Ad
Ad
Ad
Pages: « 1 2 3 [4]   Bottom of Page
Print
Author Topic: DxOMark's new resolution magnitude: P-Mpix  (Read 7420 times)
BJL
Sr. Member
****
Offline Offline

Posts: 5129


« Reply #60 on: November 26, 2013, 10:01:29 AM »
ReplyReply

Probably I didn't say that clearly enough, but my question to you was rather specific and not about Ray's situation. It was simply: Is there a difference in IQ of the resulting image between the two situations where you shoot 1) one picture at ISO 100 and underexposed by zero to e.g. 6 stops and 2) the same picture shot at ISO settings 100, 200, 400 and 6400? Again assuming no highlight clipping.
I think we are essentially in agreement, but just to clarify ...

Last point first; the only potential benefit that I am claiming for this procedure of using less analog gain is to avoid highlight clipping, so that last assumption is a bit weird!

But indeed, I find it hard to imagine a situation where four stops of under-amplification (100 vs 1600) would be needed to avoid amplifier clipping of highlights, which is why I prefer a middle ground of placing the raw levels one or two stops below "normal" and flagging that placement in the metadata. But perhaps Ray can find an example where his light metering or exposure settings were off by a full four stops and clipped some highlights!

Also, I have repeatedly talked about under amplifying to about ISO 400 with cameras like Nikons, not all the way down to ISO 100, because from what I have read, there could be some benefit in reduced quantization noise and thus reduced posterization in raising the gain that far. So your 100 vs 1600 experiment is not relevant to my comments, but might be relevant to the more extreme "minimal amplification" approach described by Ray. (The one situation I know of where it might be good to always use the same "base ISO" amplifier gain is with some combinations of Kodak CCDs and good 16-bit off-board ADCs, where that gain already puts sensor/read noise well above the ADC's quantization noise level.)

Btw. the 16x shift, I assume you mean 4x shift (shifting bits 4 positions) going from ISO 100 to ISO 1600.
Yes, 16x means shifting the values by multiplying by a factor of 16, so shifting four bits to the left.
« Last Edit: November 26, 2013, 10:05:25 AM by BJL » Logged
Ray
Sr. Member
****
Offline Offline

Posts: 8884


« Reply #61 on: November 26, 2013, 05:43:39 PM »
ReplyReply

There are at least two major disadvantages to the method of shooting at ISO 100 and allow underexposure 1) You can't even see the pictures on the LCD, you can't review focus or show it to anyone 2) you have to adjust exposure when importing into Lightroom or any other RAW converter before you can review the pictures for selection or rejection.

Hans,

First let me congratulate you on your spectacular landscape images on your linked site.
Now to business. Grin

I've already agreed there is a disadvantage in not being able to share the images with anyone on the camera's LCD screen. However, if one was attempting to capture the moment, the ability to review the image for focus and other issues is not likely to serve much purpose. Would Cartier-Bresson have found the ability to review his shots useful? Refer attached image. Wink

The extra work of adjusting exposure in the RAW converter before determining whether or not to delete an image is trivial for me. By far the greater proportion of my rejects over the years have been those taken in Aperture Priority mode when the automatic selection of shutter speed has been too slow to freeze movement or too slow to avoid blown highlights in parts of the scene that I considered important.

It is this very preponderance of such rejects that has led me to this approach of using the camera as though it were ISO-less. Nevertheless, I accept there are small, incremental losses in image quality, compared with using a 'correct' ISO in relation to an ETTR, which might be noticeable if the underexposure is taken to extremes.

For me it's really a trade-off between the two concerns of (1) getting the shot with a confidence that there will be nothing seriously wrong that will cause it to be a reject, and (2) missing  the moment entirely as a result of spending too much time making camera adjustments to ensure maximum image quality.

Your approach of using auto-ISO should be better when using extreme underexposure. I'll give it a try. My main concern is that there appears to be no indication in the D7100 viewfinder of underexposure when a minus value of EC is enabled.

