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05-01-2022, 03:51 AM   #1
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About my new external flash...

Hey guys, I bought myself the Godox TT600 and it works just fine, I like it no complaint at all but I quickly realised that things would not go as I foreseen them to. In short, yesterday I took a few shots for the first time with it and my Godox XPro trigger and - it took me no time to understand this - since the integrayed flash was not popped out, the camera ( K-70 ) considered it as not active ( even if I set it to Always on ) and then raised the sensitivity to 1 200, which gave me an incredibly overexposed photo. My brother paid me a visit for pictures so I took them with no flash and it gave me surprisingly good results for the moment. But I really want to use my external flash beacause with the proper settings on camera results are going to be even way better. Now, the downside of it and the one thing I did not expect at first, I now know that I will have to use my camera in manual mode if I want to have full control of the shooting conditions. You can set the ISO even in auto mode but it will have effects on other settings...

So, I come to you this time to ask if you could recommend me a good tutorial about the manual mode, the way to calculate aperture, sensitivity, shutter speed an power level of the external flash. Thanks in advance once again for your precious help, hype.

05-01-2022, 05:11 AM   #2
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First of all does the XPro P trigger fire the flash gun remotely. The flashgun needs to be in slave mode and the channel and group needs to be the same on both units. Test fire the trigger before fitting it to the camera. This will establish that they are talking to each other. If they are then fit the trigger to the camera and take a test shot. I'm sure the camera manual will tell you how to use external flash.
05-01-2022, 06:11 AM - 1 Like   #3
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QuoteOriginally posted by Webstormer Quote
Hey guys, I bought myself the Godox TT600 and it works just fine, I like it no complaint at all but I quickly realised that things would not go as I foreseen them to. In short, yesterday I took a few shots for the first time with it and my Godox XPro trigger and - it took me no time to understand this - since the integrayed flash was not popped out, the camera ( K-70 ) considered it as not active ( even if I set it to Always on ) and then raised the sensitivity to 1 200, which gave me an incredibly overexposed photo. My brother paid me a visit for pictures so I took them with no flash and it gave me surprisingly good results for the moment. But I really want to use my external flash beacause with the proper settings on camera results are going to be even way better. Now, the downside of it and the one thing I did not expect at first, I now know that I will have to use my camera in manual mode if I want to have full control of the shooting conditions. You can set the ISO even in auto mode but it will have effects on other settings...

So, I come to you this time to ask if you could recommend me a good tutorial about the manual mode, the way to calculate aperture, sensitivity, shutter speed an power level of the external flash. Thanks in advance once again for your precious help, hype.
Dunno about Godox set-up, but manual flash is straight forward. I'd say no tutorial is necessary. Here goes:

Shutter speed is mostly irrelevant, unless you want ambient light in the photo. More on this later.
In dim lighting.
  1. Starting with aperture priority, choose appropriate value for dof.
  2. Set shutter speed to around 1/200 or 1/160 or so.
  3. Take shot at say 1/8 power and review. Re-shoot with greater or less power or different ISO. Job done.
If not in dim lighting:
  1. Ambient lighting may have some effect on photo as the flash will supply most light, but ambient will creep in. This can be used creatively as movement may not be frozen, for instance - sharp flash frozen, plus some dim movement elements.
  2. Setting as above, but as ambient light is adding to exposure then if not being used creatively, you need to reduce the possible ambient to minimum. This can be done by reducing ISO, narrowing aperture and increasing flash speed to maximum sync. (HSS may be an option)

So manual not too tricky, whereas an ttl/auto mode can be very tricky
05-01-2022, 06:40 AM - 1 Like   #4
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Manual exposure mode on the camera is going to give you most control. In addition to the advice above, set the Flash to P-TTL or TTL (however it is described).

