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#11
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digital camera as exposure meter
On Aug 8, 12:48 am, viewerofrecphoto wrote:
I'm most interested in a dynamic range check. For exposure, I usually use a gray card or my hand, with the built-in full frame meter. I'd like to see how far out the sky is, without pulling out my spot meter and taking several readings. If that's what you want, a digital camera isn't that good at it. Histograms aren't marked in stops and, even by loading special white balance settings and tone curves into my D200 (*), the histogram isn't anywhere near being reliable except to judge distance from highlights clipping. That is: I could not calibrate the lower end of the histogram to be able to read off the distance from the darkest to the brightest points. A spotmeter is better for this. Personally I use my camera's spotmeter and take 2 readings in aperture priority (the digital scales appearing in manual mode only show up to 3 stops + or minus, so it takes less wheel-turning to switch to aperture priority, do this, and switch back to manual) to estimate DR. I don't think it's slower than snapping a shot and looking at the histogram, even if that worked. (*) Note that in-camera histograms are produced from a jpeg, not the raw data, and so is affected by white balance, tone-mapping and other settings; so you need to calibrate for a particular set of those if you want to use it as an accurate lightmeter, as I sometimes do. |
#12
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digital camera as exposure meter
If you are thinking about buying a digital camera for this purpose I would
not waste the money. However experimenting with what you have is another matter. You will get more accurate results with a high end exposure meter properly. This is true whether shooting film or digitally. The incamera histogram tells you absolutely nothing about whether you have captured the details you are looking for in the shadows and highlights. Ditto for the LCD screens built into dSLRs as they cannot resolve enough detail and brightness levels to tell you anything of value. Because of their small size the screens are often misleading about whether you even had proper focus for the shot. This is a major drawback of EVF cameras with which it can be difficult to even achieve critical manual focus on a tripod. Film, negative in particular, has more latitude than digital. Hence I suspect the results of a digital histogram will not be worth the waste of battery power as the results will not translate into information captured on film. |
#13
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digital camera as exposure meter
Recently, viewerofrecphoto posted:
On Aug 7, 1:22 am, Noons wrote: now, this baffles me. the histogram is really not mandatory for exposure metering. it is useful mostly for dynamic range and colour balance checking, particularly the rgb histogram variety. Are you absolutely sure you are not after a colour temperature meter? I'm most interested in a dynamic range check. For exposure, I usually use a gray card or my hand, with the built-in full frame meter. I'd like to see how far out the sky is, without pulling out my spot meter and taking several readings. Since you have a Minolta spot meter, I'm also puzzled as to why you don't just use it? As has been mentioned, the response of digital sensors differs from film. So, "...how far out the sky is..." is likely to be misleading. Of course, you might be able to learn how to read the response differences, and in that case "any old" digital camera would probably suffice. Neil |
#14
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digital camera as exposure meter
viewerofrecphoto wrote:
On Aug 7, 1:22 am, Noons wrote: now, this baffles me. the histogram is really not mandatory for exposure metering. it is useful mostly for dynamic range and colour balance checking, particularly the rgb histogram variety. Are you absolutely sure you are not after a colour temperature meter? I'm most interested in a dynamic range check. For exposure, I usually use a gray card or my hand, with the built-in full frame meter. I'd like to see how far out the sky is, without pulling out my spot meter and taking several readings. If you're shooting film, esp. slide, the spotmeter is _the_ way to go. -- -- 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. |
#15
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digital camera as exposure meter
"gowanoh" wrote:
If you are thinking about buying a digital camera for this purpose I would not waste the money. However experimenting with what you have is another matter. You will get more accurate results with a high end exposure meter properly. This is true whether shooting film or digitally. An external exposure meter is almost totally worthless in conjunction with a decent DSLR. (For that matter, the in camera light metering isn't all that necessary either.) The incamera histogram tells you absolutely nothing about whether you have captured the details you are looking for in the shadows and highlights. Actually it does tell pretty much what you've caught in the highlights. Shadows analysis takes a bit more, but not much. (Use the histogram or the blink-on-over-exposure LCD display to set highlights; then use the camera's spotmeter to measure the shadows. That technique does require experimenting to know exactly how far down from the actual exposure the shadows can be for whatever level of detail is acceptable to the photographer.) Ditto for the LCD screens built into dSLRs as they cannot resolve enough detail and brightness levels to tell you anything of value. Because of their small size the screens are often misleading about whether you even had proper focus for the shot. With a good DSLR the LCD image can be magnified several times, allowing analysis of focus. (That is cumbersome, and I have never bothered to actually do it, but for photographing static scenes it should work just fine.) This is a major drawback of EVF cameras with which it can be difficult to even achieve critical manual focus on a tripod. Film, negative in particular, has more latitude than digital. Hence I That isn't true for current DSLRs. suspect the results of a digital histogram will not be worth the waste of battery power as the results will not translate into information captured on film. That might be the case. On the other hand if the photographer understands the technology it can be of significant value. I'm not sure the significance equals the price of a good DSLR for a person who wants to shoot film though... But certainly one instance would be for medium or large format film users. A DSLR would stomp all over using a Polaroid. -- Floyd L. Davidson http://www.apaflo.com/floyd_davidson Ukpeagvik (Barrow, Alaska) |
