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Topic: Exposure times

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	GNIRS Exposure times
		For faint targets in low background situations (J, H, high-resolution K), the maximum exposure time is determined by sky variability and radiation events with the short cameras.
		In this case, we recommend a maximum exposure time of 15 minutes and dithering (either along the slit or off the slit) to facilitate sky subtraction and cosmic ray (and radiation event) corrections.
		In the thermal infrared, the maximum exposure time is always set by the background (even with the deeper well) and depends on the wavelength and the instrument configuration.
	www.gemini.edu /sciops/instruments/nirs/nirsExposures.html (578 words)

	Intercomparison of exposure times of a dosimeter system for evaluation of the ultraviolet spectrum in different ...
		The exposure times for the spectrum evaluator are a compromise between a sufficient UV exposure to produce a measurable change in optical absorbance of the material, but not long enough to either saturate the most sensitive dosimeter material or allow an unacceptable large change in the source spectrum.
		For the different environments, the exposure times required for the spectrum evaluator were found to be a compromise between producing a measurable change in optical absorbance of the dosimeter material and reducing the saturation of the dosimeter material and minimising any changes in the source spectrum.
		The exposure times ranged from 5 minutes to 3 hours and were dependent on the UV irradiances and the general shape of the UV spectrum, which was influenced by the UV environment.
	www.photobiology.com /UVR98/parisi2 (1917 words)

	Olympus Microscopy Resource Center: Photomicrography - Fundamentals of Film Exposure
		Exposure varies directly as the square of the magnification and inversely as the square of the numerical aperture.
		After exposure parameters have been determined under a set of controlled conditions using white light from the microscope lamp (no filters present), a new set of parameters must be introduced to compensate exposure times when a filter is added.
		Exposures should be conducted in a geometrical progression (for example exposures of 1, 2, 4, 8, 16, 32 seconds and so on) using a constant voltage setting on the microscope lamp.
	www.olympusmicro.com /primer/photomicrography/filmexposure.html (6040 words)

	Determining Exposure Times for Pinhole Cameras [pinhole.cz]
		Determining the correct exposure time for a pinhole camera is truly a hard nut to crack.
		However, if we want to minimise the risk of poor-quality photographs, it would be helpful to be able to calculate exposure times as simply as possible so that one has more time to concentrate on the photograph itself and also so the whole process does not become a mathematical nightmare.
		For long exposure times, usually for exposures longer than several seconds, it is necessary to extend the measured time.
	www.pinhole.cz /en/pinholecameras/exposure_01.html (942 words)

	Moon Photography - A How To Guide
		When you bracket your exposure, it simply means that you make an photograph at the setting you think is correct, but you also photograph the same subject several more times, making slight changes in either the shutter speed setting or aperture.
		The exposure time is calculated by determining the focal length (F) and the f/ratio of the telescope system.
		Always bracket exposures since exposure times given by formulas are approximate, varying according to the exact phase of the Moon, atmospheric conditions, etc. To be safe, bracket at one and preferably two stops on both sides of the exposure suggested by the formula.
	home.hiwaay.net /~krcool/Astro/moon/howtophoto (1452 words)

	Method of determining exposure times for photographic copying material - Patent 4104069
		These isodensity lines are graphically determined and constitute a basis for the subsequent determination of the relationship between the two exposures in the two different colors and the total exposure time, for copying a particular original exhibiting a range of densities which has been determined previously.
		Upon elapse of a yellow exposure time T.sub.G sufficient to produce a medium copy density in the case of a medium original density, the light source 1 is extinguished, or alternatively the aforementioned shutter is closed.
		In this case, equation (4), used to determine the individual exposure components, the factors b and g, is modified as follows: ##EQU4## In this case, it is assumed that the Schwarzschild exponents p for the two color exposures are equal, and that they vary similarly to each other with variations in copy density.
	www.freepatentsonline.com /4104069.html (2677 words)

