Controlling ISO with Canon 5d

[TonyW]

I recently bought a Canon 5d mark III with the standard kit lens (24-105). I am not a very experienced photographer and so I have been confronted with a steep learning curve but I think I am making reasonable progress.

For most of the photographs, I have been using the P mode with single point spot focus, which seems suitable for what I have been doing. I can still adjust the balance between shutter speed and aperture. The automatic choice seems to lean towards the maximum aperture. Perhaps the algorithm thinks that because I am using spot focus I don't mind having a small depth of field but there are times when I do. It also seems to choose the minimum ISO speed that it thinks it can get away with, which leaves little room to manoeuvre. This seems unnecessary since the ISO speed can be reasonably high before there is any problem with noise.

My question is: How can I adjust the ISO speed to make it higher in these conditions? It is possible to set a minimum ISO speed which would probably do the job but this seems a bit too complicated if I want to vary it from one shot to another. Is there some better strategy which would do everything I need?

[Cantab]

Tony, I have a Canon 60D and don't know to what it extent it differs from the 5D so I won't make suggestions that might simply confuse them matter.

Hopefully someone with a 5D will answer your question. If not, I'll give you my advice based on the 60D in the future.

[patrick9x9]

Hi Tony, I have the 5D III also although I admit I've never used P mode. I shoot full manual. So I thought I'd pick up my camera and see how the P works. When I set it on P, I can still set the ISO, and I choose the aperture. I can go from 4 to 22 on my 24-105. By the way I'm pretty sure that is the 24-105mm L lens which by no means is considered a kit lens. You may have bought it together as a kit, but it is a profession L series lens. Great lens. Anyway, I digress. So in P mode you can choose the ISO and the aperture and the camera picks the shutter speed you need. So as you look through the camera, you just turn the main dial and that is changing the aperture and the camera is changing the shutter speed accordingly based on your aperture and ISO. Sorry, I'm not really technically up with everything about it. Does that help at all?

[patrick9x9]

Sorry, I should have mentioned if you want a deep dof, meaning most of your picture in focus use a high f-stop, probably around f16. I should have explained the 4 to 22 I was referring to is f-stop or aperture. The lower the number (f-4) the narrower your dof will be (less in focus). Also it depends on what your shooting, I only use spot focus if I'm shooting through or around things or trying to focus on just an eye of an animal. I do mostly landscape so for me the more focus points the better.

[Ken MT]

From page 127 of your manual it appears that you have the ISO set to auto. I suggest that you set it to manual ISO (say 400)
then the camera will not automatically change the ISO on you. With Program it appears that the widest aperture is used, then the ISO is changed to make the shutter speed the reciprocal of the focal length of the lens. eg 1/50 sec at 50 mm, 1/100 sec at mm etc

[dje]

Hi Tony and welcome.

I think Ken has answered your question - it does sound like you have ISO set to Auto. With Auto ISO, as the exposure is reduced, the lowest ISO setting is used until the exposure is such that a certain minimum shutter speed is reached (which is able to be set on the 5D III I believe). As exposure is reduced after this, ISO will be increased to maintain that minimum shutter speed until you reach the max ISO setting (which you set). After that, shutter speed will start reducing again as exposure is reduced. There is no minimum ISO setting in Auto ISO mode as far as I'm aware.

There are some circumstances where Auto ISO is useful but in general, I prefer to use a fixed ISO setting. It is very quick to change it using the ISO button.

I don't use P mode. I suppose it mostly does all you want but I prefer to use Av, Tv or full Manual. I use Av a lot more than Tv as it is usually the DOF ( and hence aperture) that is the starting point for me. I suggest you try all these modes to get a feel for them.

Dave

[TonyW]

Thanks for all the replies - they have been most helpful. It looks as though the M mode would be the most appropriate solution for me but as Dave suggests I should try all of them. Time and experience will tell me which one is most appropriate. Most of the my shots so far have been of people, birds and other animals so the spot focus is good and I most often do not have the luxury of time because birds and animals do not stand still and it is important to catch the moment with people.

I am going travelling in a couple of days so my typical usage might change.

My next questions are going to be about lenses. On my wish list are a macro lens, for which the 100mm F2.8L seems to be the one, and a telephoto lens which is a harder choice. I need it for birds, among other things.

