HDR for beginners

gnolan

I was out last night and took five shots that i want to merge to HDR. I believe i went about it the right way:

1. I shot one image with the light meter at 0 (at the center) at f/18.

2. I then took 4 more shots at f/20, f/22, f/16 and f/14, is this correct

3. I had read that the white balance should not be set to auto so i changed it to shade, everything has an orange tint to it but i believe i can take this off in PP.

I'm just wondering whether i missed out on anything. I had the camera set to auto-focus each time, which i'm thinking may have been a bad idea; but i think it picked the same focus point for each shot.

Now that i think of it, i had VR on which i probably shouldn't have considering i had a tripod.

There doesn't seem to a huge difference in lighting in the shots i took, should i be taking bigger steps up and down with the aperture, or should i leave the aperture be and change the exposure time?

Would it be a good idea to alter the exposure in PP before merging to HDR?

I'd appreciate any tips or tricks that people could offer.

5uspect

You should be shooting in M (or Av) and leave the aperture alone and only change the exposure.

If you are going to do HDR you should be shooting RAW for the reasons explained to you in the other thread. You can tone map a single RAW file to fill light in the darks, recover detail in the highlights.

HDR = High Dymanic Range, RAW files have lots of it and usually enough for most scenes.

pullandbang

There won't be a huge difference in the exposure of your shots as you've only bracketed by just over 1 full stop across your 5 shots - f14 to f22.

f16 down to f22 is one full stop. You need to bracket by at least two full stops - one below and one above your mid point.

And yes, don't forget to knock off your VR / IS when using a tripod.

gnolan

5uspect wrote: »

You should be shooting in M (or Av) and leave the aperture alone and only change the exposure.

If you are going to do HDR you should be shooting RAW for the reasons explained to you in the other thread. You can tone map a single RAW file to fill light in the darks, recover detail in the highlights.

HDR = High Dymanic Range, RAW files have lots of it and usually enough for most scenes.

Well i was shooting in M and RAW which i suppose is a good thing. So in future i'll leave the aperture be and change the exposure time. Once i've focussed the intial shot should i change to manual focus so it doesn't try to refocus on another point.

Again, i wouldn't be familiar yet with tone-mapping - i assume i would do this in Photoshop? For the shots i took last night, would i get decent results by changing the exposure in post processing to give more of a contrast between the images?

One more question about this. When i open the RAW in Photoshop, will it not cease to be a RAW file and become a PSD? When editing each individual RAW in Photoshop, do i perform my edits and just save as .NEF? Will i lose any significant amount of data in doing this?

pullandbang wrote: »

There won't be a huge difference in the exposure of your shots as you've only bracketed by just over 1 full stop across your 5 shots - f14 to f22.

f16 down to f22 is one full stop. You need to bracket by at least two full stops - one below and one above your mid point.

And yes, don't forget to knock off your VR / IS when using a tripod.

To be honest i completely forgot about that. At the time i thought i was shooting down 2 stops and up one stop; i forgot they were done in thirds.

Do you think it's a good or bad idea to be changing the aperture for each shot, or should i just be changing the exposure time?

5uspect

gnolan wrote: »

Again, i wouldn't be familiar yet with tone-mapping - i assume i would do this in Photoshop? For the shots i took last night, would i get decent results by changing the exposure in post processing to give more of a contrast between the images?

Tone mapping is basically just messing about with the intensity of various parts of the image(s) histogram to get an image with out any dark shadows or over bright highlights. When you go through the HDR wizard in PS you have to export the constructed 32bit image into viewable format. This is where you tone map the data and PS offers a few different way to do this. Other applications like Photomatix or what ever it's called can be more sophisticated, if of course you think HDR is sophisticated :pac:.

gnolan wrote: »

One more question about this. When i open the RAW in Photoshop, will it not cease to be a RAW file and become a PSD? When editing each individual RAW in Photoshop, do i perform my edits and just save as .NEF? Will i lose any significant amount of data in doing this?

When you open and edit a RAW file you are making zero changes to it.
If you look at your file browser you will see that PS creates a additional file that contains details about the edits you've performed. All these edits are just reductions and permutations of the data in the RAW file. It is never edited nor AFAIK can you save to RAW. Think of a RAW as a digital negative. You can reprocess it in different ways but you cannot edit the negative.

You can convert the propitiatory format NEF or CR2 files from your camera to a DNG file also. This is sometimes needed when new cameras aren't supported by older versions of PS.

