Flash and auto ISO

[BeBu Lamar]

I think you're a decade late to that rant, Stuart. I've upgraded my dSLRs three times during the time I've had some film sitting in the fridge waiting for me to feel it was worth the expense of getting it developed.

 

 

 

There is no "minimum ISO" to the best of my knowledge. In auto-ISO, the ISO always varies between the (native) camera base ISO and the set maximum. The set maximum is whichever is higher of the explicitly set ISO and the auto-ISO "Maximum sensitivity". I see the same behaviour whether I set ISO 64 and maximum sensitivity 6400, or maximum sensitivity 80 (you can't set 64) and manually set ISO to 6400. I now do the latter - I have to remember to change ISO when I switch to manual ISO, but at least I don't need to dive into a menu to change the upper limit for auto-ISO.

 

Pointing out of the window with a 50mm lens, apparently it's sunny outside. I just checked again, and P mode selects ISO 6400 (my set upper limit), 1/6400s, f/16.

 

...ah. Okay. So the user-selected ISO is used to choose other parameters in P, S and A, and the camera will increase it if need be, if and only if the auto-ISO sensitivity maximum is higher. In manual mode, you get the ISO needed to match the other two parameters, and both explicit ISO and auto-ISO set only the upper limit - they're interchangeable. If explicit ISO is set to something between the camera minimum and the explicit sensitivity limit, it's ignored in manual mode. I normally shoot with M, so I'd missed the distinction. (I'd have met it if I shot aperture priority, but util Nikon give us a fast way to shift the shutter speed limit/auto-shift without going into a menu, it's limiting.)

 

I probably switched to using ISO the way I do for manual mode relatively recently, recently enough not to realise the interaction. In which case, the "auto ISO limit/native ISO independence" slide on the Nikon requests should better have said "provide a better way to set maximum ISO in auto-ISO". I'd have said use the front and rear dials for the native and upper limits, but then you need another way to toggle auto-ISO on and off (perhaps push and release ISO without turning anything?)

 

I don't mind learning new things every day, I just don't like it when I'm learning old things that I've forgotten.

 

I still don't understand what you did. What is the range of ISO you allowed your camera to vary? My camera I set the low limit of ISO100 and high limit of ISO12800. When I pointed at a scene about the same brightness at yours it picks f/5.6, 1/125 and ISO100 just like what I expected.

[stuart_pratt]

I think you're a decade late to that rant, Stuart. I've upgraded my dSLRs three times during the time I've had some film sitting in the fridge waiting for me to feel it was worth the expense of getting it developed.

 

But a completely pointless argument might kill some time - Some of us have got plenty of that at the moment!

[rodeo_joe1]

But a completely pointless argument might kill some time -

Pointless? Absolutely!

But I'll let a couple of pictures make the main point:

The following image shows about 1/18th of the area of a T-max 100 negative, 'scanned' at in excess of 6000 ppi. Camera used was a Pentax Spotmatic F with 55mm f/1.8 Super-Takumar:

This next one was taken with a Canon Eos 5D (original 12Mp model). Same lens, same subject and distance, same exposure settings, same small crop:

 

The price of a 5D seems currently to be under £200. Whereas a good, working Spotmatic F will cost you around £70 + Film + developing equipment + chemicals. Say another £50 at least. About 10 or 12 films later you'll have broken even with the 5D, and you'll just keep getting further out-of-pocket from there onwards. With, as can be seen, inferior image quality, and a worsening environmental impact.

 

Oh, yes, nearly forgot. No scanning or enlarging equipment was taken into account in the above costing.

 

Case stated.

Edited May 8, 2020 by rodeo_joe|1

[stuart_pratt]

Pointless? Absolutely!

 

 

Case stated.

 

Touché Joe! ;)

 

[Andrew Garrard]

Touché Joe!

;)

 

Also that film will be trashed by sitting in the sun with the film exit pointing up. Unless the flocking is a lot better than I'd expect. At the point, most of the film in my fridge is doing an experiment to see how many cosmic rays hit the UK.

 

I still don't understand what you did. What is the range of ISO you allowed your camera to vary? My camera I set the low limit of ISO100 and high limit of ISO12800. When I pointed at a scene about the same brightness at yours it picks f/5.6, 1/125 and ISO100 just like what I expected.

 

If you shoot in manual mode with auto-ISO, there is no "low limit": the camera varies between its native lower limit (64 on a D810) and whichever is higher of the auto-ISO maximum sensitivity and the ISO value that you set. For example, if ISO is manually set to 400 and the auto-ISO maximum sensitivity is set to 3200, and I point my camera out of the window in daylight, it'll typically pick ISO 64. Exactly the same happens if I set the auto-ISO maximum sensitivity to 400 and the manual ISO to 3200 - or, more usefully, if I set the maximum sensitivity to 80 and the manual ISO to around 6400, where I tend to leave it.

