Ad
Ad
Ad
Pages: « 1 2 3 [4] 5 »   Bottom of Page
Print
Author Topic: Michael Reichmann, ETTR and Oly OMD EM5  (Read 21228 times)
BJL
Sr. Member
****
Offline Offline

Posts: 5124


« Reply #60 on: January 07, 2013, 02:52:11 PM »
ReplyReply

thanks, no I mean RAW

will post examples when I figure out how you guys do the posting of such large files to this site...
As an EM5 user who has followed the debate over its "sensitivity", this is very intriguing!

Apart from trying to post examples, can you say how you are choosing exposure levels when this overexposure occurs? With in-camera metering in aperture priority mode? If so, with which metering mode? (I am trying to work out some weird abberations with its multi-pattern metering mode, especially with adaptor mounted SLR lenses, so center weighted has been far safer with those old lenses.)

Or are you using an external light meter set to the same ISO exposure index as the EM5s ISO sensitivity setting?

Also, how are you converting from raw to the RGB files in which you see overexposure? (Or are you looking directly at level placement in the raw files?)
Logged
allegretto
Sr. Member
****
Offline Offline

Posts: 399


« Reply #61 on: January 08, 2013, 09:37:22 PM »
ReplyReply

all fair questions

just using center weighted and manual ISO settings

very busy week professionally (not a photographer), dont mean to be a dyk, will get the images
Logged
BJL
Sr. Member
****
Offline Offline

Posts: 5124


« Reply #62 on: January 09, 2013, 08:52:32 AM »
ReplyReply

Thanks.
    I look forward to your sample images, but no hurry ... after all, I am testing my newish EM5 myself, but appreciate additional info. from other users in this forum.

all fair questions

just using center weighted and manual ISO settings

very busy week professionally (not a photographer), dont mean to be a dyk, will get the images
Logged
Jack Hogan
Full Member
***
Offline Offline

Posts: 219


« Reply #63 on: January 10, 2013, 11:30:46 AM »
ReplyReply

What I'm asking (for the E-M5) is, assuming I've set optimum aperture and shutter speed, is it a good idea in terms of image quality to increase ISO to just below the clipping point (where clipping is determined by blinkies, as Michael stated), so long as you don't go above 1600?

This excellent chart by Bill Claff suggests that after ISO 400 you get very little IQ improvement raising the ISO on an EM5 - I would stop thereabouts because every time you raise the ISO by one stop you reduce highlight headroom by the same amount.  For instance if you are 'properly' ETTR'd at ISO1600, you only gain about 0.1 of a stop in noise performance compared to ISO 400 (I challenge you to see the difference :-), but you give up two stops of highlight headroom.  Of course in such a situation ISO 400 most likely entails correcting brightness in post.

Different story for Canons, as you can see...
« Last Edit: January 10, 2013, 11:36:11 AM by Jack Hogan » Logged
allegretto
Sr. Member
****
Offline Offline

Posts: 399


« Reply #64 on: January 12, 2013, 03:07:25 PM »
ReplyReply

How does one post a true RAW file here? I have RX1 and OM-D shoot off here but don't know how to get the full sized files uploaded. Will only take up to 5Meg.

Thanks...
Logged
stamper
Sr. Member
****
Offline Offline

Posts: 2631


« Reply #65 on: January 13, 2013, 05:28:40 AM »
ReplyReply

I think you will have to us a site like this.

http://www.mediafire.com/about/

and then post a link that anyone can download. It has a free subscription.
« Last Edit: January 13, 2013, 05:30:59 AM by stamper » Logged

gerafotografija
Full Member
***
Offline Offline

Posts: 224



WWW
« Reply #66 on: January 14, 2013, 12:24:42 AM »
ReplyReply

This excellent chart by Bill Claff suggests that after ISO 400 you get very little IQ improvement raising the ISO on an EM5 - ...

Although I am generally scientifically inclined, I would have to brush up on light detector physics and engineering to add to the quantitative debate. After reviewing various sensor performance curves with the tool linked to above, it looks to me like the sensor generations seem to be progressing to a flatter curve, but it is not clear to me whether that represents an improvement or not.

However, having put a few thousand frames of captures through my OMD, maybe the following highly subjective and aesthetically directed comments may provide useful input? Someone else may be available to explain to me why I am doing these things, and whether there are better choices.

My first inclination was to use the OMD at base iso whenever possible, because the colors come out absolutely gorgeous and if you ettr and botch it up there is headroom to recover quite a bit in pp (Aperture 3 recovery in my case). You could argue that specific good color examples may have also been due to good lighting, or good lens drawing, or post processing for optimal curves, but I have personally never been able to "nail" the color tones and ranges so easily with any camera previously. Admittedly I gave it a shot with Kodachrome and Velvia back in the day.