By the way, Dave, I am also in Brisbane. I must update my personal information.

Tony

[dje]

By the way, Dave, I am also in Brisbane. I must update my personal information.

Tony

That's good to hear Tony.

Dave

[jcuknz]

I think by choosing M you are taking a giant leap towards chaos Much better would be to set the ISO to 400 ISO and use A mode when if you want depth of field then pick the larger number. My aperture is usually at f/5.6 or f/8 most of the time. The danger in using A mode is that in less than bright light the camera will pick a slow shutter speed leading to subject blurr and camera shake by yourself. So you need to monitor what the camera is choosing when you take half trigger as you set-up/consider the shot. I hope the manual mentions half trigger somewhere.
I think you would find that A mode is very popular and used by newbies through to experts and they only go to M mode when they know that the automatics and A mode is not going to give them the result they want. I shoot MFT with an instant one second playback following taking the shot in the viewfinder which I don't think DSLRs do, certainly my old 60D doesn't. It is a very quick and useful confirmation I have got the shot I was hoping to take before going on to the next shot.

[rpcrowe]

When shooting in Programmed Exposure Mode, I always choose my ISO manually. That is one of the advantages of the P mode over the fully Automatic mode. However, I would think that using Auto ISO along with Programmed exposure would be somewhat confusing and difficult.

I think that using auto ISO is best when shooting in manual exposure. That way, you select the two parameters (shutter speed and aperture) that you believe will provide the best imagery and the camera will select the ISO.

The 7D was the first of the Canon DSLR cameras to have fully functioning Auto ISO; so I would assume that the 5Diii also has this capability. Here is a rundown on using auto ISO with manual exposure on the 7D. I guess that the 5Diii would operate in a similar fashion...

http://www.dpreview.com/articles/020...for-canon-slrs

The latest firmware update for the 7D allows you to select a maximum ISO to be used in the Auto ISO mode. I don't know if a firmware upgrade is required for this in the 5Diii or if the camera's original firmware allows maximum ISO selection...

BTW: IMO, one of the best venues for auto ISO and manual exposure is in sports photography when I want to achieve and maintain a high shutter speed as well as a specific aperture for max DOF or a for more narrow DOF when using selective focus.

[Ken MT]

The Canon 5D Mk 2 also has auto ISO available, but does not have selectable limits, eg goes from 100-3200 with all modes excluding B and M, and for M,B and flash it is fixed at 400, unless fill flash results in overexposure when a lower ISO will be used.

[William W]

I recently bought a Canon 5d mark III with the standard kit lens (24-105). . . For most of the photographs, I have been using the P mode with single point spot focus . . . I can still adjust the balance between shutter speed and aperture. The automatic choice seems to lean towards the maximum aperture. Perhaps the algorithm thinks that because I am using spot focus I don't mind having a small depth of field but there are times when I do. It also seems to choose the minimum ISO speed that it thinks it can get away with, which leaves little room to manoeuvre. This seems unnecessary since the ISO speed can be reasonably high before there is any problem with noise.

There appears not a lot of DETAILED technical information on the ALGORITHM of P Mode – but in my study including detailed testing and analysis of P Mode in EOS Cameras – I have never noticed the functionality to be linked to the AF Point Selection.

P Mode will APPEAR in many shooting scenarios, somewhat biased to selecting a (faster) shutter speed and that sometimes will take into account the FL of the lens. Certainly the 24 to 105 would communicate to the 5DMkII relevant information in this regard.

The 24 to 105 is not a fast lens (Maximum Aperture), so P Mode might seem not to select any other aperture than F/4 – but it doesn’t work that way. P Mode will, depending upon conditions select other apertures when you are using that lens.

Considering that is seems you had AUTO ISO selected and that AUTO ISO functionality will strive to keep the ISO lower rather than higher, therefore when the two functionalities “talk to each other”, once the Shutter Speed is happy, it would be reasonable to assume the ISO is selected to the lowest possible – hence the Aperture seems always to be at F/4 or thereabout.

***

My question is: How can I adjust the ISO speed to make it higher in these conditions? It is possible to set a minimum ISO speed which would probably do the job but this seems a bit too complicated if I want to vary it from one shot to another. Is there some better strategy which would do everything I need?

