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12-01-2018, 11:01 PM   #1
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AF540FGZ II distance in wireless

I have been using a AF540FGZ II flash on my K3 for a year only mounting on the camera. I use it only to shoot family and friends photos. I am still a very beginning learner. I now want to use the flash off camera. When I take it off camera in wireless mode, I don't see the distance scale on either P-TTL or M modes. Can someone explain to me how to find the right distance for the flash when used wireless?

12-02-2018, 02:55 AM   #2
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Hi, the Range and distance indications are only displayed during on-camera operation (P-TTL, or M modes) .... This is because the calculation needs the aperture and ISO information sent from the camera, and this is only transmitted through the hotshoe.

Also the indications do not work when the flash head is in a bounce configuration.

You can do the maths yourself, or refer to the histogram for exposure adjustments as needed. Really distance should be more about the quality of light , not the intensity.....power should be adjusted to get the desired flash exposure once your distance is established. The indications are useful as a guide should you be at the limits of possible distances, allowing adjustments in advance to correct

Last edited by mcgregni; 12-02-2018 at 03:01 AM.
12-02-2018, 07:46 PM   #3
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I agree with McGregni in his reply. I used to use wireless all the time until I bought my K3-II and was no longer able to control a single flash (no built in flash). I usually turned my 540 down a few notches and that was the only setting I changed until the exposure was right. As for the distance, it's hard to say. I would ask someone else to confirm if the flash went off as it wouldn't all the time. It needs a clear line of sight to work and I usually twisted the body of the flash so that it was facing the camera while the actual flash was facing the subject. Indoors I found no limits as to range as long as nothing blocked it. Outdoors I would set it up at a campsite and there too I found it reached as far as I wanted it to reach. Basically it worked pretty well except that occasionally it just wouldn't work.
12-02-2018, 10:06 PM   #4
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Thank you very much for clearing it for me that the range and distance indications cannot be transmitted when the flash is in wireless mode. It would help me if there was a possibility of entering the ISO and aperture on the flash itself to get the distance indication. Is it only by trial and error that I will find out what the distance, power level and zoom of the flash that I need to use? Being busy with work, I get very few photo taking opportunities of my family. It might take very long for me to learn by trail and error. I found that in extreme lighting conditions like shooting into the sun or against the backdrop of dark skies, the P-TTL gives wrong exposures where I need. That is why I wanted to do it manually and was looking for some sure fire ways of getting correct exposures before getting creative with off camera flash. Are there any ways to quickly learn to get correct exposures with wireless flash?
QuoteOriginally posted by mcgregni Quote
Hi, the Range and distance indications are only displayed during on-camera operation (P-TTL, or M modes) .... This is because the calculation needs the aperture and ISO information sent from the camera, and this is only transmitted through the hotshoe.

Also the indications do not work when the flash head is in a bounce configuration.

You can do the maths yourself, or refer to the histogram for exposure adjustments as needed. Really distance should be more about the quality of light , not the intensity.....power should be adjusted to get the desired flash exposure once your distance is established. The indications are useful as a guide should you be at the limits of possible distances, allowing adjustments in advance to correct


12-03-2018, 09:08 AM   #5
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You would probably enjoy using the older 'Mk1' model of the AF-540FGZ ..... its 'A' mode uses an on-flash sensor to quench the output, plus you input the ISO and apertures directly onto the flash. This allows it to display the "range" available even when off-camera (because it doesn't need any camera to flash communication to measure the correct output). But its not a fixed distance, as you get with Manual mode, its a range like for P-TTL, which shows you the nearest and furthest distance that it will be able to provide good illumination.


Now, maths is not my forte ...(I'm lucky I only really got going with flash in the digital era!) .... but I'm sure some more mathematically able members will give you some formulas to quickly work out your power levels in Manual mode (come on people!), lets help him out here.


One thing you can do is to set up your flash on the camera in manual mode, and then dial in on the camera a typical aperture and ISO you often use, then set the power level to 1/1 and read off the distance indicated ..... then go through all the power steps and make up a table or chart listing all the power steps with the distance readout written alongside. You could make up a few different charts for each typical set of aperture and ISO combinations (eg F2.8 / ISO100), F5.6 / ISO200, F4 / ISO 800 etc) .... all the ones you are likely to use when shooting off camera flash.