#16
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digital camera as exposure meter
Floyd L. Davidson wrote:
"gowanoh" wrote: If you are thinking about buying a digital camera for this purpose I would not waste the money. However experimenting with what you have is another matter. You will get more accurate results with a high end exposure meter properly. This is true whether shooting film or digitally. An external exposure meter is almost totally worthless in conjunction with a decent DSLR. (For that matter, the in camera light metering isn't all that necessary either.) The incamera histogram tells you absolutely nothing about whether you have captured the details you are looking for in the shadows and highlights. Actually it does tell pretty much what you've caught in the highlights. Shadows analysis takes a bit more, but not much. (Use the histogram or the blink-on-over-exposure LCD display to set highlights; then use the camera's spotmeter to measure the shadows. That technique does require experimenting to know exactly how far down from the actual exposure the shadows can be for whatever level of detail is acceptable to the photographer.) Ditto for the LCD screens built into dSLRs as they cannot resolve enough detail and brightness levels to tell you anything of value. Because of their small size the screens are often misleading about whether you even had proper focus for the shot. With a good DSLR the LCD image can be magnified several times, allowing analysis of focus. (That is cumbersome, and I have never bothered to actually do it, but for photographing static scenes it should work just fine.) The D200 is easy to zoom in to more than 100% magnification to check focus with one click, if you set it up right. It has a spot meter too but to check the histogram on spot area results, you'll need to load the image into a laptop & make a selection on the area of interest. The metering systems on modern DSLRs are too clever, making all sorts of assumptions, not like a manual meter. I have no idea how this translates to film exposure but I suspect the simplest digital histogram would be about as useful as the most advanced for translating to film exposure. Simply looking at the LCD image is sort of useless given the variation in visibility & contrast in different lighting conditions so for exposure, zooming doesn't help without a laptop. Some digital's allow cropping the image in-camera where you could then see the cropped histogram but that's an awful lot of bother. This is a major drawback of EVF cameras with which it can be difficult to even achieve critical manual focus on a tripod. Film, negative in particular, has more latitude than digital. Hence I That isn't true for current DSLRs. Agreed. suspect the results of a digital histogram will not be worth the waste of battery power as the results will not translate into information captured on film. That might be the case. On the other hand if the photographer understands the technology it can be of significant value. I'm not sure the significance equals the price of a good DSLR for a person who wants to shoot film though... But certainly one instance would be for medium or large format film users. A DSLR would stomp all over using a Polaroid. Any digital with reasonable manual control would be super-useful tethered to a laptop as a mega-polaroid. The LCD displays are not bad (newer ones are much better) but are a far cry from a polaroid or a laptop. -- Paul Furman Photography http://edgehill.net Bay Natives Nursery http://www.baynatives.com |
#17
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digital camera as exposure meter
viewerofrecphoto wrote:
looking for a digital camera to use as an exposure meter and histogram display for my film camera. preferred features: - small size - low price - accurate histogram - iso range 100-1600 - zoom range 24-200 (35mm equiv) - manual aperture & shutter speed - ease of use to look at histograms resolution/noise are not important. But a good (£300) meter is a lot cheaper than a digital camera and 24-200 lens. Another thing: many digital sensors do not respond exactly as a film would at the named ISO rating. Canon, in particular, seem to claim a quite different ISO to the actual response. The built-in meters compensate but this will not help you metering for film. The histogram is of almost no use whatsoever with respect to film, at least unless you recalibrate it for your film. What have you got against buying a decent meter? Just out of interest why do you need a zoom meter? Take multi-spot readings of the bits you're interested in and the meter will average them. Or alternatively, something you can't do with a camera is incident light metering, measuring the light falling on a subject rather than that reflected. Just one other thought, if you still find a £300 meter too expensive, you can spend half that on a Canon T90 and lens which is one of the finest meters ever made. Hell, you can even get one with a stuck shutter for peanuts as you don't want to take photos with it. Rich |
#18
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digital camera as exposure meter
Paul Furman wrote:
Floyd L. Davidson wrote: "gowanoh" wrote: Ditto for the LCD screens built into dSLRs as they cannot resolve enough detail and brightness levels to tell you anything of value. Because of their small size the screens are often misleading about whether you even had proper focus for the shot. With a good DSLR the LCD image can be magnified several times, allowing analysis of focus. (That is cumbersome, and I have never bothered to actually do it, but for photographing static scenes it should work just fine.) The D200 is easy to zoom in to more than 100% magnification to check focus with one click, if you set it up right. It isn't something I have an interest in, but I'm sure that for those who need to know if the last image was or was not in focus it certainly is easy enough to do. In my case, 99% of the time it is of no significance because the scene can never be recreated, so what I got already is all I'll get. It has a spot meter too but to check the histogram on spot area results, you'll need to load the image into a laptop & make a selection on the area of interest. Off hand I can't think of a circumstance where a histogram, or any type of spectoral analysis, of the area metered would be of any value. The metering systems on modern DSLRs are too clever, making all sorts of assumptions, not like a manual meter. Very true for "matrix metering" and that sort of thing. But spot metering doesn't do that cute stuff. However your point is well taken in that for the purposes we were discussing it would be very wise to carefully understand which metering modes are making unknown assumptions and which are not, and avoid the ones where it isn't possible to know which assumptions are being used (things like matrix metering where there is a table of 40,000 different combinations stored in the firmware!). I have no idea how this translates to film exposure but I suspect the simplest digital histogram would be about as useful as the most advanced for translating to film exposure. Simply looking at the LCD image is sort of useless given the variation in visibility & contrast in different lighting conditions so for exposure, zooming doesn't help without a laptop. It would indeed help, but it has to be done right. Here's an example of what I'm thinking of: If the entire scene is framed in the DSLR viewfinder (with ISO and exposure compensation settings that match the lenses and film being used by the other camera), the "correct" exposure can be determined very precisely by making a few exposures and observing the blink on over exposure display. Once exposure is set at 1/3 of an fstop below an exposure that causes any desired highlight to blink, the fstop and shutter speed are noted. It is perhaps interesting to take a "whole screen" exposure reading to see what the average reflectance of the entire scene is by comparison, but frankly that is not really important. What is important is to zoom in on a shadow area that has detail of interest, and use a spot meter to measure that area. One has to know the dynamic range of the film/processing system being used, and imperical knowledge is the only way that a useful comparison can be made. If we know, for example, that a we can get detail in shadows that are 5 fstops below a "correct exposure", then the difference between the correct exposure determined by blinking highlights and the shadows determined by spot metering tells us *exactly* how much detail is going to be recorded in the shadow area measured. In that case, with a 5 fstop range if it measured 6 fstops down *no* detail is going to be recorded, while if it measured at 4 fstops then a significant amount of detail will be there, but there certainly won't be any headroom! (Keep in mind that the spot meter is telling us what exposure would be necessary to get that area to record as an average 18% grey. Recording 5 fstops below 18% grey is a lot of dynamic range...) Some digital's allow cropping the image in-camera where you could then see the cropped histogram but that's an awful lot of bother. This is a major drawback of EVF cameras with which it can be difficult to even achieve critical manual focus on a tripod. Film, negative in particular, has more latitude than digital. Hence I That isn't true for current DSLRs. Agreed. A persistent myth... :-) suspect the results of a digital histogram will not be worth the waste of battery power as the results will not translate into information captured on film. That might be the case. On the other hand if the photographer understands the technology it can be of significant value. I'm not sure the significance equals the price of a good DSLR for a person who wants to shoot film though... But certainly one instance would be for medium or large format film users. A DSLR would stomp all over using a Polaroid. Any digital with reasonable manual control would be super-useful tethered to a laptop as a mega-polaroid. The LCD displays are not bad (newer ones are much better) but are a far cry from a polaroid or a laptop. I don't agree that the LCD is a far cry from a Polaroid, but I do agree that tethering to a laptop adds at least an order of magnitude _more_ functionality. Of course that works better in a studio than it does in a swamp... (I spend more time in swamps.) -- Floyd L. Davidson http://www.apaflo.com/floyd_davidson Ukpeagvik (Barrow, Alaska) |
#19
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digital camera as exposure meter
Richard Polhill wrote:
