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Author Topic: how many bracketed pictures for interior hdr processing?  (Read 35119 times)

Abdulrahman Aljabri

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how many bracketed pictures for interior hdr processing?
« on: July 01, 2015, 04:49:09 pm »

How many bracketed pictures do you take to do HDR for complex interior spaces? Also, what increments do you use? Can you get away with shooting 7 pictures at 1.6 stop increments and get the same quality HDR file as you have shot 11 pictures at 1 stop increments?

Thanks
« Last Edit: July 01, 2015, 05:01:29 pm by Abdulrahman Aljabri »
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AlterEgo

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Re: how man bracketed pictures for interior hdr processing?
« Reply #1 on: July 01, 2015, 04:56:46 pm »

How many bracketed pictures do you take to do HDR for complex interior spaces? Also, what increments do you use? Can you get away with shooting 7 pictures at 1.6 stop increments and get the same quality HDR file as you have shot 11 pictures at 1 stop increments?

Thanks

it was said that Fuji was using (in cameras like S5 Pro with "SuperCCD") 2 set of sensels, absolutely identical otherwise, but separated by 4 stops by a simple mask on top of one set /so the sensor was otherwise, underneath, a simple Sony one/ to reduce the amount of light reaching them... so  just 2 exposures separated by 4 stops shall do... and 3 will get you to absolute HDR nirvana of postprocessing... however which camera does allow 4 stops of separation in some automated mode ? so you can get by with 3 stops x 3 shots.
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Jimbo57

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Re: how many bracketed pictures for interior hdr processing?
« Reply #2 on: July 02, 2015, 08:48:51 am »

How many bracketed pictures do you take to do HDR for complex interior spaces? Also, what increments do you use? Can you get away with shooting 7 pictures at 1.6 stop increments and get the same quality HDR file as you have shot 11 pictures at 1 stop increments?

Thanks

Assuming that you want to use HDR processing simply to compensate for deficiencies in the dynamic range of your digital camera sensor (rather than to obtain the grotesque "HDR" effects that were a fad a few years ago), then the answer depends very much upon your own sensor. It is a matter in which considerable improvements have been made in recent years.

With my Nikon D810 I find that 2EV increments are adequate and I have yet to encounter a scene for which more than 5 exposures at 2EV increments was not sufficient. (Processing in Nik HDREfexPro from within Lightroom)
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Some Guy

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Re: how many bracketed pictures for interior hdr processing?
« Reply #3 on: July 02, 2015, 10:08:41 am »

Shooting 11 shots seems overkill, aside from eating up processing time.

I've been toying with the idea of using an Expodisc 2 and using it to determine my over and under shots for three exposures.  Might pay to use it and get the proper exposure spike in the middle of the camera's histogram, and then spin the shutter speed off until the spike is maybe 20% inwards on the left and right edge (i.e. Over & Under shots.) of the histogram?  That, theoretically, would allow for whatever oddities your sensor and your camera settings like Active-D lighting, etc. produce too.

If you were really good, you could also tune the three spikes with the WB and Tint Control as well to get the spike perfect without any RGB colors on the sides of the perfect spike indicating a WB error.

I might try this today on mine and see how this would work in practice for HDR speed settings on the D800E and older D7000.

Add:

I tried the above with the Expodisc 2.  Once I got the proper 4 seconds (ISO 250 at f/14 in a dark garage.) exposure, the D800E Over was 3 stops, and the Under was 4 stops and both spikes were still about 20% inside the histogram ends.  I would have thought 3 Over & 3 Under would place them in the same area near the ends, but +3 and -4 were the ones that worked and about 20% in at each end.  Not as linear as I would have thought, and these were long exposures:  30 seconds (+3 Over), 4 seconds (Normal), and 1/4 sec. (-4 Under).  Odd.  ???

SG
« Last Edit: July 02, 2015, 12:52:53 pm by Some Guy »
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Bart_van_der_Wolf

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Re: how many bracketed pictures for interior hdr processing?
« Reply #4 on: July 02, 2015, 10:47:04 am »

How many bracketed pictures do you take to do HDR for complex interior spaces? Also, what increments do you use? Can you get away with shooting 7 pictures at 1.6 stop increments and get the same quality HDR file as you have shot 11 pictures at 1 stop increments?

Hi,

It depends on how high your quality goal is, and if the subject has smooth gradients.

