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07/25/2008 07:43:44 AM · #1 |
I know the question may sound odd and truthfully I have never thought about it.
Based on the knowledge that some lens that has a max f# of f/2.8 or larger sometimes has has a sweet spot [better detail] when set at f/4.0 could ISO also have a sweet spot.
I usually shoot everything at ISO-100 but shot this picture at ISO-400 because I was in the sun but the subject was in the shade on an overcast day. Buy bumping up the ISO to 400 it allowed me to get a faster shutter [1/60th]. While processing the image using the same basic work flow I noticed the details and overall sharpness of the photo seemed to be far better than ISO-100.
So my question is: When setting the ISO even though ISO-100 would be sufficient is it possible that a higher ISO such as 400 would produce a photograph with better detail and clarity?
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07/25/2008 08:05:16 AM · #2 |
Interesting question, and that is one sharp squirrel! I've been shooting more often with ISO 200 and 400, mostly out of necessity, and haven't been dissppointed with the results. Maybe the 40D has a sweet spot? Watching this thread for any bits of wisdom.
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07/25/2008 08:12:07 AM · #3 |
I would agree the colour & sharpen effect you cite can be observed in some files. The effect sometimes is startling.
I have attributed the effect to the introduction of more grain from higher iso, however w/your camera I would think @ iso 400, it would be negligible.
Can you imagine the next generation of photoshop plugins which include legacy digital camera noise as grain option along side Tri-X in the drop down -
Message edited by author 2008-07-25 08:15:11. |
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07/25/2008 08:13:15 AM · #4 |
Originally posted by SDW:
I know the question may sound odd and truthfully I have never thought about it.
Based on the knowledge that some lens that has a max f# of f/2.8 or larger sometimes has has a sweet spot [better detail] when set at f/4.0 could ISO also have a sweet spot.
I usually shoot everything at ISO-100 but shot this picture at ISO-400 because I was in the sun but the subject was in the shade on an overcast day. Buy bumping up the ISO to 400 it allowed me to get a faster shutter [1/60th]. While processing the image using the same basic work flow I noticed the details and overall sharpness of the photo seemed to be far better than ISO-100.
So my question is: When setting the ISO even though ISO-100 would be sufficient is it possible that a higher ISO such as 400 would produce a photograph with better detail and clarity?
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No. The lower the ISO, the less noise (and artefacts when shooting in JPG) and the sharper the image. I shoot at ISO 50 when I can. |
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07/25/2008 08:15:37 AM · #5 |
Originally posted by SDW:
While processing the image using the same basic work flow I noticed the details and overall sharpness of the photo seemed to be far better than ISO-100.
So my question is: When setting the ISO even though ISO-100 would be sufficient is it possible that a higher ISO such as 400 would produce a photograph with better detail and clarity?
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Don't think so. To really see the difference between the two ISO speeds you need to photograph the subjects at the same time of day with optimal lighting conditions that let you expose correctly and precisely. Then you can compare to see the difference but i'm willing to bet the lower ISO speed will win. Unless your 40D has something that every other camera doesn't.
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07/25/2008 08:47:07 AM · #6 |
With my SLR, I normally use 400 as my default ISO setting. On an SLR the noise is negligible, and it allows me a faster shutter speed. A benefit, since I don't have a stabilized lens. I got similar results with a similar subject:
Actually, it looks like this was shot at an ISO of 800, which I used so I could have a narrower aperture.
Message edited by author 2008-07-25 08:49:12. |
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07/25/2008 08:48:04 AM · #7 |
Originally posted by Jac:
..... Unless your 40D has something that every other camera doesn't. |
Mine has a death-ray!
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07/25/2008 08:51:04 AM · #8 |
I had read where there is a "base" ISO for the sensor in most DSLR's that could be considered the "sweet spot" I suppose. Can't find the article now...think it may have been something I read in Popular Photography magazine FWIW.