When you want an output file to print/upload/whatever you have to save that particular edit as a portable format like TIFF or JPEG.

gnolan

By the looks of it PS saves the RAW changes to an .xmp file. I have changed some exposure values around in the 5 images i took last night, i also changed the tone in all of them which had been set to "Shade".

My problem now is when i go to merge the files, Photoshop merges the original RAWs without the changes i made. Do i have to save each RAW i edited as TIFF/JPEG and then merge?

5uspect

When you merge to HDR you're using the raw RAW files. Any additional processing you're doing such as contrast cropping etc will have to be done after in PS.

Alternatively you could save 16bit versions TIFFs of your processed RAWs first and HDR them. You'll have to edit the workflow options in CameraRAW.

gnolan

5uspect wrote: »

Alternatively you could save 16bit versions TIFFs of your processed RAWs first and HDR them. You'll have to edit the workflow options in CameraRAW.

I think i'll do that, i'll want to change around the levels in each RAW file considering i didn't really shoot them correctly. Thanks for the help.

5uspect

Simply changing the levels won't help. You cannot just add information that isn't there.
Your selection of images need to capture the full dynamic range of the scene.

gnolan

5uspect wrote: »

Simply changing the levels won't help. You cannot just add information that isn't there.
Your selection of images need to capture the full dynamic range of the scene.

As above my range of shots covers only over 1 stop. My idea was to leave the reference image as it is, lower the exposure on the two darker images by 0.5EV and raise the exposure on the two lighter images by 0.5EV. I know it's not ideal because i messed up the exposure of my original shots, but would this not suffice in a makeshift sort of way?

5uspect

gnolan wrote: »

As above my range of shots covers only over 1 stop. My idea was to leave the reference image as it is, lower the exposure on the two darker images by 0.5EV and raise the exposure on the two lighter images by 0.5EV. I know it's not ideal because i messed up the exposure of my original shots, but would this not suffice in a makeshift sort of way?

If your scene has more dynamic range than your camera can capture in one scene then the histogram is missing information. You will not be able to record the blackest shadows or the brightest highlights. (The sun silhouetting something for example). Your eye tricks you by darting around the scene constantly adjusting exposure so you can see a lot more detail than a single exposure.

In order to capture the full dynamic range you need to take images of each part of the light distribution of the scene separately. A longish exposure for the really dark areas, a really quick exposure for the bright areas and several in between.

You can then numerically determine the correct distribution for the scene based on the relative exposure of each image. The more overlap and the more images you have the better the scene is measured and the better the signal to noise ratio.

If you don't have images that cover the full dynamic range of your scene you cannot add that information unless you get the paint and clone brushes out. You can make the image look HDRish by simply messing about with curve adjustments.

You're only shifting the data or removing information by adjusting the levels of the image. If you darken/lighten the image you shift the histogram left/right and risk clipping shadow/highlight data. It looks different to you but you've only added a constant to your data, there is no new information.

gnolan

Ok, thanks for that. The images i took don't cover the full dynamic range. Next time i'm out what approach should i take?

For example, maybe level the light meter at 15 seconds for the reference shot, and then shoot two at 10sec and 5sec, and two at 20sec and 25sec? Since i've been reading up on it i've seen many conflicting ideas on changing the aperture and exposure time.

5uspect

Your camera no doubt has an auto exposure bracketing feature that will queue up over and under exposed shots. Then look at the in camera histogram to see if you're covering the light. Repeat this as necessary.

Also why do you want to do HDR? Would you better off blending a few exposures or using grad filters?

Edit: Why do you need 25 second exposures? What were you photographing?

gnolan

5uspect wrote: »

Your camera no doubt has an auto exposure bracketing feature that will queue up over and under exposed shots. Then look at the in camera histogram to see if you're covering the light. Repeat this as necessary.

Also why do you want to do HDR? Would you better off blending a few exposures or using grad filters?

Edit: Why do you need 25 second exposures? What were you photographing?

It was a nighttime shot and i was looking to get in some headlight and brakelight lines on the image.

Unfortunately my camera doesn't support AEB, but i've only just learned that my light meter displays measures from -2 to +2 EV - still learning the basics.

Why HDR? I don't know really. Seems much more straight forward - although you wouldn't know it from my posts! I don't think a grad filter would have been suitable for what i was shooting - i imagine they'd be better for horizon lines and clearly delineated areas of contrast? I don't really know anything about blending exposures; i thought that was pretty much what HDR was.