When the brightness transition of a smooth gradient is covered by two different exposures, then the difference of the Signal to Noise ratio of the exposures must not be too large. Otherwise the transition will become visible as a sudden jump in noise pattern, and is relatively easy to spot due to the lack of detail.

I've been able to push the exposure differential to two stops maximum, without running into trouble, but I routinely shoot at 1.33 stop intervals to be on the safe side when extra processing will amplify the differences. Usually 7 bracketed exposures is enough for very contrasty natural light situations, on a few occasions 1 or 2 extra exposures are welcome. 7 stops at a 1.33 EV interval, adds/replaces 9.3 stops of better quality dynamic range to the 11 - 13 that the camera already has and reduces the shadow noise to 1/3rd of the single exposure while adding some better (color and structure) detail. That's already a lot of improvement.

Cheers,
Bart
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Guillermo Luijk

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Re: how many bracketed pictures for interior hdr processing?
« Reply #5 on: July 02, 2015, 02:04:26 pm »

How many bracketed pictures do you take to do HDR for complex interior spaces? Also, what increments do you use? Can you get away with shooting 7 pictures at 1.6 stop increments and get the same quality HDR file as you have shot 11 pictures at 1 stop increments?

There is no fixed rule since it heavily depends on the blending software/method you use to mix your shots.

With optimal HDR software, more than 3 or 4 shots for ANY situation is just unnecessary, and 7 or 11 shots is just plain crazy. You'll not only get the same quality with 7 pictures at 1,6 intervals than with 11 at 1 stop intervals, but the same with 4 pictures at 3 stops intervals.

Unless your camera is very old, optimum software will be able to produce the same quality of results allowing 2-3 stops between shots. If your software is not optimum (e.g. Photomatix), ok you probably need more crazy shooting.

Regards
« Last Edit: July 02, 2015, 02:24:32 pm by Guillermo Luijk »
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ErikKaffehr

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Re: how many bracketed pictures for interior hdr processing?
« Reply #6 on: July 02, 2015, 03:15:34 pm »

Hi,

I think so. My cameras used to have ample DR, so I have seldom resorted to HDR. I would say that two exposures can be quite enough, one for the shadows and one for the highlights, perhaps a third one with "proper" exposure?

An earlier posting of mine may be worth checking: http://www.getdpi.com/forum/medium-format-systems-and-digital-backs/53815-testing-real-world-dynamic-range.html#post630479

Best regards
Erik


Can you get away with shooting 7 pictures at 1.6 stop increments and get the same quality HDR file as you have shot 11 pictures at 1 stop increments?

Thanks
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Guillermo Luijk

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Re: how man bracketed pictures for interior hdr processing?
« Reply #7 on: July 02, 2015, 04:18:15 pm »

it was said that Fuji was using (in cameras like S5 Pro with "SuperCCD") 2 set of sensels, absolutely identical otherwise, but separated by 4 stops by a simple mask

3,6 stops actually:




But those sensels weren't identical however. The highlight sensels (R) were much smaller:



The original article: FUJI SUPER CCD. IN CAMERA HDR

Regards


AlterEgo

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Re: how man bracketed pictures for interior hdr processing?
« Reply #8 on: July 02, 2015, 05:34:21 pm »

But those sensels weren't identical however. The highlight sensels (R) were much smaller:
well, for that I 'd assume you need to have an actual photo of the sensor layout, not a marketing illustration... simple logic says that it is much easier to deposit something that let "3.6EV" less light on surface of the regular Sony Semi manufactured CCD than bother to make a non standard (CCD on top of that) chip in low quantities (unless you are Sigma of course, and Fuji is not - but is well known by its games with toppings, like X-Trans).
« Last Edit: July 02, 2015, 05:38:22 pm by AlterEgo »
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haefnerphoto

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Re: how many bracketed pictures for interior hdr processing?
« Reply #9 on: July 05, 2015, 05:31:41 pm »

There is no fixed rule since it heavily depends on the blending software/method you use to mix your shots.

With optimal HDR software, more than 3 or 4 shots for ANY situation is just unnecessary, and 7 or 11 shots is just plain crazy. You'll not only get the same quality with 7 pictures at 1,6 intervals than with 11 at 1 stop intervals, but the same with 4 pictures at 3 stops intervals.

Unless your camera is very old, optimum software will be able to produce the same quality of results allowing 2-3 stops between shots. If your software is not optimum (e.g. Photomatix), ok you probably need more crazy shooting.