Quote
Check the examples of my ISO 6400 test I have just posted. Try it with your D7100 and it will likely be much worse.

Now, Hans, you are getting a bit tricky. Grin  I mentioned specifically that Nikon is going backwards with regard to the ISO-less nature of their most recent models, including the D800 and the D7100. A consequence of this is that one should try to avoid using ISO 100 when underexposing. You've not only used ISO 100, but given 6 stops of underexposure as well.This is what I wrote earlier, in reply to BJL:

Quote
If we compare the DXO measurements for the D7100, we find that the ISO-less nature is not quite as good as that of the D7000 and is best within a narrower range of ISOs, specifically from ISO 200 to ISO 1600, which represents the 3 stops underexposure that I used in my above shot of the mule.

Just to confirm that I am correct in this view that there should be no significant problem in underexposing by 3 stops at ISO 200 with the D7100 (apart from possible banding), I took the following shots just after sunrise this morning, Australian time.

Perhaps I should not have labelled these shots, and should have asked you to guess which was taken at ISO 200. I simply cannot discern any differences at 100% view that would indicate that one of the shots was an underexposure in relation to its ISO setting. Can you?

I should also point out that I have made no adjustments to either of these images apart from raising the exposure of the underexposed shot to +3 in ACR, and apart from letting the default sharpening of 25 apply to both images. The conversions are from the settings that appear in the attached screen capture of the ACR window, with no further adjustment in Photoshop.

Logged
Torbjörn Tapani
Jr. Member
**
Offline Offline

Posts: 66


« Reply #62 on: November 26, 2013, 06:17:30 PM »
ReplyReply

Hans,

First let me congratulate you on your spectacular landscape images on your linked site.

Ray, I would like to thank you for pointing this out. And Hans, what a fantastic set of images you got there!
Logged
BJL
Sr. Member
****
Offline Offline

Posts: 5129


« Reply #63 on: November 26, 2013, 08:41:55 PM »
ReplyReply

Ray, I would like to thank you for pointing this out. And Hans, what a fantastic set of images you got there!
Indeed! I was almost tempted to comment on this debate yet again, but then decided it is far better to sit back and look at those beautiful photographs. It is edifying, though a bit humiliating, to see photographs of scenes that I have also visited (some of those sites in the Dolomites) that are so much better than anything I achieved there.
« Last Edit: November 26, 2013, 08:47:46 PM by BJL » Logged
Hans Kruse
Sr. Member
****
Offline Offline

Posts: 706



WWW
« Reply #64 on: November 27, 2013, 12:28:34 PM »
ReplyReply

Hans,

First let me congratulate you on your spectacular landscape images on your linked site.
Now to business. Grin


Thanks very much Smiley

Quote

I've already agreed there is a disadvantage in not being able to share the images with anyone on the camera's LCD screen. However, if one was attempting to capture the moment, the ability to review the image for focus and other issues is not likely to serve much purpose. Would Cartier-Bresson have found the ability to review his shots useful? Refer attached image. Wink


He didn't need that for sure for this shot. For me it would be a major disadvantage if I could look at my shots, but if that does not really mean anything to then this item is out.

Quote


The extra work of adjusting exposure in the RAW converter before determining whether or not to delete an image is trivial for me. By far the greater proportion of my rejects over the years have been those taken in Aperture Priority mode when the automatic selection of shutter speed has been too slow to freeze movement or too slow to avoid blown highlights in parts of the scene that I considered important.


When using aperture priority and auto ISO, I always make sure to have set a minimum shutter speed. That's on my Canon since I can't use exposure compensation in manual mode on the Canon.

Quote

It is this very preponderance of such rejects that has led me to this approach of using the camera as though it were ISO-less. Nevertheless, I accept there are small, incremental losses in image quality, compared with using a 'correct' ISO in relation to an ETTR, which might be noticeable if the underexposure is taken to extremes.