5uspect

gnolan wrote: »

It was a nighttime shot and i was looking to get in some headlight and brakelight lines on the image.

Unfortunately my camera doesn't support AEB, but i've only just learned that my light meter displays measures from -2 to +2 EV - still learning the basics.

Why HDR? I don't know really. Seems much more straight forward - although you wouldn't know it from my posts! I don't think a grad filter would have been suitable for what i was shooting - i imagine they'd be better for horizon lines and clearly delineated areas of contrast? I don't really know anything about blending exposures; i thought that was pretty much what HDR was.

This is the problem with a lot of new photographers. They think HDR is the technical pinnacle of photography but have no idea why and when to use it. HDR is in fact an overused technique that often leads to awful over processed images.

If you're shooting car light trails I don't see the need to use HDR. These shots are all about the contrast of the streams of light against a dark background. This light will always be extremely bright and possibly over exposed. If you want to achieve the effect of light trails on a seemingly day lit road I would say your better off blending layers in PS.

So instead of numerically computing the correct high dynamic range and all that technical stuff you simply take two or more images in PS, layer them up and use layer masks to hide bits and pieces to build a composite image.

The screen blend mode is ideal for blending blacks.

gnolan

5uspect wrote: »

This is the problem with a lot of new photographers. They think HDR is the technical pinnacle of photography but have no idea why and when to use it. HDR is in fact an overused technique that often leads to awful over processed images.

If you're shooting car light trails I don't see the need to use HDR. These shots are all about the contrast of the streams of light against a dark background. This light will always be extremely bright and possibly over exposed. If you want to achieve the effect of light trails on a seemingly day lit road I would say your better off blending layers in PS.

So instead of numerically computing the correct high dynamic range and all that technical stuff you simply take two or more images in PS, layer them up and use layer masks to hide bits and pieces to build a composite image.

The screen blend mode is ideal for blending blacks.

I wasn't using the HDR for the light trails, i was using a long exposure time for the light trails. The reason i was using HDR was because the roads and buildings were very well lit and the sky was particularly dark that night.

To be honest it was just an experiment to see what different things the camera was capable of, and what Photoshop was capable of. But i think HDR suits the situation.

5uspect

Well experimenting is where a lot of the fun is!

If the sky is dark just use an upside down grad.

gnolan

5uspect wrote: »

Well experimenting is where a lot of the fun is!

If the sky is dark just use an upside down grad.

It was sort of a case where the sky was taking up all of the background of the image, there were trees, a bridge and other obstructions. In fact, i posted the photo in the random pictures thread. You can kind of see where i didn't get all the detail in the sky because i only took shots covering 1 stop.

Out of interest, what situations would you deem suitable for HDR?

5uspect

gnolan wrote: »

It was sort of a case where the sky was taking up all of the background of the image, there were trees, a bridge and other obstructions. In fact, i posted the photo in the random pictures thread. You can kind of see where i didn't get all the detail in the sky because i only took shots covering 1 stop.

Out of interest, what situations would you deem suitable for HDR?

Well here is one of mine:


I would consider it a good technique when the regions can't be easily tackled with a filter but I would try to avoid the heavy handed tone mapping.

CabanSail

gnolan wrote: »

Out of interest, what situations would you deem suitable for HDR?

Many would answer "None. It's the spawn of Satan and should be banished to a place where no eye can behold of it's visage of evil"

Then some would say "There is not a shot which cannot be improved upon with the glories which lie in the domain of HDR" but they are yet to mature or are quite delusional.

The way I see it is that it's a technique which can be worthwhile in some rare circumstances. This is where the information required in an image exceeds the dynamic range of your sensor. The hard bit is to recognise these situations and then to apply the HDR in a way that it is in keeping with the image you are trying to make. IMHO the best HDR shots are those where you cannot tell it's been used. See the thread in the main forum started by Actungbarry about his salvation from a severe HDR addiction.

gnolan

It'll take me some time to get used to situations where its use is merited - and even longer, i imagine, to get used to being able to properly process the images; tone curves seem particularly important, and i can't seem to get to grips with them whatsoever.

I'll leave it there anyway, thanks for the input, particularly 5uspect.

Rainbowsend

I dont know what part of the country you are in, but there is a free HDR photoshoot in Dublin Castle on the 15th of this month at 5pm. The Institute of Photography are running a masterclass beforehand for €45 if you are interested.