 

Since I usually shoot in manual mode, this is why I was confused by the idea of "minimum ISO". The two are entirely interchangeable in manual mode, except that the minimum "maximum sensitivity" is ISO 80, and you can change the manual ISO setting without going into menus but have to enter menus to change the maximum sensitivity. Because the "maximum sensitivity" can't go down to 64 (presumably because an engineer wasn't thinking of it this way), you can't be in auto-ISO and just dial the ISO down to 64 if you really want the base value - you have to turn auto-ISO off as well. Having established that they're equivalent, I now typically shoot with "maximum sensitivity" set to ISO 80, because I can then dial the ISO limit without entering the menu - I'd typically stick to something moderate partly because above a certain point you're just throwing away highlight detail and not gaining any shadows, so you're better underexposing and fixing it in post. But since Nikon don't have an option to "push exposure" in the JPEG preview, if I do that I may not be able to see whether I've hit focus or got unreasonable motion blur - so I fiddle with settings. A down side is that my ISO is set very high if I turn off auto-ISO, and when I turn off auto-ISO it's usually because I want ISO 64.

 

(As an example of the push JPEG thing, yesterday I took some photos of the VE day street party outside my house. I exposed the image for the blue skies, because I don't like to blow them. I trust that I can recover the shaded foreground, but in the JPEG I can't see a thing, so I just have to hope.)

 

In other exposure modes, the camera starts at the ISO you manually selected and will increase the ISO up to the max ISO limit if it can't otherwise match the exposure parameters. The two aren't interchangeable.

 

I miss being able to put tables in the inline HTML, otherwise I'd be able to show this better. Let's try with bullets:

• Manual mode
  
  • Exposure within the range auto-ISO can adjust: auto-ISO adjusted for exposure with set aperture and shutter speed.
    
  • More light than a correct exposure at minimum ISO: overexposure (ISO 64/100).
    
  • Less light than the auto-ISO limit: underexposure (ISO at maximum of set ISO and maximum sensitivity).
    

  [*]Other modes

  • Exposure at the set ISO can be achieved by adjusting other parameters: ISO sticks to set value.
    
  • More light than can be handled with the set ISO: ISO drops to minimum (64/100), then overexposure.
    
  • Less light than can be handled with the set ISO: ISO rises to the maximum sensitivity, then overexposure.
    

That's slightly simplified - I assume actually P and A modes start extending the exposure time again up to 30s once the maximum sensitivity is needed. I've not shut myself in a cupboard to check.

 

I'd really like to be able to change the maximum ISO directly in all modes, and in aperture priority to be able to adjust the maximum shutter speed and maximum shutter speed auto shift. I don't really want to use manual exposure most of the time, it's just that variations in action require shutter speed tweaks and that takes too long in aperture priority. I did request the auto-shutter-limit-by-focal-length (on a D700, IIRC, auto-ISO in aperture priority is a pain if you've got a zoom), and Nikon implemented it afterwards (which gives me some hope that asking for things makes them happen, although I doubt I was alone), but it's still not quite ideal for me. It's certainly useful in specific settings, though.

 

On other occasions, I may have specific ideas about the order in which I'd like things to change, and the limits I'd like to place on them. I'd commonly like to keep shutter speed within an acceptable range (some motion blur, not too much), aperture in a range (acceptable lens aberrations, avoiding diffraction) and ISO in a range (bonus marks for allowing only 64 and 400, since the stop point of the amplifier means ISO 400 on a D850 seems to be worse than ISO 320). Then, if I know the kind of thing I'll be shooting and can set the camera up beforehand, I'd like to specify the order in which those rules would be broken, rather than leaving it to the exposure modes. 99% of the time this wouldn't be worth the effort, but 1% of the time I have the change to set up the camera but lighting during the sequence is highly variable - I come back to the "cheetah run where the cheetah runs between shadow and bright sunlight" situation.

[stuart_pratt]

;)

 

Also that film will be trashed by sitting in the sun with the film exit pointing up. Unless the flocking is a lot better than I'd expect.

 

 

 

LOMO?

[BeBu Lamar]

;)

 

Also that film will be trashed by sitting in the sun with the film exit pointing up. Unless the flocking is a lot better than I'd expect. At the point, most of the film in my fridge is doing an experiment to see how many cosmic rays hit the UK.

