More 50D Questions

Richard

I finally broke down and ordered a 50D. I should get it on Monday, but in the meantime I have been looking at the manual. Do highlight tone priority and auto lighting optimizer affect RAW files? What are they useful for and what problems can they create?

ziggy53

Richard wrote:

I finally broke down and ordered a 50D. I should get it on Monday, but in the meantime I have been looking at the manual. Do highlight tone priority and auto lighting optimizer affect RAW files? What are they useful for and what problems can they create?

I have not used the "Auto Lighting Optimizer" function yet. The "Highlight Tone Priority" (HTP) I use quite a lot and it does help to keep detail in the highlights. It does seem to function in RAW files as well.

It has been speculated that HTP is a curve type tonal adjustment during the imaging chip to amplifier phase of image acquisition. That would mean that after the chip images the scene and the imager pre-amplifiers do their thing, HTP interjects a tonal adjustment before the main amplifier (or perhaps during the amplifier phase) but before the image processor phase. Unfortunately Canon is not saying exactly what is happening and when it happens.

You do lose ISO 100 (and I believe the very highest ISOs as well) and there is a bit more shadow noise as a result of HTP, but it is not the same as simply using ISO 200 and a minus EV adjustment to protect the highlights, as some have suggested.

BTW, I don't have a Canon 50D but I use HTP on the 40D and 5D MKII. I believe that they all work the same way.

Gringriff

ziggy53 wrote:

The "Highlight Tone Priority" (HTP) I use quite a lot and it does help to keep detail in the highlights. It does seem to function in RAW files as well.

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You do lose ISO 100 (and I believe the very highest ISOs as well) and there is a bit more shadow noise as a result of HTP, but it is not the same as simply using ISO 200 and a minus EV adjustment to protect the highlights, as some have suggested.

Ziggy,
You mention that you lose some ISO settings which makes me wonder if this HTP setting works best when using flash or not or does it matter? I have not used it.

I have played around a little with light optimizer on the 50D but I can not yet quantify what the effects are.

Andy

eoren1

Richard wrote:

I finally broke down and ordered a 50D. I should get it on Monday, but in the meantime I have been looking at the manual. Do highlight tone priority and auto lighting optimizer affect RAW files? What are they useful for and what problems can they create?

Hey Richard,
I'm pretty sure that Auto Lighting Optimizer is JPG-only and thus I have it turned off on my 50D
The Highlight Tone Priority is a different beast. I researched this a bit when I got my camera and just read some more after seeing your post. Basically, the HTP does affect RAW (you effectively lose ISO 100 and 3200+). However, the effect is very dependent on how you process your RAW files. With DPP, the camera provides a tone curve to add to the processing 'recipe'. However, with ACR/LR, the program only sees an effective exposure compensation of -1. Because of this, you end up with the potential for more shadow noise when using that function. I have it turned off on mine.
Hope that helps,
E

ziggy53

Gringriff wrote:

Ziggy,
You mention that you lose some ISO settings which makes me wonder if this HTP setting works best when using flash or not or does it matter? I have not used it.

I have played around a little with light optimizer on the 50D but I can not yet quantify what the effects are.

Andy

I've tried the HTP mode in ambient and flash environments and I like the benefits.

ziggy53

eoren1 wrote:

Hey Richard,
I'm pretty sure that Auto Lighting Optimizer is JPG-only and thus I have it turned off on my 50D
The Highlight Tone Priority is a different beast. I researched this a bit when I got my camera and just read some more after seeing your post. Basically, the HTP does affect RAW (you effectively lose ISO 100 and 3200+). However, the effect is very dependent on how you process your RAW files. With DPP, the camera provides a tone curve to add to the processing 'recipe'. However, with ACR/LR, the program only sees an effective exposure compensation of -1. Because of this, you end up with the potential for more shadow noise when using that function. I have it turned off on mine.
Hope that helps,
E

True, in ACR you generally have to bring up the exposure and that destroys the highlights "except" that I use a tone curve in ACR to protect the highlights and I do believe that I see a benefit of more detail in the most extreme highlights versus no HTP.

Here is the approximate curve:

Richard

50D Auto-ISO
Thanks for the information, everyone. I now have the new toy and am starting to learn my way around its features. First impressions are very good, compared to my old 20D.