Set the camera shutter speed to 1/180 or slower, and select ISO 200 and a medium aperture say f5.6.-f11. If there is very little ambient light, the flash will provide all the illumination. If you want a combination of ambient and flash, then you may have to use a slower shutter speed or wider aperture, or higher ISO. These will affect the ambient light and the flash will adjust its output accordingly.

05-01-2022, 01:02 PM   #5
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To BarryE and pschlute, I think you both have the right and exact infos I needed. First yes, the shutter speed has no real importance since the flash lighting is so fast it has no impact on picture brightness. And the values you provided me with are the ones I instinctively thought of so you are both, to me, right on again. Thanks a lot - and I mean a lot - to you, guys!

P.S. I have so far not tried the TTL mode but I already experience quite a few times the trickyness of the auto mode. For example sometimes you want the flash to trigger but it wont and other times you would like it not to and it does.

To Pops, I have absolutely no problem with that part of the procedure and I already read a lot of books about photography... The problem is only with calculations, for which my knowledge is not up to date and therefore insufficient. Thanks for trying to help, though.
05-01-2022, 01:57 PM - 1 Like   #6
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As has been said if you are using the off camera flash, then the camera should be approximately 180 shutter speed (possibly 200 is upper limit) or slower. The off camera flash should be set to slave, while having the same group and channel as what the XPro-P transmitter is set to look for. If the flash is set to TTL it will give you the auto exposure, and Manual will provide you the chance to adjust as you would like, which may be the safest if you want overall control using your XPro-P. Also, on my V1, I have to be on the amber colored screen to have it flash, meaning it is in slave mode, I have never had misfires with my Godox lights as long as the settings are correct. I usually set my ISO to 100 or 200 to assure quality images. I know some of the information I am giving you is similar to some that you have already been given, but just wanted to mention it.

Last edited by C_Jones; 05-01-2022 at 02:03 PM.
05-01-2022, 02:06 PM - 1 Like   #7
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Yes, your numbers seem right too and no problem if you confirm others infos. Now, I already know how to use my flash in slave mode and since I've been close to purchase the Godox Ving V860III, I even know how to use it in TTL slave mode, which yes change the backlighting to amber. Thanks to you too, man. :-)


Last edited by Webstormer; 05-01-2022 at 02:16 PM.
05-01-2022, 02:09 PM   #8
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QuoteOriginally posted by Webstormer Quote
Yes, your numbers seem right too and no problem if you confirm others infos. Now, I already know how to use my flash in slave mode and since I've been close to purchase the Godox Ving V860III, I even know how to use it in TTL slave mode, which yes change the backlighting to amber. Yhanks to you too, man. :-)
You're welcome. Thank you.

Have a great day!
05-01-2022, 03:17 PM - 2 Likes   #9
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QuoteOriginally posted by Webstormer Quote
To BarryE and pschlute, I think you both have the right and exact infos I needed
That is good to hear

The important thing to remember is that an exposure with flash consists of two exposures, ambient and flash, both occurring at the same time.

In a non-studio environment, it may be that P-TTL will work best, using the flash compensation on the flash to adjust the flash intensity if needed. In a more controlled studio-like environment then manual flash output is going to give more consistent results, and is what I use. You can get a flash meter or just chimp the results with your histogram.

Either way using the camera in M mode is advisable.

The best thing to do is to get a subject like a soft toy and spend a weekend practising the different ways to light your subject.
05-01-2022, 07:44 PM   #10
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You are right, M mode is necessary in both cases because the camera will not take in account the amount of light brought by the external flash, being able to do it only for the integrated one.
05-01-2022, 09:40 PM - 2 Likes   #11
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Additional tip for Live View: I have a KP, but similar to the K-70, it doesn't have an 'X" setting on the mode dial. Using Manual is fine with the viewfinder, but if you try that in live view, the screen is too dark, showing a preview of the non-flash exposure. As a workaround, One can use TAv mode, with the ISO range set to, e.g. 100-125. This way, you see useful LV image (the camera 'ignores' the ISO constraint in the preview) and ISO stays where you want it to be.
05-03-2022, 10:37 AM - 2 Likes   #12
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QuoteOriginally posted by Webstormer Quote
So, I come to you this time to ask if you could recommend me a good tutorial about the manual mode, the way to calculate aperture, sensitivity, shutter speed and power level of the external flash.
A good tutorial, actually a whole set of lessons, is the Strobist blog here. Press the NEXT link at the end of each page, going through the whole Lighting 101 course. There's a learning curve to master and you need to invest time and exercise.

