Alright This is going to sound weird but I don't see any difference between HDR and bloom.

I run at 1600 something resolution on a 22" monitor. I can tell a huge difference when not on this rez but that's because most monitors display better at their native resolution, AkA their max.

I run Qarls.

High resolution body textures.

and about 100 other mods as well.

At that res AA doesn't do much, other than lower my FPS, but what is the difference between HDR and Bloom?

I ask this because I'm at work and it is possible I have changed options in areas that might not reflect the true differences.

Can anyone thuroughly explain the differences between these two lightings?

Bloom kinda makes everyone look like they have a lighter outline, atleast for me, and seems to be lower performance. HDR, with standard settings tends to look a bit over exposed, making a walk through the IC on a bright day, a blinding experience.

The real difference is that HDR can be tweaked and adjusted to whatever will work best with your videocard, while bloom doesn't seem to have many options for tweaking the look of things. Bloom however does seem to work better with shadows and water reflections.

Atleast from what I've noticed. Probably wrong on all accounts, have a fairly old videocard installed.

Can't really define them but I can say that using HDR makes everything seem sharper, more realistic, less drab. I didn't care too much for Bloom.

I had to run Oblivion with HDR off for a while due to the Black Screen problem, but got some expert help from the author of the UOP (also UOMP & USIP).

Running Oblivion without HDR enabled was a drab experience, to say the least.

the difference is that you need to buy a new card... thats all its there for... thx god oblivion was usable without it unlike some other games by bioware and 2k...
if you ask me the whole hdr and bloom idea is horrible... it was ok for vice city since you got that irie coke feeling but for somin like oblivion... lol... well its ok but not necessary imo...

The differance between bloom and HDR can be hard to see when not directly compared. To see the difference in Oblivion between HDR, bloom and none of them take a look at the screnshoots in the Oblivion Tweakguide at tweakguides.com

http://www.tweakguides.com/Oblivion_7.html

The screnshoot with bloom enabled is brighter than the screenshot with none of the effects. The screenshot with HDR is brighter and has warmer colours than the screenshot with bloom

HDR does several things, but the easiest to notice is therse:
With HDR there can be greater contrasts betwen dark and illuminated surfaces . This makes light sources and illuminated of surfaces brighter (bright things can be really bright, dark things can be really dark) , I think bloom also does this to some extent, but not as well as HDR.

HDR also simulates the way the human eye adapts to changed light conditions. When looking at something bright the eye adapts so it after a moment looks a bit darker. This is not the case with bloom.

Since FearlessHamster said almost everything to be said about the issue I'll try append just a few tech details.
At some extent both are similar and try to sharpen contrast. But while HDR is dynamic (so the name) and need special hardware, bloom is much more flexible in this (would be much more slow than HDR if this last wasn't so resource hungry).
Another thing is bloom acts in the whole scene while HDR tends to be more specific drive to particular points.
But if Oblivion is the only to be weight in the answer another issues comes hard: HDR in Oblivion doesn't allows using Anti Aliasing and so get the contour less smooth if one VC can afford AA and anisotropic filtering (edit: this last is the resposible for those little shining in the objects that bloom and HDR just amplifies, HDR having something in its own here too).

So using HDR, bloom or none is more a question of compromise in oblivion. Even the HDR use isn't optimized here and lead to astonishing views at some places thru eyes harming ones in others (I got bored to death with HDR and at minor extent bloom every time I entered conversation with NPCs).

This is a thread that can't be answered with objectivity, the better choice is the one that fit better your taste or runs more smooth.

PS edit: My personal taste is bloom with some AA and anisotropic filtering, tweaking a bit with the contrast and brightness so to minimize the max the "face to face" conversation and general over exposition... to better this I use the mod that zoom out these "encounters". Anyway HDR is sure the best to take panoramic screenshots

Before someone asks, the "zoom" mod is named something as Talk with your hands" if I correctly recall.

antisoptric filtering = shining on objects? mmmh actually its more the perspective correction of textures making em sharper
the shining come from normal maps... turn af off and theyll still shine...
or maybe i misunderstand somin lol

No, you are right, I meant Specular distance and messed all things
I'd love to say was the late hours to blame... no, this will not work

Modern graphics drivers for either nVidia or Ati can do AA and hdr... for oblivion at least. Somehow I haven't gotten the two to work in eve online yet .

My explanation of hdr: Every texture in the game gets an extra set of 3 textures (in greyscale)... one for high light, one for low light and one for low light. Through a complicated set of algorithmns that I don't really understand these extra greyscale textures tell your gpu how reflective the object is. Most obviously is that the shiney rocks just look awesome. Metal looks like real metal due to the way it shines... and the world looks more fantasy (cartoony isn't right word) and realistic at the same time. It adds a great deal to immersion and is definitely worth the $200 for a new 8800gt/4850. It's kind of like anistropic filtering... it just adds all that extra detail into the textures making for a lot more immersive experience. It also makes the colours look a lot richer too.

I really enjoyed the blare and stuff you get in the city from the light shining off of the white stone buildings.

The tweakguides example is pretty good though. If diablo 3 doesn't support hdr I'll be might pissed off.

I'm not exactly sure why, but on older graphics cards HDR can look even worse than Bloom, even though the card can use HDR. I used HDR for a while until I got tired of having my eyes submitted to something equal to the sun everytime I walk around and look at walls in the IC or look at somebody's face while they are facing the direction of a light source.