ISO 50 - when to use it?

[chris_shawn]

Hello,

 

another simple question: In what kind of situations would you use ISO 50.

Probably: tripod, a lot of light, etc. But does it make the photos look better?

Can you really spot the difference? Does anyone have an example picture or know

of a site with a comparison between ISO set to 50 and 100? Is it suitable for

portraiture with studio flash light?

 

Thanks!

[remco-jan.woldhuis]

Assuming you shoot digital: The lower the ISO value, the less signal amplification is

needed which means you end up with less noise. Theoretically the photos should look

better.

[CharlesBecker-Toronto]

back in my film days, I went on a tour to China; I shot Kodachrome 25 rated at 32 and a friend shot Kodachrome 64. Most days were overcast and I had to shoot at slow speeds-my friend used to joke about asking everyone to keep motionless while I was taking the picture. At the end of the trip when we were back home, we had a slide show and compared images and there was no question that the Kodachrome 25 was 'superior'in every way . I love my Nikon D-70 but the lowest ISO setting is 200 which I regret but my digital lenses are slower than my old lenses so perhaps it's just as well. Use the lowest ISO setting that will do the job-it does make a difference. cb

[m_barbu1]

Actually, from what I understand, neither ISO 50, nor ISO 3200 are true ISO values on the EOS digital cameras. They are both achieved by "adjusting levels", so you'll likely get better results from ISO 100. I would thus extrapolate that you should only use the L and H ISOs when absolutely necessary, and avoid them at other times. This would explain why Canon has "segregated" them into custom functions. I guess they want to make sure you really know what you're doing, so you don't use it and blame them for poor results.

[ethan_adler]

The last poster is correct.

 

You would want to use ISO 50 with a lot of light and you want to have a wide open aperture for shallow depth of field to seperate your subject from the background.

 

I have had to take an outdoor portrait and the light was so bright that even with the highest shutter speed a wide open aperture I was getting saturation. If I could dial up the ISO (I didn't have ISO 50 at the time), I could have kept the wide open aperture.

[colin carron]

Chris, on the 1DS Mk II and the 5D the native ISO range of the sensor is 100-1600. There is also an L setting of 50 and H setting of 3200 which can be set in the menus. The reason they are set separately is that the native ISO range is a function of the sensor and the H and L settings are derived from software manipulations of 100 and 1600 speed images.

 

So you are probably not going to gain anything from setting L or H which 100 or 1600 would have got you except if that speed gives you a particular lens aperture or shutter speed.

[mark u]

If you use ISO 50 on a Canon DSLR you have a risk of blowing out highlights - so it should only be used where you need to eek detail out of shadows, and where highlights are not going to be a problem.

[steve_dunn2]

<p>But remember that you lose some dynamic range at ISO 50. From what I've been told, the sensor can't actually do 50; the shot is metered at 50, shot at 100 (which results in a one-stop overexposure), and then digitally pulled down a stop; the loss of dynamic range is from how +1 tends to blow highlights. This is kinda like how 3200 is done, but in reverse; the sensor can't do 3200, so the shot is metered at 3200, exposed at 1600 (which results in a one-stop underexposure), and then digitally pushed a stop.</p>

 

<p>So unless there's a reason you simply cannot shoot at 100, you're probably better to use 100 than 50 for most scenes.</p>

[marknagel]

I actually use it a lot (5D). For my indoor portrait work, I will meter the strobes to ISO200 at f/5.6, then to lower my DOF I will swap to ISO50 at f/2.8. Much faster than adjusting the power of 4 strobes each time.

 

I did do several comparisons ISO 50 vs ISO 100. I scrutinized and could see no difference.

 

Mark

[mendel_leisk]

Chris, why not just try it? Eliminate as many variables as possible: manually meter, set up on a tripod, shoot when the sun is not likely to go behind a cloud or whatever.

 

Dynamic range is supposedly reduced, so shoot situations where that's likely to show.

 

Create a 'test' folder, dump your test shots in there. Take notes. Open your comparison shots in Photoshop, view overall, view zoomed in.

 

Draw your conclusions: any reduction in noise? Are highlights blowing sooner?

[Spearhead]

<i>If you use ISO 50 on a Canon DSLR you have a risk of blowing out highlights </i><p>

 

If the shot is correctly exposed, highlight issues will be the same regardless of the ISO. This statement is wrong and should have read "If you use ISO 50 you may not be able to expose correctly in bright light (although most DSLRs have high enough shutter speeds to handle most bright situations) and that could risk blowing out highlights." That is completely different than the ISO itself causing problems.

