Natural Light with Focus Beam enabled only...

Hi all;

I was just wondering as a general question to all the photogs out there. How many of you use your higher end flashes with the flash disabled and assist beam on only?

The reason I ask is that I find, in low light, sometimes when having to push to ISO 1600 or above, if I don't use that feature, even my best lenses with my 5D Mk IV (with 700-200 Mark II, 85 prime, 24-70 Mark II, etc.), the focus get's missed at full open, or slightly stopped down (2.8, 4). This seems to be a recurring issue when using available light that waxes and wanes while indoors (clouds passing over, etc.) or even outdoors if the subject is far enough.

It seems the only remedy sometimes it to just take multiple shots, but sometimes that "key shot" happens very quickly and does get missed, or a not "as sharp" as it could have been.

Aside from enabling the Assist beam on the flash, are their other techniques under these situations to increase probability of a clear shot, I'm very conscious of not recomposing (too much at least) after locking focus and ensuring I fire right away.

Anyway, and additional input is appreciated.

Thanks!

A lighter weight solution was Canon's own old ST-E2. Both a 5DIII & 7D were helped considerably by its AF assist pattern. It's the reason I hung on to my ST-E2.

(BTW, the Yn clone was OK in some respects, but nowhere near as helpful wrt AF assist.)

Hmmm, interesting...like my 7DII the 5DIV brightness range for AF goes as dim as -3EV light. I have to stand in that dim light for 10-20 minutes before I can even see what is in front of me! And I have confirmed that AF does work at that dim level (although I tested only with center AF point, and not with some of the others)

The cell phone LED helps my focus many times, and is always available.

That's actually a neat workaround.

It seems (so far at least) that there is a general consensus, that the low light where ISO is pushed does challenge spot on AF. The reason I am kind of getting obsessed about this is because what ends up happening is that I rely on a "shotgun algorithm" where I take many shots of the same pose and one or more look good--this can sometimes end up with my favorite shot being spot on or way out--which kind of sucks.

Is this kind of non-deterministic, or is it recognizing that AF (while it can lock at -3EV as @Wilt said) does have limitations with natural light that isn't always at it's best.

I know a a lot of the photos we see on here are the best of the best of a session from any given photog, but maybe we can get a dialog going here where we can go back and forth, posting some samples of when AF is dead on and when AF is a little, or a lot out of focus, where we though it should be? I'd be interested to follow this concept to ground, to see what techniques, either outside the camera, or using the camera features themselves can help in these situations.

I'll dig around for some samples of my own. In the mean time, if you guys have some sequences that show AF drifting and what was done to compensate would be great!

Thanks for the help so far guys/ladies...I appreciate the interest in my little OCD problem

Thanks,
Tom

I would be VERY disappointed if my brand new 5DIV was having trouble focusing at 1600 level light.

That said, the focus system has a bunch of options and human failure is potentially more likely than camera error. Have you used DPP to see which focus point was active on the missed focus shots? Are you using a subset of focus points? Cross point only?

Thanks for the response LHB,

I have to say it's been a problem from time to time. I don't think it's the hardware. If that were the case I wouldn't need to start this thread. I'm sure it is a technique issue here and there. That being said, I am pretty conscious of my focus points when using such shallow DOF. I will often use single point or single with 4 Assist (more the single though). I did disable the all non cross points at one time, but believe I re-enabled them. I haven't used DPP, but the camera does provide an option to see which point was used, but that's during the shoot itself and non while processing, so maybe DPP would be a good idea.

Having said that, I don't think this is a unique issue for my situation, which is why I asked for maybe some samples (I should probably start that with my own before asking others). The samples with a narrative as to what was done to correct a mistake in technique is kind of how I was thinking to solve this problem. It's not a terrible problem by the way, it's just something that can be annoying, especially on critical shoots (weddings, etc.) As an insurance policy I will often stay away from wide open and come down to about 5.6 which minimizes almost completely, missed shots, but also requires pushing ISO, or pushing exposure in PP...which BTW I am reading is sometimes a preferred method by some with the outstanding dynamic range of the 5D Mk IV...shooting under to get better speed at lower ISO and pushing 1-2 stops in PP resulting in same IQ...I've tried this and have been surprised at how good the results actually were. Anyway, that's another topic for debate. For now I'd rather shoot with proper exposure and use the apertures I paid so much money for while getting the best predictability from 1 shot to the next...