That said, when I get to iso 1600 and beyond, I start to think about converting to monochrome because the colors start to go wrong. I can still get reasonable results at 1600 and with NR up to ~4000, but it no longer looks natural, and if there is skin involved, a careful B&W treatment with virtual red or yellow filtering added keeps the image reasonably flattering if not ideal.

Now that I have digested this thread a bit, my recent and completely unrelated switching to auto iso with a limit of 400 or 800 in less than perfect lighting conditions makes sense a bit. Keep in mind that I am mainly an enthusiastic amateur working with ambient lighting, and only rarely supplementing it with fill flash or other sources. The reason I switched to auto iso was to still get good colors across the DR (shadow through highlights), but in less than ideal conditions. I have never felt the need for NR up to 400 or so with this camera after getting a reasonable exposure, and usually a light touch of denoising at 800 with moderate at 1600, and then nothing but B&W along with heavier NR above that. This upper end is probably the range of conditions that moved me to switch over to and then push process Tri-X 10 to 20 years ago.

Assuming the sensor at different gains keeps the Rs Gs and Bs looking the way my eyes expect them to be as the overall luminance drops, I am with the group that proposes to push iso whenever possible to get the histogram to push all the way to the right. If my rods and cones start to diverge with respect to what they expect to be seeing on the screen or print, and I start to see bias or artifacts rather than natural (or at least pleasing or useful) renditions of colors and textures, that triggers a different approach to the image in pp and a slightly different plan during capture I tend to focus my attention on mid-tones when exposing for monochrome.

I have no idea whether the base iso vs higher iso comparisons proposed take any of these aspects of IQ into account, but you can be sure I will be following along closely to see if I can learn a way to wring out another eV or so of useful range out of this sensor.
Logged

richarddd
Jr. Member
**
Offline Offline

Posts: 86


« Reply #67 on: January 14, 2013, 08:22:40 AM »
ReplyReply

This excellent chart by Bill Claff suggests that after ISO 400 you get very little IQ improvement raising the ISO on an EM5 - I would stop thereabouts because every time you raise the ISO by one stop you reduce highlight headroom by the same amount.  For instance if you are 'properly' ETTR'd at ISO1600, you only gain about 0.1 of a stop in noise performance compared to ISO 400 (I challenge you to see the difference :-), but you give up two stops of highlight headroom.  Of course in such a situation ISO 400 most likely entails correcting brightness in post.
If you are below clipping, why do you need more highlight headroom?
Logged

richarddd
Jr. Member
**
Offline Offline

Posts: 86


« Reply #68 on: January 14, 2013, 08:29:29 AM »
ReplyReply

I have no idea whether the base iso vs higher iso comparisons proposed take any of these aspects of IQ into account, but you can be sure I will be following along closely to see if I can learn a way to wring out another eV or so of useful range out of this sensor.
I worry that we focus too much on quantitative measures that don't capture all technical aspects of image quality.  To take a random example, it makes a difference whether or not noise has patterns.
Logged

Jack Hogan
Full Member
***
Offline Offline

Posts: 219


« Reply #69 on: January 14, 2013, 10:43:51 AM »
ReplyReply

If you are below clipping, why do you need more highlight headroom?
Good question.  I would turn it around: how many times have we blown highlights that we wished to keep?  It's an almost free lunch: the extra DR costs virtually nothing - except perhaps a little EC in post :-)
Logged
Jack Hogan
Full Member
***
Offline Offline

Posts: 219


« Reply #70 on: January 14, 2013, 11:12:57 AM »
ReplyReply

Assuming the sensor at different gains keeps the Rs Gs and Bs looking the way my eyes expect them to be as the overall luminance drops...

I have no idea whether the base iso vs higher iso comparisons proposed take any of these aspects of IQ into account, but you can be sure I will be following along closely to see if I can learn a way to wring out another eV or so of useful range out of this sensor.

The answer depends on two separate components: the sensor, and the raw converter.  As far as the sensor goes, since it is based on Exmor technology which is quite linear with virtually no pattern noise, it should make no difference whatsoever to your rods and cones as long as the raw data is properly rendered - which brings us to the raw converter.   Most don't have a problem brightening up tones two or three stops.  If pushed hard, LR supposedly may exhibit issues because it 'Does the Twist'.  I don't think this should be an issue for the EM5, but perhaps someone will let us know?