Regards


Guillermo, What software do you recommend?  Jim
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ErikKaffehr

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Re: how many bracketed pictures for interior hdr processing?
« Reply #10 on: July 06, 2015, 12:19:37 am »

Hi,

The HDR in LR6 is quite OK, I would say. LumaRiver HDR is another favourite of my.

Best regards
Erik

Guillermo, What software do you recommend?  Jim
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Guillermo Luijk

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Re: how many bracketed pictures for interior hdr processing?
« Reply #11 on: July 06, 2015, 08:53:33 am »

Guillermo, What software do you recommend?  Jim

I couldn't say since I use my own software for optimum blending (Zero Noise). SNS-HDR seems to work very well.

Regards

Ajoy Roy

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Re: how many bracketed pictures for interior hdr processing?
« Reply #12 on: July 06, 2015, 09:51:45 am »

How many bracketed pictures do you take to do HDR for complex interior spaces? Also, what increments do you use? Can you get away with shooting 7 pictures at 1.6 stop increments and get the same quality HDR file as you have shot 11 pictures at 1 stop increments?

Thanks

It all depends on the DR of the scene and the DR of the sensor. Most Nikon sensors have a DR of around 13 EV, of which 7 have very low noise. So in effect you can easily have steps of 2 EV. Now let us come to the DR of the scene. If you have a bright out side visible through the window and you want that and relatively dark interior, you can calculate the range, by using your meter in spot mode. Once point to the bright light outside and once to the dim light inside. What I do
. Assume the Light difference is 18 EV
. Assume that 2 EV steps are sufficient
. Assume that you want to use only 6 EV of your DR,
then
. The DR difference is 18-6 = 12
. Steps = 2 EV
. So shots required = 12/2 = 6

That way you will get absolutely clean shadows. In case you feel that the useful DR of sensor is 10EV instead of 6EV, you adjust the number of shots accordingly.
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caribsurf47

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Re: how many bracketed pictures for interior hdr processing?
« Reply #13 on: July 08, 2015, 04:40:09 am »

I have been shooting Bracketed images and using them for Tone Mapping since 2008 so I may have information about the technique that you may find useful.
In my humble opinion, unless you are a mathematician or a physicist I would not concern yourself with how Dynamic Range is calculated, I would stick to the photography. Assuming that you currently shoot with a DSLR. this is how I work and a methodology that produces consistent IQ:
1.   If at all possible, always shoot from a rigid tripod using the Mirror Lockup option and an electronic or Cable Release to shoot your frames
2.   Select the correct Aperture for the lens you are using and use as low an ISO as possible
3.   In poor light (in any light really), set the Focus manually using Live View plus Zoom or Focus Peaking if it is available i.e. switch off the Autofocus on the lens. In poor light many Camera Bodies in the low to mid range of a manufacturers range are compromised in their ability to "lock on" to subjects when shooting in a Burst Mode. In a burst of 8 to 10 frames a proportion of the frames may be "soft". You do not want ANY "soft" frames
4.   Use the appropriate Metering option on the camera to correctly expose for the brightest source of light in the scene you are capturing. This setting should be equivalent to your 0EV position
5.   Produce a range of RAW images around this 0EV position. I would suggest that you start by using -2EV, -1EV, +1EV and +2EV. I have seldom needed a greater range
6.   Take the five RAW frames into your Post Processing software and very carefully, fully process the 0EV frame such that the White Balance is correct and any blown highlights are treated. It is important that you treat any Digital Noise at this stage as well. Make sure that the processing Histogram stretches from the extreme left hand edge of the Y axis to the extreme right hand side of the Y axis (maximise the DR)
7.   Copy these settings and then apply them to all five frames
8.   Export the five images as 16-Bit TIFF files to your hard drive
9.   Begin by importing all five 16-Bit TIFF files into Photomatix Pro software and then use the Tone Mapping or Fusion option to produce an image
10.   An explanation of how to use Photomatix Pro software is too lengthy to include here so I will assume that you know what to do. As a guide line, if you are after a final end result more akin to the output available as Photo Merge to HDR in LR6, then stick with the options termed Balanced, Photographic and Neutral, which are displayed on the right hand side of the image displayed
11.   When you have adjusted the image as seen in the Photomatix Pro software to your satisfaction, click on Apply and use Save As to move the 16-Bit File to your hard drive
12.   Open the Tone Mapped or Fused 16-Bit File in Adobe Photoshop and then fine tune the end result as you would any other image
Note that I often select the minimum number of frames for processing in Photomatix Pro that result in the outcome that I want to achieve. More is not necessarily always best and usually the more frames that are combined, the more accentuated any Digital Noise becomes.
Do not be put off by the negative comments made about Photomatix Pro in this Post. I have found it to be excellent and certainly far more flexible in terms of what can be achieved VS Photo Merge to HDR in LR6 which is probably still more than enough for most people.