Very short course:

Prerequisites: The radio trigger is paired with the external flash. Same channel id number, matching flash group letter (let's assume flash group A). Check that it is working, press the button on the trigger and expect to be blinded by a flash burst (if done the Homer Simpson way - just joking). Now attach the radio trigger unit to the camera hotshoe.
Settings:
Camera mode M. ISO 100, aperture F8, shutter speed 1/125 (at the sync speed or below).
Flash in M mode too.
Use the radio trigger unit to modify the power level of "flash A" up/down, to select 1/4 power.
Place the flash at a distance of about 10 feet from your subject. Place the camera somewhere to the side & a bit further away.
Shoot to test. Look at the histogram. Is the exposure ok?
Repeat test with a different power level. Don't touch the camera settings, keep the shutter speed, keep the ISO to 100 (not Auto ISO!), play only with the flash power level.



Now to the way to calculate aperture:

This is based on distance to subject (between flash unit and subject) and a so-called guide number GN (that is actually a power level of your TT600 flash).

Formula: aperture = GN / distance You divide a guide number by a distance. The GN or power setting is the same thing.

The TT600 flash, at full power setting 1/1, has a GN of 197'. Remember 197! Hence, GN is about 100 at 1/2 power and GN is 50 at 1/4 power.
You don't need accurate calculation, just a very rough approximation, to help you to decide if you set F5.6 or F8 instead.

Example: 50 (the GN at 1/4 power) divided by 10 (feet distance) equals 5. Closest aperture is F5.6. Et voilà.
Another example: your distance to subject is between 4 and 5 feet. 50 (the GN) divided by 5 (the distance) gives 10 (the aperture). Set aperture to F11, because that is closer to 10, rather than 8.

Different calculation if you start from a power level of 1/2, that gives you GN 100.

Here are some links to guide number tutorials:
https://www.digital-slr-guide.com/flash-guide-number.html
https://en.wikipedia.org/wiki/Guide_number
Strobist: Guide Number: Your Free Flash Meter

Last edited by CristiC; 05-03-2022 at 10:48 AM. Reason: aperture = GN divided by distance
05-03-2022, 06:17 PM   #13
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I already know the formula for the guide number but your links are so inclusive, covering all points of exposure control, thank you very much, my friend! :-)
05-04-2022, 02:39 PM - 2 Likes   #14
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QuoteOriginally posted by Webstormer Quote
Hey guys, I bought myself the Godox TT600 and it works just fine, I like it no complaint at all but I quickly realised that things would not go as I foreseen them to. In short, yesterday I took a few shots for the first time with it and my Godox XPro trigger and - it took me no time to understand this - since the integrayed flash was not popped out, the camera ( K-70 ) considered it as not active ( even if I set it to Always on ) and then raised the sensitivity to 1 200, which gave me an incredibly overexposed photo.
The TT600 is a single-pin manual-only speedlight. It has no TTL capabilities for the camera/transmitter to control. You can only use it in M. And you can only adjust the power in M from the transmitter (though you could I suppose set the Group to TTL; it will only fire at full power that way, though).

Cameras react different to having flash or not having flash, but the XPro-P on the camera hotshoe should have acted as if you had an on-camera speedlight. But Auto ISO is never really a great idea with flash, because of how cameras tend to react to thinking you've got some ambient settings that are really really dark.