	Calculating Exposure Times (Site not responding. Last check: 2007-10-08)
		Calculating the exposure time for an object depends on the object's: brightness (magnitude), seeing, sky transparency, sky brightness, moon phase, telescope+instrument+detector sensitivity, wavelength (filter) and the desired signal to noise ("contrast").
		A good, though technical, guide to calculating exposure time is found in the NOAO Direct Imaging Manual for Kitt Peak, written by P. Massey et al.
		Just scale the exposure times accordingly, rememebering that a difference of 1 mag is a factor of 2 in brightness, and that a difference of 5 mag is a factor of 100.
	hou.lbl.gov /exptime.html (162 words)

	NICMOS Camera 2 ACQ Exposure Times (Site not responding. Last check: 2007-10-08)
		The ACQ exposure times (keyword exptime) in the science headers are incorrect.
		The ACQ exposure times as specified by the PI in the Phase II are being executed.
		If there are large differences in exposure time between the corrected value and the requested exposure in the Phase II template, check to make sure the requested time is a legal quantized exposure time.
	www.stsci.edu:8082 /hst/nicmos/calibration/advisories/acqexptime_25August98?printable=1 (260 words)

	Starizona CCD Guide - Exposure Tips (Site not responding. Last check: 2007-10-08)
		For planetary imaging, the right exposure time can be more critical as there is a balance between short exposures to avoid atmospheric turbulence and longer exposures to get the most image data possible.
		If your CCD camera is unguided, the exposure times will be determined by the accuracy of the mount's drive and the focal length of the telescope.
		If you know the exposure time used to take an image you like, you can fairly easily figure how long an exposure is required with your equipment to achieve a similar result.
	www.starizona.com /ccd/tipsexposure.htm (780 words)

	Computing Exposure Times
		In the meantime, accurate information for estimating exposure times can be found on the OSU Andicam Page.
		Information for estimating exposure times for CT-1.3m telescope can be found on the OSU Andicam Page.
		Please use the CTIO Infrared Imager Exposure Time Calculator for CT-4m observations with ISPI.
	www.noao.edu /gateway/ccdtime (495 words)

	Reciprocity Failure (Site not responding. Last check: 2007-10-08)
		The exposure of a film is based on the intensity of light falling on the emulsion multiplied by the exposure time.
		Exposures outside of this time range need to be compensated for.
		For adjusted times between 10 seconds and 100 seconds you should reduce development time by around 20% and for adjusted times of 100 or more, development time should be reduced around 30%.
	home.pacbell.net /mkirwan/reciprocity_failure.htm (259 words)

	Options - Exposure (Site not responding. Last check: 2007-10-08)
		As darker images are displayed, longer exposure times are used and when lighter images are displayed, shorter exposure times are used.
		All exposure times are expressed in milliseconds (for example, 500 indicates an exposure time of 1/2 second).
		Note that the entered exposure time will be used regardless of whether that length of time helps to maximize accuracy.
	www.milori.com /help/options_exposure.htm (215 words)

	BUG: Exposure times are incorrect (Site not responding. Last check: 2007-10-08)
		The exposure times in all GRIM II exposures taken after 30 October 1994(1) are longer than requested.
		The indications are that the actual exposure time is equal to the FITS header parameter "OPENTIME" + 1.09 sec.
		This timer is used as the exposure timer.
	astro.uchicago.edu /home/web/nir/GRIM_II/Bugs/expTim.html (141 words)

	ND and Exposure time Effects for SXT (Site not responding. Last check: 2007-10-08)
		The dark blue ones are the shortest exposures, no-ND filter and MBE level 0, and exposure time of about 0.95 msec, the lighter blue ones are ND-fliter images with MBE=2, and exposure times of 1.4 msec.
		A couple of things should be noted; 1) the 2.9 msec exposures are slightly higher than the 3.1 msec ND exposures; this can be attributed to the ND filter, and 2) the 0.95 msec exposures are lower than the rest; this is an effect of the shorter exposure time.
		It is unlikely that this is an effect of time variation in the actual dark current; if dark current varied much with exposure time, we would expect it to vary with the exposure time before the correction for the ND filter.
	hessi.ssl.berkeley.edu /~jimm/nd_demo.html (1916 words)