[miles_hecker]

Never...

[robin_sibson1]

Wouldn't a ND filter be a better solution?

[mark u]

I believe Jeff is incorrect. The cameras operate as Steve Dunn indicates, with the result that a correct exposure at 100 ISO will capture the maximum achievable dynamic range - the brightest pixels will use the full well capacity. Switch to ISO 50 and double the exposure time, and the highlights will be blown because the pixels cannot record all the photons that hit them without overflow, but the shadows will be less noisy unless the exposure is of very long duration such that thermal sensor noise intrudes. Switching to ISO 50 and maintaining the same exposure as at ISO 100 will fill the pixels as for a 100 ISO exposure, but there will be some loss of IQ as the capture is pushed in post processing.

[eric merrill]

Jeff:

 

"If the shot is correctly exposed, highlight issues will be the same regardless of the ISO."

 

That's not my experience with the 5D.

 

If you use equivalent exposures, you have a greater chance of blowing the highlights on ISO 50 than on any other ISO setting on my version of the 5D. When I first starting using it, I assumed that lower ISO = better. Just like film. That's an incorrect assumption.

 

 

Eric

[kahkityoong]

N Barbu's response is correct. However I use it when I need to use a slower shutter speed

than what ISO 100 allows e.g. waterfalls, eddies.

[William Michael]

This really interests me, technically, it is an area I have been researching over the past few months. For those interested and adding weight to much of what has been written:

 

From original documents [Canon] the following seems to be correct:

 

ISO 50 and 3200 are not true [digital] ISO values within the ISO parameters interpreted by the camera`s ISO software, but `produced` by [additional] software.

 

This [additional] software manipulation is NOT simply using ISO 100 or ISO 1600 and `adjusting` the aperture / shutter speed [i.e. exposure] by one stop, other parameters are also modified, it seems including, but not limited to: photon acceptance rate, photon overflow rate and the noise parameter although it has been difficult obtaing documents to verify directly.

 

This additional software manipulation does not, however, produce a practical result that would be expected, in that: there not the [continuance] of the defined [expected mathematical] relationship between differing ISO settings. That is to say, between ISO 100 to ISO 50 and between ISO 1600 to ISO 3200 we do not have the [same / similar] progression we get as we move through ISO 100 to ISO 1600.

 

In the practical world, these present with many results some of which include: blown highlights or less [than expected] contrast at ISO50 and more [than expected] noise at ISO 3200 and poorer [than expected] image quality at both ISO 50 and ISO 3200.

 

(Blown Highlights at ISO50 explained above, - Photon Overflow)

 

Having performed another exercise it is worthwhile mentioning.

 

In similar practical experiments, it seems [in many situations] that setting, for example ISO 200, metering the scene and shooting in Manual Mode at the prescribed metered setting and comparing this image to the same scene under same conditions and same aperture and shutter speed at ISO 100 and ISO 400, but shot with Exposure Compensation ONE STOP OVER or ONE STOP UNDER respectively, renders differing images in terms of quality [especially contrast, noise, edge acutance: 100% enlargement view on a corrected screen at 15 inches].

 

I extrapolate that the Exposure Compensation and ISO parameters work in discrete, or only partially intersecting, sets.

 

This research came about as I was investigating the use of ISO 50 or `L` setting prior to a purchase.

 

In summary I find the `H` or 3200 setting more practically useful than `L` or ISO 50, I use the `H` setting on my 20D often, from what I have found [theoretically and practically] I do not think I will use the `L` function often, should I purchase a 5D or other body which offers this option. A `genuine ISO 50 would however be another issue, but I can not see R & D going this route.

 

As mentioned a ND filter would be the go, rather than ISO 50, if necessary.

 

Regards WW

 

To Mr Nagel:

>I actually use it a lot (5D). For my indoor portrait work, I will meter the strobes to ISO200 at f/5.6, then to lower my DOF I will swap to ISO50 at f/2.8. Much faster than adjusting the power of 4 strobes each time.<

 

I am really interested in how we arrived at different results, my assumption is that using strobes [in a studio setting, perhaps lighting people / skin tones] your overall EV Range, (perhaps about 3 to 4 stops?), was smaller than my testing, which was done outdoors in Sunlight on a range of inanimate subjects varying widely in reflectance and colour; my test scenes also included black as black shadow.

 

Your application and point noted, it seems a good one for ISO 50.