You might have missed the point that you can USER SELECT the high and low LIMITS for AUTO ISO. See P 127 of your user manual.

***

Thanks for all the replies . . . It looks as though the M mode would be the most appropriate solution for me but as Dave suggests I should try all of them.

Noted that you will try all the Camera modes – but – I suggest that M Mode might not necessarily be the most appropriate selection for you.

As well as trying (learning) all the Camera Modes – I suggest that you try (learn) the Metering Modes: FIRST.

In any of the AUTOMATIC Camera Modes (Av Tv and P) the Camera’s TTL Light Meter will make the first selection of exposure – that one fact is usually, (IMO should be), the predicate for choosing one of the Automatic Camera Modes INSTEAD OF M Mode.

*

Expanding on the point of ISO Selection:

As mentioned you can USER SELECT the LIMITS for Auto ISO.

Also you can manually set the ISO to suit the range of the shooting scenario you expect.
For example – if you are taking family photos outside on a sunny day at a park then you can reasonably expect to take picture in full front lit sunlight (as the brightest scene) and under the dark shade of a big tree (as the darkest scene).

That would be (about) EV 15 to EV 9.

You could manually set an ISO to accommodate that EV range and also still have enough shutter speed across the range to arrest (most) Subject Movement. For example set ISO400.

In full front-lit sunlight (EV 15) you would be pulling: F/16 @ 1/400s @ ISO400 (or the equivalent that P Mode selects for you).

At EV 9 you would be pulling: F/4 @ 1/100s @ ISO400 (and this is likely the exact selection that P mode would make for you.)

However in the example above: AUTO ISO could be selected to limit at ISO100 and ISO800 and that IMO would be a more elegant solution, if one chose to use P Mode in the first inst..


***

My next questions are going to be about lenses. On my wish list are a macro lens, for which the 100mm F2.8L seems to be the one, and a telephoto lens which is a harder choice. I need it for birds, among other things.

The lenses you choose and advice as to which are better should be predicated on what you intend to shoot – the descriptions are a tad short on detail.

For example – what macro subjects?
For example - what birds? – In flight? From an hide? Hand Held?
For example – what’s the budget?

Those points stated, the EF 100F/2.8 L IS Macro is an excellent lens. Suitable for most general macro work on a 5D series and will provide an adequate working distance for most general macro and close up subjects and situations. I’d advise buying the Tripod Mount Ring (and a tripod and or a monopod) if you really want to explore Macro.

On Birds – the EF 400F/5.6L USM is a well priced value for money lens used by many bird enthusiasts.

HOWEVER, I’d advise that Lenses and Lens acquisition should be thought of in terms of how they fit into the “WHOLE KIT” in terms of the Photographer's requirements and usage as well each lens's individual use and specificity.

For example: the 25 to 105 has quite a reasonable close up capacity (which is noted as “Macro” in yellow on the focus turret of the Lens).

That close up capacity may be (or may not be) all that you require at FL = 100mm. So, in terms of working distance, a 50mm or (65mm) or 180mm Macro Lens might be better for you. (Lenses mentioned were limited only the Canon offerings).

WW

[inkista]

Just me, but if you want to set the aperture and the ISO and have them stick, then maybe it's time to move out of P mode and into Av (aperture priority) and non-Auto ISO. That way, whatever ISO you want to set will stick, whatever aperture you want to use to control the DoF will stick, and the camera will automatically set your shutter speed for you, based on the metering, and then you can adjust from there.

If you were in M mode, the iso and aperture would stick, but camera will just give you the meter reading, and all setting of the shutter speed is up to you, too.

One more thing, you said:

...with single point spot focus,

Just out of curiosity, are you sure you're talking about focus here (where you only have a single AF point active vs. the entire grid), or are you talking about the spot metering mode (vs. averaged and center-weighted)? Because spot metering definitely affects how the camera sets your iso/aperture/shutter speed.

[William W]

One more thing, you said:

...with single point spot focus,

Just out of curiosity, are you sure you're talking about focus here (where you only have a single AF point active vs. the entire grid), or are you talking about the spot metering mode (vs. averaged and center-weighted)? Because spot metering definitely affects how the camera sets your iso/aperture/shutter speed.

+1
Good pick up.

I missed that: and maybe relevant. Does have an affect P Mode computation - definitely.

WW