If you want any more information then send me an e-mail address so that any points can be addressed away from this Website. Inevitably there will be a proportion of people who see it differently and I don't have the time and the stomach to get embroiled in heated arguments. Hope this helps you. What I have described produces images of consistent quality time after time in my hands.
« Last Edit: July 08, 2015, 04:43:31 am by caribsurf47 »
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caribsurf47

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Re: how many bracketed pictures for interior hdr processing?
« Reply #14 on: July 08, 2015, 09:06:12 am »

It occurred to me that I have not posted an image to show you the Technique in action. Here is an image shot on Abermar Beach, Pembrokeshire, West Wales, Uk, in May this year. It uses three frames which have been processed with Photomatix Pro Vs. 5.0.5a. Here I have used the Canon EOS 5D Mark I with the Distagon T* 2.8/21 ZE at f/5.6 and ISO 200. It may look better viewed Fullscreen. I used Nik's Color Efex Pro 4 to finish off the image. It has made a fine print.
« Last Edit: July 08, 2015, 06:51:50 pm by caribsurf47 »
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nma

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Re: how many bracketed pictures for interior hdr processing?
« Reply #15 on: July 08, 2015, 01:54:44 pm »

Very nice image.

I would appreciate an explanation of how you approached the choice of 0 EV exposure in this image, referring to your previous post:  "Use the appropriate Metering option on the camera to correctly expose for the brightest source of light in the scene you are capturing. This setting should be equivalent to your 0EV position."

What would be the brightest source of light in this image? I assume you do not mean the setting sun but some other feature? What metering option did you choose and why?

thanks for your post and explanation
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caribsurf47

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Re: how many bracketed pictures for interior hdr processing?
« Reply #16 on: July 08, 2015, 06:24:48 pm »

Thanks for your enquiry. These RAW images are now archieved but I have got the external hard drive out of storage to remind me of how I produced this image.

I normally look at the BBC Weather Website to establish the exact time, by postcode, for either Sunset or Sunrise on the day I plan to shoot. I arrive at least 1 hour before the predicted time and set up the equipment for the shoot. The Camera/Lens is precisely leveled using a Manfrotto Hotshoe Spirit Level (the Canon EOS 5D Mark I does not have an inbuilt electronic levelling device), hence the position of the camera equipment is confirmed long before sunrise or sunset. From years of experience, I know that the Distagon T* 2.8/21 ZE produces its highest resolution corner to corner at an aperture of f/5.6 so this is set in Aperature Priority mode. Focus is then established manually and an appropriate ISO setting made, in this case I used ISO 200. The ISO reflects the balance between adequate Shutter Speed and the potential for Digital Noise. The lower the ISO used, normally the better. As the appointed time nears, I shoot a series of Frames at +1/3 increments up to +2EV using Centre Weighted Average Metering (from experience you will know that with the sun filling the majority of the frame, that the camera will tend to Underexpose the image. hence the + increments). I review each frame looking closely at the Highlight Alert and the shape of the Histogram. In the case of this sunset, +1 1/3 EV was the setting that was optimum in terms of offering the best Histogram and avoiding excessive highlight issues. At an appropriate time, when the disc of the sun was where I wanted it to be, I shot five Bracketed exposures at -2, -1 +1 and +2 EV either side of my theoretical optimum of +1 1/3 EV. From experience I know that I will get a decent final image from a combination of all or some of these Frames, it is trial and error. In the end I used only the - 2/3 EV + 1/3 EV and the the +1 1/3 EV Frames. The final image out of Photomatix Pro was fine tuned for Levels/Curves, Saturation etc. and Sharpened selectively for the foreground detail. I finished the processing in Nik's Color Efex Pro with the White Neutraliser as far as I can remember. Blue was also tweaked in the RGB area. I hope that you can make sense of this. Good luck with your photography. If I had been planning to use just a sinle RAW Frame for PP, then I would have worked only on the + 1 1/3 EV Frame. From experience I know that I will get a superior outcome using multiple frames into Photomatix Pro software. It is just my personal opinion of course and many, many others will cry foul for me using Photomatix Pro. Had I not told you then you would have been no wiser. By the way, for this image, the shutter speeds were good so the images were captured in bursts VS Mirror Lockup. I use Mirror Lockup mostly for architectural images, particularly indoors. If you still own a Nikon D700 or the Canon EOS 5D Mark I then don't get rid of it. Both cameras can still produce superb images if you maximise their strengths. Both cameras are vitually a steal second hand as most people belive that they will produce better images with higher Megapixel camera bodies. In reality this may not be the case as they are very much more technique dependent. Below is a Grab Shot of what the Histogram for the exposure selected to represent my baseline looks like. Bracketing -1EV and +1EV either side should be sufficient.
« Last Edit: July 10, 2015, 07:14:33 pm by caribsurf47 »
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caribsurf47