 

 

 

If you shoot in manual mode with auto-ISO, there is no "low limit": the camera varies between its native lower limit (64 on a D810) and whichever is higher of the auto-ISO maximum sensitivity and the ISO value that you set. For example, if ISO is manually set to 400 and the auto-ISO maximum sensitivity is set to 3200, and I point my camera out of the window in daylight, it'll typically pick ISO 64. Exactly the same happens if I set the auto-ISO maximum sensitivity to 400 and the manual ISO to 3200 - or, more usefully, if I set the maximum sensitivity to 80 and the manual ISO to around 6400, where I tend to leave it.

 

Since I usually shoot in manual mode, this is why I was confused by the idea of "minimum ISO". The two are entirely interchangeable in manual mode, except that the minimum "maximum sensitivity" is ISO 80, and you can change the manual ISO setting without going into menus but have to enter menus to change the maximum sensitivity. Because the "maximum sensitivity" can't go down to 64 (presumably because an engineer wasn't thinking of it this way), you can't be in auto-ISO and just dial the ISO down to 64 if you really want the base value - you have to turn auto-ISO off as well. Having established that they're equivalent, I now typically shoot with "maximum sensitivity" set to ISO 80, because I can then dial the ISO limit without entering the menu - I'd typically stick to something moderate partly because above a certain point you're just throwing away highlight detail and not gaining any shadows, so you're better underexposing and fixing it in post. But since Nikon don't have an option to "push exposure" in the JPEG preview, if I do that I may not be able to see whether I've hit focus or got unreasonable motion blur - so I fiddle with settings. A down side is that my ISO is set very high if I turn off auto-ISO, and when I turn off auto-ISO it's usually because I want ISO 64.

 

(As an example of the push JPEG thing, yesterday I took some photos of the VE day street party outside my house. I exposed the image for the blue skies, because I don't like to blow them. I trust that I can recover the shaded foreground, but in the JPEG I can't see a thing, so I just have to hope.)

 

In other exposure modes, the camera starts at the ISO you manually selected and will increase the ISO up to the max ISO limit if it can't otherwise match the exposure parameters. The two aren't interchangeable.

 

I miss being able to put tables in the inline HTML, otherwise I'd be able to show this better. Let's try with bullets:

• Manual mode
  
  • Exposure within the range auto-ISO can adjust: auto-ISO adjusted for exposure with set aperture and shutter speed.
    
  • More light than a correct exposure at minimum ISO: overexposure (ISO 64/100).
    
  • Less light than the auto-ISO limit: underexposure (ISO at maximum of set ISO and maximum sensitivity).
    

  [*]Other modes

  • Exposure at the set ISO can be achieved by adjusting other parameters: ISO sticks to set value.
    
  • More light than can be handled with the set ISO: ISO drops to minimum (64/100), then overexposure.
    
  • Less light than can be handled with the set ISO: ISO rises to the maximum sensitivity, then overexposure.
    

That's slightly simplified - I assume actually P and A modes start extending the exposure time again up to 30s once the maximum sensitivity is needed. I've not shut myself in a cupboard to check.

 

I'd really like to be able to change the maximum ISO directly in all modes, and in aperture priority to be able to adjust the maximum shutter speed and maximum shutter speed auto shift. I don't really want to use manual exposure most of the time, it's just that variations in action require shutter speed tweaks and that takes too long in aperture priority. I did request the auto-shutter-limit-by-focal-length (on a D700, IIRC, auto-ISO in aperture priority is a pain if you've got a zoom), and Nikon implemented it afterwards (which gives me some hope that asking for things makes them happen, although I doubt I was alone), but it's still not quite ideal for me. It's certainly useful in specific settings, though.

 

On other occasions, I may have specific ideas about the order in which I'd like things to change, and the limits I'd like to place on them. I'd commonly like to keep shutter speed within an acceptable range (some motion blur, not too much), aperture in a range (acceptable lens aberrations, avoiding diffraction) and ISO in a range (bonus marks for allowing only 64 and 400, since the stop point of the amplifier means ISO 400 on a D850 seems to be worse than ISO 320). Then, if I know the kind of thing I'll be shooting and can set the camera up beforehand, I'd like to specify the order in which those rules would be broken, rather than leaving it to the exposure modes. 99% of the time this wouldn't be worth the effort, but 1% of the time I have the change to set up the camera but lighting during the sequence is highly variable - I come back to the "cheetah run where the cheetah runs between shadow and bright sunlight" situation.

 

Oh so your D850 has 3 parameters in auto ISO. Min, max and set ISO. The Df only has min and max. The min is set on the ISO dial and max is set in menu. So the auto ISO of your camera really sucks. I never use auto ISO in manual. Manual is used when you use the EC or AE Lock. Since I do not use these features I use manual in those cases.