	Exposure strategies for digital cameras with manual exposure controls (Site not responding. Last check: 2007-10-08)
		Because of the way the exposure duration is actually controlled inside film cameras, the term shutter speed is often substituted for exposure time, but to call for an exposure of 1/250 sec is clearly to specify a duration, not a speed.
		In the Additive Photographic Exposure System EV table below, exposure value (EV) is defined as the sum of the respective stop numbers corresponding to the aperture and exposure time of interest, with one unit of EV corresponding to one stop of exposure.
		Often, this is all the control you need to get the shot in your mind's eye, but higher-end digital cameras with exposure compensation and fully manual exposure allow you break the bonds of camera-imposed exposures to reach the tonality and motion control you had in mind.
	dpfwiw.com /exposure.htm (13516 words)

	Reciprocity Failure Correction
		However, there are times when photographers find the need to use exposure times that lie outside of the range where their film of choice gives good reciprocity results.
		In this range of exposure times, selecting a smaller lens aperture in order to increase depth of field, or to choose the aperture of maximum sharpness for a given lens, leads to an underexposure of the image on the film if the reciprocity law is assumed to hold.
		Most of the time, the recommended corrections are in terms of increased lens aperture, though some manufacturers give a correction factor that can be multiplied to the indicated exposure time (the time a light meter would give you) to yield a corrected exposure time.
	home.earthlink.net /~kitathome/LunarLight/moonlight_gallery/technique/reciprocity.htm (4138 words)

	mkaz.com : Exposures for Moonlight Photography
		The exposure times are rough starting points, the subject surface (reflection), ambient light and other factors will effect your exposure.
		So I used the base exposure for ISO 100 film at f/8 as 8 minutes, since 30 seconds of 8 mins is only a difference of 6% which is a small difference overall.
		The characteristics of film is that during an exposure it is initially very sensitive to light but as exposure time increases the film's ability to record light is diminished.
	www.mkaz.com /photo/tools/moonlight.html (632 words)

	Bulb / Lamp Types And Exposure Times -- Agifnat.org \| Tanning Beds \| Commercial Tanning Beds \| Home Tanning Beds \| ... (Site not responding. Last check: 2007-10-08)
		Your exposure time will depend on a number of factors, including the bulb or lamp type and strength, your desired level of tanning, your susceptibility to tanning, and your own skin.
		These exposure and development times should be taken into account when planning for a tanned look for a night out or a special occasion – advanced preparation is essential.
		For those that have not used tanning beds before, the initial exposure may be for a very short time, which can mean a matter of five minutes or so.
	www.agifnat.org /bulb-lamp-types-and-exposure-times.html (564 words)

	Grism ETC (Site not responding. Last check: 2007-10-08)
		The STSCI NICMOS ETC exposure times is using However, it can be used to estimate the background count rate and noise of grism exposures.
		The most difficult part in estimating exposure times is to predict the background and its noise in the image, which varies substantially from image to image.
		For an one hour exposure time, the background noise n_back in DN (including a single readout) can be taken from the table above.
	ecf.hq.eso.org /instruments/nicmos/exposure_time.html (357 words)

	Reciprocity and Special Filter Data for KODAK Films: Tech Pub E-31 (Site not responding. Last check: 2007-10-08)
		This means, for example, that an exposure of f/16 at 1/60 second is equivalent to an exposure of f/11 at 1/125 second.
		However, all photographic emulsions are subject to an effect often called "reciprocity-law failure." At exposure times outside the above range, you will begin to see underexposure (loss of effective film speed) at the normally calculated exposure setting, a change in contrast, a color shift, or a combination of these effects.
		It may be difficult to use the previous table to estimate the adjusted exposure times for indicated times between 1and 100seconds.
	www.kodak.com /global/en/professional/support/techPubs/e31/e31.jhtml (1134 words)

	Astrophotography Exposure Table
		This is a table for determining the approximate exposure times for deep space astronomical objects depending on the f/ratio of the optical system used.
		The table is based on experience of exposure times from a semi-dark site that result in near maximum acceptable sky fog.
		Look up the f/ratio you will use in the left column and read off the exposure time in the columns to the right, depending on the elevation of the object and whether or not a filter will be used.
	www.astrocruise.com /astroexp.htm (379 words)