OK, here´s another question: How well does auto-ISO perform for you? I couldn´t find any explanation of the algorithm on the Web, and I find it a little disconcerting that the camera does not let you specify the thresholds that you want to trigger an ISO change. OTOH, I did see a claim that the camera takes focal length into account when it computes the minimum shutter before raising ISO, which seems fairly smart. I also saw several posts that claimed the 50D implementation of auto-ISO was much better than the 40D´s.

So--does anyone use auto-ISO? Why or why not?

dlplumer

Richard wrote:

Thanks for the information, everyone. I now have the new toy and am starting to learn my way around its features. First impressions are very good, compared to my old 20D.

OK, here´s another question: How well does auto-ISO perform for you? I couldn´t find any explanation of the algorithm on the Web, and I find it a little disconcerting that the camera does not let you specify the thresholds that you want to trigger an ISO change. OTOH, I did see a claim that the camera takes focal length into account when it computes the minimum shutter before raising ISO, which seems fairly smart. I also saw several posts that claimed the 50D implementation of auto-ISO was much better than the 40D´s.

So--does anyone use auto-ISO? Why or why not?

I would much rather set my own ISO, and it is so fast and easy on the 50D. This months POP photog. says one should never use auto ISO. To me, setting ISO, shutter speed and aperture are how you control the quality of each shot. JMHO.

Art Scott

Richard wrote:

So--does anyone use auto-ISO? Why or why not?

Nope......it is a control thingy......I want control...........

eoren1

Richard wrote:

Thanks for the information, everyone. I now have the new toy and am starting to learn my way around its features. First impressions are very good, compared to my old 20D.

OK, here´s another question: How well does auto-ISO perform for you? I couldn´t find any explanation of the algorithm on the Web, and I find it a little disconcerting that the camera does not let you specify the thresholds that you want to trigger an ISO change. OTOH, I did see a claim that the camera takes focal length into account when it computes the minimum shutter before raising ISO, which seems fairly smart. I also saw several posts that claimed the 50D implementation of auto-ISO was much better than the 40D´s.

So--does anyone use auto-ISO? Why or why not?

The problem with the 50D's ISO is it is quite stupid... it looks for the minimum ISO that will allow a reasonable shutter speed. I was finding that it would typically go for speeds of 1/50th second which just did not work for low light shots of moving toddlers. The ease of changing settings (compared to my prior 350D) made this a non-starter and I have not used the autoISO function since.
E

Richard

Yeah, I understand the advantage of control. OTOH, I have ruined a number of shots on my 20D because I have forgotten all about checking the ISO when starting up a session. I realize that´s my own fault, but protecting me from my own stupidity doesn´t seem like a bad thing. Happily, the ISO is finally in viewfinder, so maybe that´s enough.

My first experiments with auto ISO would seem to indicate that the camera is doing pretty much what I would be doing manually--in Av mode, it selects the lowest ISO that keeps the shutter speed from dropping below the reciprocal of the focal length. I don´t have enough experience to say how well it performs in borderline cases. One concern is that it uses fractional ISO settings, which some people claim introduces more noise. I don´t know yet how much of a problem that will be for me...I´m not a pixel peeper, but I don´t like noise any more than the next guy. We´ll see.

Richard

eoren1 wrote:

The problem with the 50D's ISO is it is quite stupid... it looks for the minimum ISO that will allow a reasonable shutter speed. I was finding that it would typically go for speeds of 1/50th second which just did not work for low light shots of moving toddlers. The ease of changing settings (compared to my prior 350D) made this a non-starter and I have not used the autoISO function since.
E

Right, point taken. That´s a good example of why it would be better to let the photographer set the thresholds.

pilotdave

Richard wrote:

So--does anyone use auto-ISO? Why or why not?

I find myself using auto-ISO most of the time now, unless I want to bump the ISO up to get faster shutter speeds or smaller aperture. In my use of the 50D, I often have it mounted where I can't adjust the controls... on top of my head. And lighting conditions can change drastically in seconds. Auto-ISO has been very helpful. But, it doesn't work the way I'd like it to. Usually I'd prefer to bump up the ISO in favor of shutter speed, so i wish i could tell it to start at 200 or 400.





Dave

Gringriff

Richard wrote:

So--does anyone use auto-ISO? Why or why not?

I will not use it for my shots but sometimes I will take a quick shot with it on to see what the camera would use or to get my white balance set using the card. Once that is determined I may use it as a baseline and then go into M or AV mode and set the ISO based on conditions and the other settings I use.