[BeBu Lamar]

But I still don't understand what you did Andrew? You have the set ISO st6400? That is 6400 is the priority 1 ISO to use? So no wonder it picked ISO64000. So it's because how you set it.

Now I don't care the minimum ISO whether is 64 or 80. I would want the priority 1 to be ISO 100 or so.

[Andrew Garrard]

Oh so your D850 has 3 parameters in auto ISO. Min, max and set ISO. The Df only has min and max. The min is set on the ISO dial and max is set in menu. So the auto ISO of your camera really sucks.

 

No, the D850/D810 only has the two parameters (its only difference for this discussion is the D850, but not D810, adds e4 "auto flash ISO sensitivity control" setting, and there's a separate "maximum ISO with flash" - but we've veered away from discussing flash). The parameters are just used differently in different exposure modes. Other than talking about the ISO dial on the Df (rather than being able to set the base ISO from the menu), the manual pages seem identical. Which also means, they lie, I think:

 

In exposure modes

P

and

A

, sensitivity will only be adjusted if underexposure would result at the shutter speed selected for

Minimum shutter speed

[...]

 

(Df, D810 and D850 manuals.) In a brief experiment with my D810, ISO is also adjusted below the explicitly-set shutter speed in aperture priority if I set f/1.8 and point out of a window - if I set ISO 400, the camera hits its 1/8000s limit, and starts dropping the ISO to ISO64 to hit the correct exposure. Obviously as the manual states, ISO increases if needed as well. The Df also just has "ISO sensitivity" and "Maximum sensitivity" - not an explicit "minimum" - I think it'll do the same here.

 

I suspect in manual mode with auto-ISO turned on, the Df will act like my D8x0 bodies: it'll pick whatever ISO it wants for correct exposure between base ISO (100 on the Df) and treat whichever of the menu "Maximum sensitivity" value or the setting on the ISO dial is higher as the upper limit for auto-ISO - meaning that, like the D8x0 bodies, there's a quick way to change the upper limit so long as you're in manual mode. I'm not an enormous fan of how clearly Nikon hasn't documented this. :-)

 

If there's actually a behavioural difference between the bodies, I'll be interested to know. Were I to try to "improve" it on the D8x0, I'd have a way to set the base and max ISO separately (probably front and rear dials with ISO held down), use a press-and-release of the ISO button on its own to toggle auto-ISO, and store everything separately by exposure mode (at least optionally). Given the chance at the Df, I'd have a menu option to choose whether the ISO dial was setting the base ISO or maximum sensitivity. I think that would be less confusing. But that's just me.

 

I never use auto ISO in manual. Manual is used when you use the EC or AE Lock. Since I do not use these features I use manual in those cases.

 

Ah, I may turn auto-ISO off for AE lock, since I'm usually in manual anyway. (Currently I can do that directly with the ISO button and the front dial; on the Df you either need to enter a menu or program the Fn or Pv button for that change.) Of course, because I'm using the ISO to set my upper ISO limit it manual mode, I also then need to set the ISO to something sensible, which is a little annoying but still faster than menu spelunking. I use the EC to dial the meter, which adjusts the auto-ISO chosen value in manual mode (or I use EC with auto-ISO turned off to spot meter on highlights).

 

But I still don't understand what you did Andrew? You have the set ISO st6400? That is 6400 is the priority 1 ISO to use? So no wonder it picked ISO64000. So it's because how you set it.

 

:-) Yes, it turns out that in the auto exposure modes, it did what I told it to do. I think your confusion about how manual + auto-ISO works is matched my my confusion about how the other exposure modes interact with auto-ISO; I figured they'd be more equivalent than they are. So in Program/Aperture/possibly shutter priority, the camera will choose the ISO I asked for if it can adjust the other parameters to make it happen, then change between base ISO and the set ISO sensitivity limit. In manual exposure mode (with auto-ISO) the camera will always adjust the ISO between base ISO and the upper of the ISO set and the ISO sensitivity limit, because it can't adjust anything else. What it doesn't do is start overexposing if the base ISO and ISO sensitivity limit are both set high.

 

Now I don't care the minimum ISO whether is 64 or 80. I would want the priority 1 to be ISO 100 or so.

 

Yup, on the Df, base ISO is 100 - you wouldn't want the camera to go below that, because all it would be doing is exposing at 1/100s and throwing some shadow detail away when it recorded the file. On the D810 and D850 (and Z7), the base ISO is 64 - you genuinely get a little more dynamic range than at ISO 100. You wouldn't want it to drop to ISO 32 for the same reason you wouldn't want the Df to drop to ISO 50 ("Lo 1").