	Short Ultrasound Exposure Times for Noninvasive Insulin Delivery in Rats Using the Lightweight Cymbal Array (Site not responding. Last check: 2007-10-08)
		The last group used insulin with ultrasound operating with a 5-minute exposure to examine the effects of using short ultrasound exposure times on delivery.
		For the 10- and 5-minute ultrasound exposure groups, the glucose level was found to decrease from the baseline to -174.6 ± 67.2 and -200.4 ± 43.4 mg/dl measured after 1 hour, respectively.
		These results indicated that ultrasound exposure times do not need to be long to deliver a clinically significant insulin dose to reduce a high blood glucose level.
	www.ieee-uffc.org /archive/uffc/trans/Toc/abs/04/t0420176.htm (352 words)

	3.1.3.6 `Smear' Exposure Times
		So for a full frame exposure 3.3 seconds of integration time occurs while the target is stationary, and 41 milliseconds occurs with the target image smeared over 1024 vertical rows of pixels with the width of the point spread function of the telescope.
		For a point source the integration time per CCD frame within a PSF sized region is equal to the dwell time (for a full frame this is 3.3 seconds).
		The repetition rate of frames includes the smear time (for a full frame this is 3.34 seconds).
	www.astro.psu.edu /xray/docs/sop/node63.html (313 words)

	Determination of the Effective Exposure Times
		The effective exposure times for the 1983-1985 Epoch ITFs were derived by Imhoff (1984b and 1986), by De La Peña and Coulter (1996) for the 1992 Epoch LWP ITF, and by De La Peña for the LWR ITFs.
		During the creation of the 1983-1985 ITFs in their own geometric space for the NEWSIPS system, if additional images were deemed usable in contrast to those originally chosen by Imhoff, the effective exposure times were modified to reflect the use of additional images.
		These exposure values have been normalized to an arbitrary scale such that the FN associated with the lowest level of an ITF is 0.0.
	www.star.bris.ac.uk /~mbt/iuedr/newsips/node51.html (126 words)

	Canon Digital Photography Forums - Infrared Film Exposure Times
		I'm trying to figure out what kind of exposure times I should be using with Kodak High Speed IR film and a Hoya R72 filter.
		The spec sheet with the film gives some sample exposure times (ie: 1/60 at f/8 for nearby sunlit scenes), but it says that is when using a Kodak Wratten gel filter no. 25.
		Exposure is a "hit or miss" kind of thing because the amount of infrared light varies greatly from day to day, even from hour to hour.
	photography-on-the.net /forum/printthread.php?t=53559 (713 words)

	Exposure Times for Deep Sky Astrophotos
		The times will have to be adjusted for varying equipment and conditions, but this should get you started.
		Different films also require different exposure times, but not necessarily in relation to their "speeds".
		This exposure time will allow you to capture the faintest detail possible without picking up too much sky glow (artificial or natural).
	www.darkskyimages.com /gexpose.htm (348 words)

	Determining the Correct Ratio of Exposure Times to Use for Color Imaging (R,V,B) (Site not responding. Last check: 2007-10-08)
		If, for example, the average pixel value (minus 100) in the V image is half that in the R image, and the average pixel value (minus 100) in the B image is one-fourth that in the R image, then the correct ratio of image exposures would be 1:2:4 for the R, V, and B filters.
		Again, you should be able to determine the ratios of exposure times as with the illuminated screen.
		The advantages of many shorter exposures: (1) if you do something wrong during an exposure you lose 5 minutes, not 40 and (2) if you median combine the set of images cosmic ray defects are automatically removed, while many such defects will accumulate in one long image.
	www.phys.vt.edu /~jhs/phys3154/color.html (614 words)

	SomethingLeet - exposure times? (Site not responding. Last check: 2007-10-08)
		If using fiml they most likely used this "remote" device (i forget the friggn name of it) that screws into the shutter release so that you can activate and scew it in and leave it be.
		so basically the "bulb" function gives you unlimited shutter time, and they most likely used that lil guy i was talking about and left their camera idle for 30 min.
		the sad thing is, very long exposures aren't that great for digital cameras, leaving the camera on for such a long time will cause the camera to overheat, amplifying the noise and causing hot spots to appear.
	www.somethingleet.com /forum/showthread.php?threadid=28666 (805 words)

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