Red flame-out

I took a shot of a bright red Dahlia this week (K50 with DA18-135) and when I checked the image it seemed as if the red was 'blown out'

I know people say that it is difficult to shoot white objects but is it a common problem also with bright reds.

I spent some time working on the RAW image and managed a partial recovery but wondered what other people have to say ?

First here is the camera jpeg followed by the result from working on the RAW file in PSE11, all comments welcomed :-

they look pretty good to me.
but i'm no expert.

Bright reds are the colours most easily prone to burning out, particularly on flowers, like Dahlias and Poppies. Your recovered shot looks pretty good to me though.

As a rule I will generally shoot at least one full stop under-exposed for red flowers and sometimes even less exposure than this to avoid any possibility of burn-out. Another flower colour prone to this is bright yellow, e.g. plants like buttercups.

Regards
David

The lighting is also a major consideration. For flower shots I prefer bright overcast to sun as it reduces the contrast and avoids blocked up shadows.

Yes, red can be tricky, but the light can work against us as well.

Hi, I would have taken with a lower shutter speed and thus lower ISO. Red does seem to over saturate more easily.

The one I posted recently of a very bright red crocosmia was taken with 2.3 negative EV and even that almost failed to avoid blow out.

I've read advice saying its a good idea to activate the colour channel histograms on the camera LCD as this gives a more accurate picture of highlight blow -out ... You get one for each of RGB. I usually only use the plain brightness histogram, but this red flower scenario would seem to be the ideal time to use the red channel histogram.

I'd use this and still try for an 'optimsed' exposure (ie 'ETTR where possible) .... The danger of a general underexposure (eg1stop) approach is that if the contrast is quite high then pulling down your mid-point EV too much will cause any background in shadow to almost go black .... This produces an often seen stylised effect which can be used as just that ...an effect .... But I much prefer the natural look with nice soft greenery in behind as you have here Peter.

Davids point above about using -2.3 ev has to be seen in a metering context .... That amount of minus ev suggests that the metering was mainly averaged and included a good amount of non-highlight information. In most cases, using a targeted metering area on the brightest parts would normally involve an INCREASE in exposure value to get the best IQ (ie an ETTR approach) ....

However, could it be something about the colour red that seems to deceive the meter system somewhat?

Tell me about it... I've spent ages this "summer" trying in post -production, to tone down blown-out reds and, to an equal extent, yellows, without affecting the rest of the image. I can't remember slides and prints from negatives suffering from the same thing. I've not found an answer but generally have accepted that these colours will blow slightly even at best and hope that it's not too noticeable.
It's actually easier in a shot such as yours where you don't have to worry about keeping other colours bright. The picture below of Mrs C. at Cothele certainly doesn't bear close inspection...

Many thanks to all of you for the useful comments.

It was only after I'd posted this question that I checked the EXIF data and saw the 1250 ISO, so I did wonder if that might be part of the problem.

The reason the camera selected this high ISO was that I was using 1/500 on f/8 on TAv as it was fairly windy, so I wanted the fast shutter speed !
I now realise that I should have lowered the speed a bit and also opened the aperture a bit ?
Still, one only learns from one's mistakes !

Thanks again
Peter

In theory of course Peter, ISO shouldn't really have any varying or inconsistent effect on exposure value, all else being equal. The suggestion made here seems to be that higher isos would cause more blow-out on reds .....

I would have thought with a modern camera like yours that 1250 is fairly modest and I'd question whether it would have any significant impact ... ?

The lowest isos do offer improved contrast and depth (ie better blacks) and perhaps it is this aspect, plus perhaps a dynamic range boost as well (?) that means red exposure is better at low isos ... ?

The key is probably correct metering. If this was the full frame, then the background isn't excessively bright, but the flower is brighter so overall the exposure just might benefit from -0.3 to -0.7 EV adjustment, assuming the use of centre-weighted metering. This would hold back the red from being over-exposed.

Spot metering would be an alternative, but only for those who really understand it, as its use with auto exposure modes can lead to some erratic metering results.

I always avoid matrix matering patterns as we have to double-guess what the camera algorithms are designed to do, so applying some intelligent adjustment to that becomes more difficult.

Doing that will not alter the overall exposure, it will stay the same. So any over-exposure will also stay the same. You need to deviate from the indicated exposure, so that means using minus amounts of exposure compensation if in an auto mode. If in manual, it means under exposing compared to the indicated zero point.

Red and yellow are two colours that extend well beyond the gamut of our monitor displays. So they can't be displayed other than looking burnt out.

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As long as the red value doesn't exceed something just under 255 then it won't look washed out, all that happens is that colours outside the gamut can't be shown.

Yes, I agree with all of that John ...I feel that drawing high iso into it is complicating the matter, which as you say is really about metering technique and choices.

Personally, I came to SLR photography relatively recently (:wink and have generally stuck with the matrix patterned choice. Certainly I have not found that inconsistencies with this cause any concerns, and I think it does not take much experience with a particular camera to gain that sense of it needed to quickly make compensations.

I've tested sometimes and for many scenes there is no difference in EV produced between multi-pattern and centre-weighted modes.

I'm not sure if this is posted as a good or bad example? Certainly to me on my monitor a lot of the detail looks out of gamut. There's a lot of detail in the petals not visible in colour.

Very quick conversion to B&W



There are many tutorials on the web for working spaces. This is just one....

http://www.cambridgeincolour.com/tutorials/sRGB-AdobeRGB1998.htm

Note reds are mostly outside the sRGB and AdobeRGB1998 colour spaces.

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