Doing a bit of quick searching brought me to this short, but interesting article at digitalphotopro.com ==> Digital ISO Speeds
A key (for me anyway) excerpt from the article is this: "A digital image sensor has a native ISO. When you adjust the ISO setting, the sensor itself isn̢۪t changing; rather, the amplification is changing. This is fundamentally different from film."
There's some pretty scientific info out there, check ISO at wikipedia.com, that's not discerable to me no matter how many cups of coffee I chase down this morning. :-) |
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07/25/2008 08:57:39 AM · #9 |
I always shoot with my iso set at 100, just like the way my images come out.
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07/25/2008 09:35:15 AM · #10 |
I prefer 100 ISO and I can usually tell, in my images at least, at what ISO the image was taken. Additionally, if I know the ISO, I can tell with which camera (rebel or 30D)the image was taken. For me, it is the exposure that plays the biggest part; if the image as a whole is under exposed by 1 or 2 stops (due to spot metering), a 100 ISO shot can look like crap if the exposure is 'corrected.' (I tend to like underexposed images over 'correctly' exposed ones.)
So, a camera can take 400 ISO shots that look better than 100 ISO shots depending on the accuracy of the exposure. IMO. I think. |
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07/25/2008 09:46:49 AM · #11 |
Interesting read. Thanks for the link
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07/25/2008 09:55:20 AM · #12 |
I saw an article once, can't remember where, which graphed out the noise levels at each ISO for a few different sensors. It's been awhile, I'm sure it pre-dates the 40D. But the thing I noticed (besides the obvious "upward trend" in noise as the ISO increases), was that there were "bumps" along the way and that each of those bumps landed outside the normal 100-200-400-800-1600 levels.
In other words, instead of a straight diagonal line of progressively more noise from 100 to 200, the ISO's in between would be near the same level as 200. Then from 200-400 the ISO's in between would be near the same level as 400. And so on.
The explanation given was that for each of the standard ISOs, hardware circuitry does the amplification. But for the ISOs in between, there is a bit of "software interpolation" going on.
I don't know if that is still true in today's sensors ... but ever since that time, I mostly stick to the standard ISOs instead of ISOs such as 640 or 1000, etc. (i.e. if I need 640, I'll take it all the way to 800. If I need 1000, I'll take it all the way to 1600).
Something to think about. And if anyone else knows where to find that info, it might be good for an update.
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07/25/2008 10:19:05 AM · #13 |
Based on tests such as dpreview's (with the kind of graph david is refering to)
//www.dpreview.com/reviews/canoneos40d/page18.asp
noise always increases with iso. Which should logically be the case, for film or digital camera, no?
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07/25/2008 10:35:19 AM · #14 |
Originally posted by dwterry:
... I don't know if that is still true in today's sensors ... but ever since that time, I mostly stick to the standard ISOs instead of ISOs such as 640 or 1000, etc. (i.e. if I need 640, I'll take it all the way to 800. If I need 1000, I'll take it all the way to 1600). ... |
I do the same. I've noticed a big difference in noise performance when using the odd ISO's (640, 1000, 1250). I used to select auto ISO for action shooting and set either the shutter or aperture...not anymore, now I select the ISO and the shutter or aperture. |
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07/25/2008 10:58:40 AM · #15 |
at the extremes and with any NR function you lose detail and usually DR. I know on the 40D you lose alot of DR/Detail at 3200 compared to 1600. I've heard there is a similar issue on the 1D models that have the ISO 50 expansion on the low end but it's not as dramatic or noticeable.
There is hard measureable noise (i suppose) and then there is the 'quality' of the noise and one's taste or tolerance. I shoot up to 800 without concern about noise at all. Above 800 I watch my exposures very carefully.
I've shot studio work at 100, 200, 400 and 800 (and some in between) and can't say I've noticed any difference in sharpness or DR. At least on the 40D. Older bodies may show some issues. I do see some loss of detail at 1600 but for most things that's not much of an issue (like wedding ceremonies or receptions) but it's not my first choice for portraiture or landscapes, etc.
I'd not heard or thought about the 1/3 ISO stops and the noise being disproportionate but I'll have to check that out.
Message edited by author 2008-07-25 10:59:44.
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