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Re: how many bracketed pictures for interior hdr processing?
« Reply #17 on: July 09, 2015, 04:41:16 am »

This is the view from the High Altar, through the Choir to the Nave inside the 11th century Winchester Cathedral, Hampshire, England. This uses 5 Frames. Distagon T* 2.8/21 ZE. Shot August 2013.
« Last Edit: July 09, 2015, 04:44:32 am by caribsurf47 »
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hubell

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Re: how many bracketed pictures for interior hdr processing?
« Reply #18 on: July 09, 2015, 07:42:04 am »

I have been shooting Bracketed images and using them for Tone Mapping since 2008 so I may have information about the technique that you may find useful.
In my humble opinion, unless you are a mathematician or a physicist I would not concern yourself with how Dynamic Range is calculated, I would stick to the photography. Assuming that you currently shoot with a DSLR. this is how I work and a methodology that produces consistent IQ:

4.   Use the appropriate Metering option on the camera to correctly expose for the brightest source of light in the scene you are capturing. This setting should be equivalent to your 0EV position
5.   Produce a range of RAW images around this 0EV position. I would suggest that you start by using -2EV, -1EV, +1EV and +2EV. I have seldom needed a greater range
6.   Take the five RAW frames into your Post Processing software and very carefully, fully process the 0EV frame such that the White Balance is correct and any blown highlights are treated. It is important that you treat any Digital Noise at this stage as well. Make sure that the processing Histogram stretches from the extreme left hand edge of the Y axis to the extreme right hand side of the Y axis (maximise the DR)


If you want any more information then send me an e-mail address so that any points can be addressed away from this Website. Inevitably there will be a proportion of people who see it differently and I don't have the time and the stomach to get embroiled in heated arguments. Hope this helps you. What I have described produces images of consistent quality time after time in my hands.


I am curious why, if you are metering for the brightest source of light in the scene as your "base" exposure, you are shooting frames at -1 and -2EV. Also, if the base exposure is metered for the brightest source of light in the scene, why would the highlights be "blown"?

caribsurf47

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Re: how many bracketed pictures for interior hdr processing?
« Reply #19 on: July 09, 2015, 09:00:42 am »

If you are shooting an architectural interior, say for example inside a cathedral looking up the Nave to the Altar, you will be presented very often with multiple light sources, a large area of glass behind the altar and very often oblique lighting from high up in the vaulted roof and in addition artifical lighting, sometimes pointing directly at the camera i.e. these are difficult images to shoot. You may be using Centre Weighted Average Metering and that will give you a starting point but you will be wise to take a series of frames at + and/or - 1/3EV steps and review the resulting images on the back of the camera. You will be looking at the shape of the Histogram and for the subtle changes that these incremental adjustments have made.

The second point is that if you are shooting in a Bracketed Mode, you will have to accept the fact that the camera will shoot either side of your optimum EV i.e. it will automatically shoot at +EV Fame and a  -EV Frame.

Thirdly, as mentioned in one of my previous posts, it is very useful to have these frames as you may get a superior result by using only a few of the exposures in Photomatix Pro i.e. a Mix and Match approach

Don't get too bogged down in these technicalities as you can still repair problem areas of the Tone Mapped image in Photoshop at the end if you have to, but it helps not to have a totally compromised starting image coming out of the Tone Mapping process. I hope that you can understand what I am trying to explain. It just works for me 99% of the time. Just run with the basic ideas and see what you get.
« Last Edit: July 09, 2015, 09:39:31 am by caribsurf47 »
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