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Sigma SD14 ISO 50
- Thread starter xpatUSA
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absquatulate
Guest
DP2's have (Not Merrills) the same ability, it's ISO 100 +1 exp compensation, the same as Canon offer on the 5D series.
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Do you have any examples of ISO 50 colors not looking right Scott?
furtle
Senior Member
LOL . .
With less headroom - more or less none actually - perhaps more of the scene will be in the non-linear region of the sensor with perhaps one or even two channels non-linear. That would mess up the conversion to XYZ and therefore the resulting RGB values.
Assuming the SD14 conforms to CIPA DC-004, then an AE exposure at 100 ISO with no EC should result in an average of 18% saturation of the sensor. With the SD14 being ISO-less (no AFE), that gives a headroom of 82% before saturation. At 50 ISO, the metering will set 36% saturation of the sensor, leaving only 64% to go. The less headroom for the same scene, the higher the probability of wrong colors.
By "headroom" here, I am talking about simple sensor exposure with simple basic metering and none of the confusing talk about expecting scene highlights to have 100% reflectance, etc, as found in the ISO Standard :-(
We know from meta-data that Foveon specifies the sensor to be saturated at around 6000 raw value. But from RawDigger we also know that we can raw values of 7000+ from a scene with specular highlights suggesting non-linearity over 6000 and the possibility of incorrect colors.
P.S. Assuming that a saturated sensor results in exactly 255 in sRGB on your screen, then 36% gets you about 160 gray value.
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"What we've got hyah is Failyah to Communicate": 'Cool Hand Luke' 1967.
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rick decker
Forum Pro
Hi Ted:
I ran some comparisons several years ago. Seems that there is less noise in the shadows.
Rick
I ran some comparisons several years ago. Seems that there is less noise in the shadows.
Rick
L
Lin Evans
Guest
Thanks Lin,
My main reason for posting was bring the availability of ISO 50 on the SD14 to the notice anybody who had only read the manual and had not set the ISO to "extended" and therefore might not have known about it.
How excellent to see actual color checker images which should certainly address Scottelly's concerns expressed earlier in this thread.
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"What we've got hyah is Failyah to Communicate": 'Cool Hand Luke' 1967.
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SigmaChrome
Forum Pro
I shot lots of ISO 50 on the SD14. Once you understand how to manage the highlights, the results are simply stunning. Richer, finer grain; much like Kodachrome 64 and 25.
Examples here and below.
--
Regards,
Vitée
Capture all the light and colour!
Examples here and below.
--
Regards,
Vitée
Capture all the light and colour!
Galleries by Vitee
www.pbase.com
Inspired by Lin's shots, I couldn't resist some target shooting of my own . .
TIFF outputs from SPP:
Color-picked just below the Card and brightness equalized
In spite of the correct difference in camera settings (1 EV), the 50 ISO TIFF exported as 0.3 EV lighter. In terms of color, the hues are about the same but the patches in the 50 ISO TIFF are slightly more saturated, many of them 100% (thanks, SPP 3.5.2, for the really enthusiastic SD14 conversion).
Raw histograms:
Noticeable is the greater number of "missing levels" in the 100 ISO shot - and of course the 1 EV greater exposure for 50 ISO and a significantly different shape for the shadows.
Here's good old SPP's "zero" sharpening:
A slightly higher overshot at 50 ISO (left).
And the all-important MTF:
Here we see the gross effects of SPP's over-sharpening in all their glory. If you like artifacts in your SD14 shots, do leave that slider at zero. :-D
Again at left, 50 ISO "wins" with a bigger hump above 100% and an outrageous MTF at Nyquist.
--
"What we've got hyah is Failyah to Communicate": 'Cool Hand Luke' 1967.
TIFF outputs from SPP:
Color-picked just below the Card and brightness equalized
In spite of the correct difference in camera settings (1 EV), the 50 ISO TIFF exported as 0.3 EV lighter. In terms of color, the hues are about the same but the patches in the 50 ISO TIFF are slightly more saturated, many of them 100% (thanks, SPP 3.5.2, for the really enthusiastic SD14 conversion).
Raw histograms:
Noticeable is the greater number of "missing levels" in the 100 ISO shot - and of course the 1 EV greater exposure for 50 ISO and a significantly different shape for the shadows.
Here's good old SPP's "zero" sharpening:
A slightly higher overshot at 50 ISO (left).
And the all-important MTF:
Here we see the gross effects of SPP's over-sharpening in all their glory. If you like artifacts in your SD14 shots, do leave that slider at zero. :-D
Again at left, 50 ISO "wins" with a bigger hump above 100% and an outrageous MTF at Nyquist.
--
"What we've got hyah is Failyah to Communicate": 'Cool Hand Luke' 1967.
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These shots are all well and good but I don't see any amazing differences in my test images other than the obvious -1 EV difference in sensor exposure of 100 ISO compared to 50.I shot lots of ISO 50 on the SD14. Once you understand how to manage the highlights, the results are simply stunning. Richer, finer grain; much like Kodachrome 64 and 25.
Examples here and below.
--
Regards,
Vitée
More to the point: Is there really any difference at all between an image shot at 50 ISO, 0 EC and one shot at 100 ISO and +1 EC? Assuming, of course ,that no sensor channels are blown or bottomed in either case.
Shooting at 100 ISO and +1 EC does not necessarily mean that any channels will blow. For example, in a scene with predominant highlights, the standard advice is to apply positive EC to avoid under-exposure of some shaded subject (the classic black cat on snow). The metering will try to render the scene average as mid-gray (about 13% on the sensor) and the poor cat could come out as a black blob buried in noise. Applying even +2 EC would expose that snow at about 52% on the sensor, about 189/255 in sRGB.
Since SPP applies a multiplier to account for the ISO setting (non-AFE cameras), a proper image comparison would involve equalizing the histograms in SPP before saving for comparison of image quality.
My bet is that the difference in IQ would be insignificant, with the claimed superior IQ at 50 ISO being due to the greater probability that a 50 ISO shot is more properly "Exposed-To-The-Right".
--
"What we've got hyah is Failyah to Communicate": 'Cool Hand Luke' 1967.
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SigmaChrome
Forum Pro
The difference may not be "amazing" but it is significant and quite obvious - and that's all that matters to me.
When Sigma offered the firmware update offering ISO 50 and I applied it to my camera, the resulting shots were a pleasant surprise.
Following Sigma's Notes regarding using ISO 50 on the SD14 made good sense and produced excellent results, like these.
Regardless of your betting skills, most of us SD14 users here on DPR were very happy with the 50 ISO results.
--
Regards,
Vitée
Capture all the light and colour!
http://www.pbase.com/vitee/image/98008547/small.jpg
http://www.pbase.com/vitee/galleries
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OK. I fold.
[edit] What an amazing difference there must be between the SD14 and the SD1 Merrill !! A user of both gets his best results from the SD14 at ISO 50 and yet gets his best results from the SD1M at ISO 200. Quite remarkable . . [/edit]
--
"What we've got hyah is Failyah to Communicate": 'Cool Hand Luke' 1967.
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