This is just me, but honestly, a TT600 isn't the greatest choice for a first/only speedlight, no matter what David Hobby writes. It's better as a 2nd, 3rd, or 4th off-camera only speedlight. But you want at least one unit you can use on or off-camera. Or at least in TTL. The V1-P, V860 III-P, or TT350-P are your only Godox choices as a Pentax shooter (unlike all the other brands who also get $110 TT685 options). But you could, if you plan to use this flash off-camera all the time) have also used a TT685-C, firmware upgraded to speak P-TTL off-camera (its foot remains Canon-dedicated, though), and gotten TTL control over your off-camera flash.

QuoteQuote:
So, I come to you this time to ask if you could recommend me a good tutorial about the manual mode, the way to calculate aperture, sensitivity, shutter speed an power level of the external flash.
First thing to wrap your head around is that whenever you take a flash image, you're combining two exposures in every shot, because you have two different sources of illumination: the ambient (all the existing light that isn't the flash) and the flash.

Ambient exposure is controlled by iso, aperture, and shutter speed. This you should already know and be comfortable shooting in M before you start up with flash, because the automated system in your camera uses a meter that can only read the ambient light (what's in the scene) before you take the shot. It cannot measure your flash because the burst hasn't happened yet. The reason I say TTL makes it easier is that with TTL, the camera can put the flash into the scene while it's metering with a "preflash", and then adjust the power on the flash to match your other settings. But it can only do that with a flash that speaks P-TTL.

Flash exposure, however, is controlled by iso, aperture, power, and distance. Shutter speed only affects the ambient because the flash burst is much faster than your shutter speed, so leaving the shutter open for longer only gathers more light for the ambient.

Because of these two different sets of controls, you can have two different exposure levels in each image based on the two different light sources. You can balance your flash against the ambient at any combination that's within your flash's power range.

When you rely on automated exposure modes (aperture or shutter priority) on your camera, the camera is most likely going to default to "fill flash"; where most of your exposure comes from the ambient, and only a little from the flash to "fill-in" shadows in bright sunlight. This is a very common use of pop-up flashes and what the camera is designed to default to. If you want to change this, you typically have to be in either the M or P modes on the camera.

Also there is an additional "gotcha" when it comes to shutter speed, which is that every focal-plane shutter has a flash sync speed limit. For most digital cameras, it's around 1/200s. With a K-70, it's 1/180s. Go faster than this without engaging high-speed sync (HSS) mode, and you'll get banding because one or both of the curtains will still be covering part of the sensor when the flash burst goes off. If you do engage HSS, then the flash has to pulse to form a continuous light during the whole of the exposure, and you lose about -2EV of flash power to this. So most folks stick at or slightly below sync speed if they can, to conserve power.

A very typical trick to do flash outdoors with someone is to drag them into the shade, meter and slightly underexpose for the ambient, and then add the flash to light them a little brighter so they "pop" in the frame. But what power setting to use depends on what iso and aperture you're using, how you want to balance the flash against the ambient, and how big/powerful your flash is. If I'm inside, I tend to ballpark iso 400, f/4, and 1/4 power at sync speed, simply because mnemonically it's easy to remember all-4s. Then I chimp, and adjust. With experience, you get to sense what range of power you may need for a given set of settings.

But, as I said, TTL can be a lot easier, particularly at first. You do also need to learn to operate a flash in M, though, just as you need to know how to operate your camera in M, so you can get a sense of what's actually going on. Both Neil van Niekerk's Tangents website, and David Hobby's Strobist website are great places to start.

I typically say start with Tangents and learn on-camera bounce flash first, since it only involves buying and learning a speedlight at first. But the lack of TTL on a TT600 might make that a bit more frustrating than it would be with a V860 III-P ($230) or TT350-P ($85), and the TT350 only swivels 270º which is a completely different PITA for bounce flash. So, possibly starting with the Strobist's Lighting 101 is a better starting point for you.

Last edited by inkista; 05-05-2022 at 10:55 AM.
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