viewerofrecphoto wrote: looking for a digital camera to use as an exposure meter and histogram display for my film camera. preferred features: - small size - low price - accurate histogram - iso range 100-1600 - zoom range 24-200 (35mm equiv) - manual aperture & shutter speed - ease of use to look at histograms resolution/noise are not important. But a good (£300) meter is a lot cheaper than a digital camera and 24-200 lens. A $600 camera (Nikon D40 with an 18-55mm kit lense) will run circles around any $600 light meter. At $800 for a DSLR the OP might nearly want to simply ditch shooting with film at all, and use only the "meter"! Another thing: many digital sensors do not respond exactly as a film would at the named ISO rating. Canon, in particular, seem to claim a quite different ISO to the actual response. The built-in meters compensate but this will not help you metering for film. As with *any* meter, one would need to "calibrate" to match the camera/film/lenses being used. The histogram is of almost no use whatsoever with respect to film, at least unless you recalibrate it for your film. What have you got against buying a decent meter? Just out of interest why do you need a zoom meter? Take multi-spot readings of the bits you're interested in and the meter will average them. Or alternatively, something you can't do with a camera is incident light metering, measuring the light falling on a subject rather than that reflected. The camera and film will be responding to the reflected light though, not to incident light. The usual problem with use of a reflected light meter is the averaging of an entire scene. The accuracy of the reading depends on the *photographer's* (not the meter) ability to judge if the scene is actualy 18% reflectance, and how much brighter the highlights are than the average. Some photographers do that quite well, most don't. Use of an incident light meter eliminates the need to adjust the average in relation to 18% reflectance, but there is still the problem of relating the highlights to the average. But if one actually uses a "spot" meter to determine the an appropriate exposure level for the highlights, and then confirms that the shadows are within the dynamic range of the film (or the electronic sensor with a digital camera), a "reflected meter" reading is by far more acurrate. Obviously a zoom meter is quite useful for that task. Just one other thought, if you still find a £300 meter too expensive, you can spend half that on a Canon T90 and lens which is one of the finest meters ever made. Hell, you can even get one with a stuck shutter for peanuts as you don't want to take photos with it. That might well be just about as useful as a $600 meter. But just like a light meter, it pales by comparison to a DSLR. -- Floyd L. Davidson http://www.apaflo.com/floyd_davidson Ukpeagvik (Barrow, Alaska) |
#20
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digital camera as exposure meter
Floyd L. Davidson wrote:
Richard Polhill wrote: viewerofrecphoto wrote: looking for a digital camera to use as an exposure meter and histogram display for my film camera. preferred features: - small size - low price - accurate histogram - iso range 100-1600 - zoom range 24-200 (35mm equiv) - manual aperture & shutter speed - ease of use to look at histograms resolution/noise are not important. But a good (£300) meter is a lot cheaper than a digital camera and 24-200 lens. A $600 camera (Nikon D40 with an 18-55mm kit lense) will run circles around any $600 light meter. At $800 for a DSLR the OP might nearly want to simply ditch shooting with film at all, and use only the "meter"! Thereby solving all his problems, bring world peace, banish poverty, hunger and suffering. Of course. How exactly will it "run rings around" a meter? It IS a meter. And just what the **** is a "lense"? Another thing: many digital sensors do not respond exactly as a film would at the named ISO rating. Canon, in particular, seem to claim a quite different ISO to the actual response. The built-in meters compensate but this will not help you metering for film. As with *any* meter, one would need to "calibrate" to match the camera/film/lenses being used. Sure right. Perhaps with a DSLR... The histogram is of almost no use whatsoever with respect to film, at least unless you recalibrate it for your film. What have you got against buying a decent meter? Just out of interest why do you need a zoom meter? Take multi-spot readings of the bits you're interested in and the meter will average them. Or alternatively, something you can't do with a camera is incident light metering, measuring the light falling on a subject rather than that reflected. The camera and film will be responding to the reflected light though, not to incident light. The usual problem with use of a reflected light meter is the averaging of an entire scene. The accuracy of the reading depends on the *photographer's* (not the meter) ability to judge if the scene is actualy 18% reflectance, and how much brighter the highlights are than the average. Some photographers do that quite well, most don't. Use of an incident light meter eliminates the need to adjust the average in relation to 18% reflectance, but there is still the problem of relating the highlights to the average. It doesn't occur to you that there will often be elements in a view that are outside the exposure latitude of the chosen medium, then? You can only expose correctly for the bit you want. But if one actually uses a "spot" meter to determine the an appropriate exposure level for the highlights, and then confirms that the shadows are within the dynamic range of the film (or the electronic sensor with a digital camera), a "reflected meter" reading is by far more acurrate. ********. Sorry, that's total, unmitigated bull****. Unless you mean something different by the word "acurrate" than what I assumed: "accurate". Obviously a zoom meter is quite useful for that task. Zoom? Why? Just one other thought, if you still find a £300 meter too expensive, you can spend half that on a Canon T90 and lens which is one of the finest meters ever made. Hell, you can even get one with a stuck shutter for peanuts as you don't want to take photos with it. That might well be just about as useful as a $600 meter. But just like a light meter, it pales by comparison to a DSLR. What? And how does a spot meter in one camera get blown away by the spot meter in another? I guarantee the T90 meter is as accurate as any DSLR, so what else do you think the guy will gain? Oh yeah: world peace, etc... |
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