For me it's really a trade-off between the two concerns of (1) getting the shot with a confidence that there will be nothing seriously wrong that will cause it to be a reject, and (2) missing  the moment entirely as a result of spending too much time making camera adjustments to ensure maximum image quality.

Your approach of using auto-ISO should be better when using extreme underexposure. I'll give it a try. My main concern is that there appears to be no indication in the D7100 viewfinder of underexposure when a minus value of EC is enabled.


If you are unsure you only need to push the EC button. Alternatively you could set bracketing to two exposures one stop apart which would result in a -1 and a -2 and set the camera to continous shooting so when you hold down the shutter button it will fire off 2 shots immediately. On my Canon 5D III I use bracket one stop apart and 3 and set to continous shooting it will fire off 3 shots rapidly and I can always shoot again. I can set exposure compensation to -1 which results in -2, -1 and 0 EC and I very seldomly will have blown out essential parts of my photos. I will notice the ISO's chosen form time to time when lighting changes a lot like indoor and I will change aperture to the minimum required for DOF. I usually with my 24-70 set the minimum shutter speed to 1/125 but sometimes to 1/60. I get sharp focused results and good IQ (even from a Canon Smiley) and I don't have to check histograms and can fire away and I can see my shots on the LCD. I don't really loose any shots this way except where I should use a tripod, but then this is casual shooting and I don't bring a tripod in this case.

Quote


Now, Hans, you are getting a bit tricky. Grin  I mentioned specifically that Nikon is going backwards with regard to the ISO-less nature of their most recent models, including the D800 and the D7100. A consequence of this is that one should try to avoid using ISO 100 when underexposing. You've not only used ISO 100, but given 6 stops of underexposure as well.This is what I wrote earlier, in reply to BJL:


I thought you were referring mainly to the D7100 as the D800 is not that recent Smiley But anyway look at the attached DxO chart of the D800, D610 and D7100 and notice that the recent D610 is as good and even better than the D800 at the pixel level for DR. And yes there is a little drop from linearity between ISO 100 and 200. Notice also my other posts on Lightoom processing of less than 6 stops and that there is an issue with Lightroom and ACR lifting more than 4 stops in exposure.

Quote


Just to confirm that I am correct in this view that there should be no significant problem in underexposing by 3 stops at ISO 200 with the D7100 (apart from possible banding), I took the following shots just after sunrise this morning, Australian time.

Perhaps I should not have labelled these shots, and should have asked you to guess which was taken at ISO 200. I simply cannot discern any differences at 100% view that would indicate that one of the shots was an underexposure in relation to its ISO setting. Can you?


No, they look pretty much the same to me.

Quote


I should also point out that I have made no adjustments to either of these images apart from raising the exposure of the underexposed shot to +3 in ACR, and apart from letting the default sharpening of 25 apply to both images. The conversions are from the settings that appear in the attached screen capture of the ACR window, with no further adjustment in Photoshop.


Logged

Hans Kruse
Sr. Member
****
Offline Offline

Posts: 706



WWW
« Reply #65 on: November 27, 2013, 12:31:12 PM »
ReplyReply

Indeed! I was almost tempted to comment on this debate yet again, but then decided it is far better to sit back and look at those beautiful photographs. It is edifying, though a bit humiliating, to see photographs of scenes that I have also visited (some of those sites in the Dolomites) that are so much better than anything I achieved there.

Thanks very much. But don't forget that I have been visiting the Dolomites two to four times a year since 2009 Smiley It has been a lot of time and hard work. Now I do 4 workshops per year in the Dolomites which gives me a lot of time to shoot.
Logged

Hans Kruse
Sr. Member
****
Offline Offline

Posts: 706



WWW
« Reply #66 on: November 27, 2013, 12:32:34 PM »
ReplyReply

Ray, I would like to thank you for pointing this out. And Hans, what a fantastic set of images you got there!

Thanks very much!
Logged

Pages: « 1 2 3 [4]   Top of Page
Print
Jump to:  

Ad
Ad
Ad