Cheers Jack
Logged
richarddd
Jr. Member
**
Offline Offline

Posts: 86


« Reply #71 on: January 14, 2013, 12:00:12 PM »
ReplyReply

Good question.  I would turn it around: how many times have we blown highlights that we wished to keep?  It's an almost free lunch: the extra DR costs virtually nothing - except perhaps a little EC in post :-)
Sure, but my line in this thread is whether this is a productive technique:

1) Increase exposure until the first of (a) edge of clipping in highlights we wish to keep and (b) too slow shutter speed or too deep depth of field

2) If not yet at clipping, increase ISO until the first of (a) edge of clipping in highlights we wish to keep and (b) 800 or 1600

Practical application depends on being able to detect clipping, but the E-M5's orange highlight blinkies seem adequate (as MR says in the beginning of this thread).

In this technique, we will not blow highlights we wish to keep, by definition, so loss of highlight headroom would not be an objection.

If one is not prepared for a little adjustment in post, one shouldn't be shooting RAW :-)
« Last Edit: January 14, 2013, 03:05:47 PM by richarddd » Logged

Jack Hogan
Full Member
***
Offline Offline

Posts: 219


« Reply #72 on: January 14, 2013, 04:16:09 PM »
ReplyReply

2) If not yet at clipping, increase ISO until the first of (a) edge of clipping in highlights we wish to keep and (b) 800 or 1600

Right, great technique.  And my suggestion, after perusing Bill Claff's chart for the EM5, is however b) 400.

Cheers,
Jack
« Last Edit: January 14, 2013, 04:21:19 PM by Jack Hogan » Logged
richarddd
Jr. Member
**
Offline Offline

Posts: 86


« Reply #73 on: January 15, 2013, 07:56:46 AM »
ReplyReply

Right, great technique.  And my suggestion, after perusing Bill Claff's chart for the EM5, is however b) 400.
As I read the charts, by going from 400 to 800 or 1600, you improve noise at the cost of decreased dynamic range.  Decreased noise is a good thing, while decreased DR should not hurt if you are not in highlight clipping range.

Do you disagree with this analysis or is there another factor I'm ignoring?

BTW, increasing exposure (light on sensor) is always a good thing, so long as you're not clipping (or using too slow a shutter speed or too shallow DOF). Increasing ISO is more about trade-offs, primarily between noise and DR as I understand it.
Logged

Jack Hogan
Full Member
***
Offline Offline

Posts: 219


« Reply #74 on: January 15, 2013, 09:44:18 AM »
ReplyReply

As I read the charts, by going from 400 to 800 or 1600, you improve [minimally] noise at the cost of  [1 or 2 stops of] ... dynamic range.  Decreased noise is a good thing, while decreased DR should not hurt if you are not in highlight clipping range.

Do you disagree with this analysis or is there another factor I'm ignoring?

That's basically it, and I agree with your statement as modified above.

Quote
BTW, increasing exposure (light on sensor) is always a good thing, so long as you're not clipping (or using too slow a shutter speed or too shallow DOF). Increasing ISO is more about trade-offs, primarily between noise and DR as I understand it.

Yes, but in the fine technique that you have outlined, exposure is always maximized according to artistic constraints first - and it doesn't change one bit (it stays maximized) when you raise the in-camera ISO setting.   The benefit in SNR obtained by raising ISO has nothing to do with exposure and all to do with the sensor electronics: increasing ISO in some cameras results in reduced sensor read noise.  If you look at the chart by Bill Claff you'll realize that for Canon sensors your statement just above is relatively accurate but for a so-called ISOless sensor such as the D7000's it is not because b) in your procedure above would be base ISO, so by raising ISO all you'd be doing is lowering the clipping point of the recorded data (while maintaining the exact same exposure) - no benefits whatsoever.

Back to your EM5, which is ISOless above 1200.  I can see a SNR benefit going from 200 to 400.  From 400 to 1200 you gain very little (1/6 of a stop of SNR - I challenge you to see it :-) while reducing the clipping point 1.5 stops: is it worth the risk?  Your camera, your scene, your call.  Past that, though, you only have something to lose by raising ISO.

Just out of curiosity, if you had a D7000, would you feel comfortable setting blur and dof (that is shutter speed and f/number, that is exposure) according to your procedure and artistic intent and leaving ISO at base forever, forgetting it even existed?  Your exposure would be the same than otherwise, your IQ would not suffer one bit Smiley and you'd have the best DR in town.  Nevertheless some people just do not feel comfortable getting properly exposed, dark images OOC.

