a look at my negatives as he's a very experienced B&W developer and printer. This will be very helpfull.</p>

<p>There seems to be information in both the highlights and shadows, although it's all in the mid gray zone. It's like the entire image only captured 3 zones.</p>

<p>Again, I really appreciate the help.</p>

<p>J</p>