Then when setting up the flash as a slave you simply check your charts and read off the power level required for the distance that your flash is placed from the subject. Bear in mind these distance indications relate only to bare flash ... if using modifiers like softboxes or umbrellas then you have to factor in additional power, eg 1 or 1.5 extra stops of power depending on your diffuser.
12-03-2018, 12:41 PM   #6
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QuoteOriginally posted by mcgregni Quote
some more mathematically able members will give you some formulas
How about the guide number tables in the AF540FGZii user guide? Those, along with the guide number exposure formula (below) should provide an indication of maximum P-TTL range for a given zoom setting as well as manual mode calculation.
F-number = GN/distance

distance = GN/F-number
Of course, the lazy way is to visualize the distances that work with on-camera usage and trust that P-TTL will also work well for those same flash-to-subject distances when controlled remotely. Chimp and adjust the flash EC up or down as needed. FWIW, maximum distance for P-TTL with zoom set to 58mm is about 10 meters at f/5.6 and ISO 100 shrinking to about 5.5 meters at the 16mm setting. These numbers shrink significantly if bounce flash or light modifiers are used.

While I have used P-TTL off-camera, my preference anymore is to go full manual and chimp a lot.

BTW...I second the recommendation of the AF540FGZ with its "Auto" feature for that kind of set-up.

Resources:
Understanding Camera Flash Guide Numbers, plus GN Calculator (Don't be put off by the dated appearance, this page has a lot of information.

Strobist

Steve

Last edited by stevebrot; 12-03-2018 at 01:25 PM.
12-03-2018, 01:19 PM   #7
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A few more simple things related to the flash exposure triangle (distance, guide number, EV):
  • Increase the EV two stops (aperture and/or ISO) allows one to double the distance
  • Doubling the guide number translates to two stops less EV
  • If exposure is proper at 2 meters, extending the distance to 4 meters requires one EV more exposure. Similarly for 5.6, 8, 11, 16, and 22 meters.

    If the sequence of numbers above looks familiar, it is because it the same as for aperture stops.


Steve

12-03-2018, 01:25 PM   #8
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QuoteOriginally posted by stevebrot Quote
...
distance = GN/F-number
...
Shouldn't that equation be

distance = [GN/F-number] [sqrt{(actual ISO)/100}]

?
12-03-2018, 02:03 PM   #9
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I quite liked it when he wrote "chimp" ....


But as always some really good structured explanations from Steve, thanks.


I get the impression that most people using multiple off camera flashes nowadays, tend to have gained a personal "feeling" for their particular flashes / strobes and use an instinctive approach to initial manual power settings. For example, at home I work in a small space with my Main light (softbox), fill Light (umbrella) and hair light (bare) very close to the subject (eg 1 to 2 meters away for each light). My three flashes are all similar GN, so for F8 at ISO200 I have just leaned from experience to start with my Main light (softbox) at 1/4 ..... the Fill (umbrella, a bit further away) also at 1/4 .... and the hair light, a bit further away again, at 1/16.


These are repeatable and memorable for each time I use a similar setup, and inevitably lead to only minimal, maybe a half stop, adjustments.


So when I move to a bigger space or outdoors, I still use these remembered starting settings, but mentally adjust for any extra distance (I suppose subconsciously using the formulas and patterns that Steve detailed above). But ultimately we have the huge benefit of the histogram to assess test shots, and I do this with each light individually, and adjust to place each light exactly on the histogram where I want it ..... eg main light about 75%, fill about 30%, hair about 60%.

Last edited by mcgregni; 12-03-2018 at 02:40 PM.
12-03-2018, 03:21 PM   #10
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QuoteOriginally posted by kaseki Quote
Shouldn't that equation be

distance = [GN/F-number] [sqrt{(actual ISO)/100}]

?
Yep!

Guide numbers are always ISO dependent so that term is not needed for illustration purposes, though your point is well taken. In practical terms I would generally convert the guide number to the working ISO before doing any calculation.*

I suppose there is an omnibus phone app that is useful for all those chores.

(I would have provided a reference to a flash calculator app, but I don't use one.)


Steve

* ...or adjust the F-number up or down to suit.
12-03-2018, 03:32 PM   #11
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Thanks Mcgregni and Steve for helping me out. I think at the moment flash off camera in manual is kind of mystery to me. I will try to use the Steve's formula (or is it Kaseki's?) and actually take some photos and evaluate and slowly go up from there. My guess is, with some practice I should get a hang of it all. I may have to beg my family to be patient with me till then

The problem I have with the histogram when I use P-TTL with extreme ambient light like looking into sunset or darker skies, the flash does not expose my subject well but the histogram looks OK. Maybe, I need to practice more and learn to read the histogram better. I am hoping that going fully manual I will get more consistent results that I want.

I will look at phone apps that might help me get what I am missing with the absence of "A-mode" on my flash.

I have started reading on Strobist. There is a lot to learn but it should be exciting and rewarding.

Thank you all for being of so much help.
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