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12-22-2019, 06:03 PM   #16
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QuoteOriginally posted by morenjavi Quote
I noticed 0.3EV difference by setting 200j or 400j, tested AD200 and AD400Pro.
That is surprising.

Did the manual conversions result in the same exposure compared to the TTL exposure?

Were the AD200 and AD400 Pro exposures identical?

If both of the above are true, the AD400 Pro would only produce 0.3EV output for the same manual power level.

12-23-2019, 02:56 AM   #17
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QuoteOriginally posted by Class A Quote
That is surprising.

Did the manual conversions result in the same exposure compared to the TTL exposure?

Were the AD200 and AD400 Pro exposures identical?

If both of the above are true, the AD400 Pro would only produce 0.3EV output for the same manual power level.
Just to clarify, I tested one flash at a time, flashes have different modifiers etc. For example, if I'm testing the AD400, I take two TTL exposures with TCM settings at 200j & 400j. Also I compare the exposures converted to manual. Exposures seem more or less good regardless of the TCM setting. Then I test the AD200 and repeat the measures. I'm not comparing AD200 exposures against AD400 exposures. For the same flash, changing TCM settings, I found 0.3EV difference.

I'll repeat the tests using the same modifiers, distance, etc, and willl compare AD200 vs AD400 exposures. Also I'll use the photometer to have a reference of a good exposure.
12-23-2019, 09:07 AM   #18
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Well, I made the tests. I found a very collaborative subject (daughter's doll )

I setup the AD400 and AD200 + AD-B2. I put a subject with a light background. I used a 60cm round softbox to illuminate from the side, A light wall served as a bounce card from the other side. I centered the subject and used center-weight mettering on the camera. Camera's settings was f5.6 1/160 ISO100, flash WB.

First I took a measure with my photometer to get f5.6. Photometer was pointing to camera.
Second, I set the TCM to 200j and took a TTL pic, then changed to manual with the TCM button and took another pic.
Last, I set the TCM to 400j and repeated.

I did the tests with the AD400pro, then I swapped it for the AD200+AD-B2. I tried to set the softbox at the same heigh, distance and orientation, but maybe, there was a bit error margin.
Camera used Pentax K3-II, Xpro-P trigger.

These are the results:

AD400pro ISO100 F5.6

a. Photometer measure: 1/32 + 0.7 (f4.0 9)
b. TTL & 200j, TCM gives 1/64 +0.7
c. TTL & 400j, TCM gives 1/64 +0.7


AD200 ISO100 F5.6

a. Photometer measure: 1/8 (f4.0 9)
b. TTL & 200j, TCM gives 1/32 +0.3
c. TTL & 400j, TCM gives 1/32 +0.3

I took a total of 5 + 5 pics (that I'll upload later) +1 BTS scene.

Preliminary conclusions:

* AD400 is more powerful/efficient than 2 x AD200 + AD-B2. AD200 needed +1.3EV to get the same exposure than the AD400. You should expect 1.0 EV difference. Maybe the AD-B2 reflective surface is not as efficient as the AD400's. Notice that this can't be a general conclusion, because I have only a AD200 sample, and my measurement can have some error margin.
* TCM setting (200j or 400j) seems to have no effect regardless you use the AD400 or AD200. Most of the mesaures show no difference, but one time I got 0.3EV difference.
* TTL exposures seems a bit darker compared to manual ones calculated with TCM (you'll see in the pics I'll upload later)
* I got the best exposure with the photometer. This is expected. Notice that the white background can also confuse the mettering. AD200 TTL seems to need more compensation than AD400.

In a digital world, TTL exposures can be recovered without issue, and TTL can be convenient in a sense that you can quickly get an image that are not too over or underexposed (it can save you the day); but, at least with Pentax TTL, the photometer still have the advantage.

Regards,
Javier.
12-23-2019, 10:17 AM   #19
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Hello again.

Here are the images. AD200, AD400 and the BTS. There are some minor variations between TTL and TCM calculated values, sometimes TTL seems a bit darker, sometimes a bit brighter. Images are cropped, so original images have a lot more of white background. Maybe is the main cause TTL is underexposing so much.

You have to read every batch this way:

--------------------------- TTL measure 200j ------------ TCM measure
Photometer measure
--------------------------- TTL measure 400j ------------ TCM measure


Enjoy .

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PENTAX K-3 II  Photo 
12-25-2019, 06:47 PM   #20
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My AD400 Pro is perfect for me when considering size/weight and output. It allows me to cover all of my needs.
12-26-2019, 02:32 AM   #21
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QuoteOriginally posted by dcpropilot Quote
My AD400 Pro is perfect for me when considering size/weight and output. It allows me to cover all of my needs.
Thanks for sharing, It's now my favourite and most powerful light. The only point not so great is the umbrella holder, the umbrella remains a little loose, I don't know how it will be after months of use. Out of this, I think it's a fantastic light.
12-26-2019, 10:57 AM   #22
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QuoteOriginally posted by morenjavi Quote
Thanks for sharing, It's now my favourite and most powerful light. The only point not so great is the umbrella holder, the umbrella remains a little loose, I don't know how it will be after months of use. Out of this, I think it's a fantastic light.
You may be able to use a clip or something similar to prevent it from sliding out. Not sure it's like this other than perhaps the umbrella would give (if the lightstand falls) and help prevent the strobe from breaking.
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