This whole idea might be a foregone conclusion as its possible I just need to go back to basics and follow some strict guidelines for these shooting environments (No external flashes, natural light only, shallow DOF, sometimes very high ISO). But I do feel like I am being conscious of the "gotchas" with this and looking for some pointers. Your DPP idea is a good one!

Thanks,
Tom

Just bumping to see if anyone else wants to weight in...would like to know what other people do and if they have similar experiences...

Thanks all
Tom

tfitz wrote in post #18572305
Having said that, I don't think this is a unique issue for my situation,

i think it probably is more unique to you than you want to believe. Depending on SS and aperture, I'm not even sure the focus beam would be visible at some 1600 level shots. I shoot my 6D at 3200 and 6400 (1/200 f/3.5) center point (which should be what you have with lots of your cross points) with zero problem focusing.

um, yeah.

help us, help you.

Yonguno YN-622 for me, light weight, resonably good IR pattern, also if you need to add a speedlight to it, there's the pass thru hotshoe built in.
Used this setup for years during Wedding first dance's....

Thanks for the reply LHB!

I'm a little confused about what you said about the AF Beam and the SS and aperture? From what I understand, the AF processing (I think), goes something like this:

1. Select AF, and points.
2. Point camera and press half way down (for instance)...at this point the Aperture is wide open (in my case let's say 2.8 on the 70-100)
3. The AF Assist beam from the 600 EXII-RT is illuminated onto the subject (in the case of the 600, all of the points are supported I believe so it always turns on, or at least on most of the points). Again, Aperture still wide open
4. There are two AF sensors (or dual arrays--it's been quite awhile lol) where each one is slightly offset creating a phase difference if the image is not in focus.
5. Probably using some kind of PID loop, the AF processing stream commands the lens to adjust until the phase difference is as minimal as possible (in focus)
6. At this point the photo is considered in focus and the focus light turns on in the viewfinder and I would then press completely down on the shutter button.

It would be at this point my Aperture setting comes into play,because now the camera closes the Aperture down to the setting I have it (or the setting it chose if Shutter Pri.) The camera then fires and this is where the SS would come into play.

So I guess I don't understand how the AF Beam is related to SS and firing Aperture? Also in 1600 ISO conditions wouldn't this imply that the ambient light is somewhat darker than lower ISO's. If this is the case it would result in a more prominent AF pattern relative to the ambient light, so the higher the ISO, the better the pattern would appear for AF lock.

Maybe I have something turned on it's head, but I think that's how it would flow.

Anyway I liked your idea about DPP and comparing the focus. I haven't tried it yet but I will

I just finished a shoot a couple of weeks ago and I kept some basic "wide aperture" rules in mind and kept those fundamentals in my mind the whole time...the most dominating factor I seem to be finding is to ensure your Z-axis delta is as low as possible from the time your finger moves to the time that shutter fires. It's an easy thing to forget because sometimes the AF point is not dead on where you need it to be and you end up recomposing. At 2.8 or lower, that alone can alter the AF, but during that time not only can the sensor plane move along the Z-axis because I move slightly, but so can the subject (face, head, whatever), I found the best shots were when I did not re-compose at all and fired immediately at those apertures, If I had enough light I would go down to 4.0 or 5.6 and then had more wiggle room.

But again, there could be some additional fundamentals I am missing, or always have been that result in soft images here and there.

ISO 1600, f/16, 1/1600 shutter would be proper exposure in full daylight, according to sunny 16

Equivelant to the above in different conditions:
f/11 Slight overcast
f/8 Overcast
f/5.6 Heavy overcast
f/4 Open shade/sunset

You've already said you do not need to use flash.

In open shade, the AF beams are not going to be a shining beacon of AF light on your subject.