Jack
« Last Edit: January 15, 2013, 09:53:20 AM by Jack Hogan » Logged
richarddd
Jr. Member
**
Offline Offline

Posts: 86


« Reply #75 on: January 15, 2013, 02:50:15 PM »
ReplyReply

I agree that the benefits of pushing ISO decrease rapidly above 400 on the E-M5.

I don't have a D7000 or other DSLR.  From what I've read, leaving ISO at base and adjusting in post works well with modern Nikon DSLRs, other than that it makes it hard to review pictures in camera, as the image on the LCD is often too dark.

Logged

digitalphotographer
Newbie
*
Offline Offline

Posts: 5


« Reply #76 on: September 11, 2013, 10:37:12 PM »
ReplyReply

This excellent chart by Bill Claff suggests that after ISO 400 you get very little IQ improvement raising the ISO on an EM5 - I would stop thereabouts because every time you raise the ISO by one stop you reduce highlight headroom by the same amount. 

Thanks for the suggestion for the EM5! In this case, it seems limiting Auto-ISO to ISO400 and doing manual "push" or EV adjustments in LR/ACR will be a better option to have more highlights headroom and controls, am I right?

Just want to make sure I understand this, when the ISO is top-limited at 400, I will still get benefits from ETTR, is this correct?
Logged
bjanes
Sr. Member
****
Offline Offline

Posts: 2772



« Reply #77 on: September 12, 2013, 06:26:03 AM »
ReplyReply

I agree that the benefits of pushing ISO decrease rapidly above 400 on the E-M5.

I don't have a D7000 or other DSLR.  From what I've read, leaving ISO at base and adjusting in post works well with modern Nikon DSLRs, other than that it makes it hard to review pictures in camera, as the image on the LCD is often too dark

Contrary to popular belief, the Nikon D800 is not really ISOless and some improvement in shadow performance can be obtained by increasing the ISO, but the effect is relatively small, less than 1/2 stop as shown by Bill Claff's previously mentioned graph.

A basic understanding of the sources of noise in digital captures is helpful and Emil's post is an excellent source. The two main sources of noise are shot noise (which is predominant in the highlights) and read noise (which predominates in the deep shadows). We are not interested in noise per se, but in the signal to noise ratio. Shot noise is maximal in the highlights, but the SNR increases as the square root of exposure.

Read noise predominates in the deep shadows. In cameras where the electronics (primarily the analog to digital converter) is not well matched to the full well capacity of the sensor (such as with most Canons), read noise can be reduced by increasing the ISO gain. If f/stop and shutter speed considerations prevent attaining full well, one can increase the ISO gain with the Canon to get a better DR. However, head room is decreased and one can clip the highlights if the ETTR is overdone. With the D800e, the DR improvement is less than 1/2 stop with ETTR under these conditions, but the risk of highlight clipping remains.

Thermal noise is important in astrophotography, but is minimal  with exposures of less than a second, so it is not important to cool the sensor with ordinary terrestrial photography.

The presumed increase in tonality towards the right end of the histogram where more levels are present is largely a red herring, since these potential levels are dithered by noise and effectively obliterated, as explained by Emil in some detail.

Bill



Logged
Vladimirovich
Sr. Member
****
Offline Offline

Posts: 1320


« Reply #78 on: September 12, 2013, 09:44:09 AM »
ReplyReply

Thanks for the suggestion for the EM5! In this case, it seems limiting Auto-ISO to ISO400 and doing manual "push" or EV adjustments in LR/ACR will be a better option to have more highlights headroom and controls, am I right?
you are not getting more "highlights headroom" with a higher gain... higher gain makes sense if you want to get better SNR (Signal/Noise) in (deep) shadows if the scene's total DR and your intent in terms of what you can tolerate to be clipped in raw will allow you to increase the gain...
Logged
digitalphotographer
Newbie
*
Offline Offline

Posts: 5


« Reply #79 on: September 12, 2013, 02:12:21 PM »
ReplyReply

you are not getting more "highlights headroom" with a higher gain... higher gain makes sense if you want to get better SNR (Signal/Noise) in (deep) shadows if the scene's total DR and your intent in terms of what you can tolerate to be clipped in raw will allow you to increase the gain...
Thanks for the clarification. What I meant to say was, when shooting EM5 at max ISO 400 and using ETTR, I will have more highlight headroom than shooting at ISO800 or ISO1600, with the benefit of reducing shadow noise on the RAW files. Is this understanding correct?
Logged
Pages: « 1 2 3 [4] 5 »   Top of Page
Print
Jump to:  

Ad
Ad
Ad