AF360FGZ flash and Zoom values

[wiseman]

I recently purchased the AF360FGZ and am very happy with it. It is vastly better than the K10D built in flash and I can also use it on my Pentax ZX-5n film camera!

The K10D manual states (pg. 180):

The AF360FGZ does not have the function to set the FORMAT size to (DIGITAL), but the difference in angle of view between standard 35 mm format and the K10D is automatically calculated based on the focal length of the lens used (when using DA, D FA,FA J, FA, or F lenses ). The conversion indicator appears and the format size indicator disappears when the exposure metering timer of the K10D is on (it return to 35 mm format display when the exposure metering timer is turned off).

A table follows this paragraph in the manual but I could not copy it here.

I do not understand this. It looks like the zoom number in the flash LCD shows the sensor corrected lens focal length (e.g. 20mm lens displays as 28mm) only when the K10D's metering is off. When the shutter release is half pressed and the metering is on, the zoom number in the flash LCD then changes to a wider value (e.g. with the 20mm lens, the 28mm changed to 19mm).

I must be missing something, could one of you please explain what this is all about?
Thank you,

[Canada_Rockies]

Originally Posted by wiseman

I recently purchased the AF360FGZ and am very happy with it. It is vastly better than the K10D built in flash and I can also use it on my Pentax ZX-5n film camera!

The K10D manual states (pg. 180):

The AF360FGZ does not have the function to set the FORMAT size to (DIGITAL), but the difference in angle of view between standard 35 mm format and the K10D is automatically calculated based on the focal length of the lens used (when using DA, D FA,FA J, FA, or F lenses ). The conversion indicator appears and the format size indicator disappears when the exposure metering timer of the K10D is on (it return to 35 mm format display when the exposure metering timer is turned off).

A table follows this paragraph in the manual but I could not copy it here.

I do not understand this. It looks like the zoom number in the flash LCD shows the sensor corrected lens focal length (e.g. 20mm lens displays as 28mm) only when the K10D's metering is off. When the shutter release is half pressed and the metering is on, the zoom number in the flash LCD then changes to a wider value (e.g. with the 20mm lens, the 28mm changed to 19mm).

I must be missing something, could one of you please explain what this is all about?
Thank you,

The flash is changing its zoom to match the smaller size of the APS-C sensor on the digital camera. With a 50mm lens on 35mm, the flash would set to cover the 35mm (24x36mm) format at 50mm. For the smaller sensor, the flash should set itself to about 75mm. You get more reach with the APS-C sensor for the same lens, because the flash need not cover the area outside the sensor which would be included in the 35mm exposure frame size.

Clear as mud?

[Lowell Goudge]

what I have never been able to figure out is how the K10D sets the zoom and format.

I understand the flash is trying to set the zoom to the correct equivelent focal length for coverage, but it behaves differently in this manner depending on whether I have a pentax zoom or after market zoom.

I generally just ignore it. I have never had an incorrect coverage shot, and could never get a good answer from pentax so I gave up

[Canada_Rockies]

Originally Posted by Lowell Goudge

what I have never been able to figure out is how the K10D sets the zoom and format.

I understand the flash is trying to set the zoom to the correct equivelent focal length for coverage, but it behaves differently in this manner depending on whether I have a pentax zoom or after market zoom.

I generally just ignore it. I have never had an incorrect coverage shot, and could never get a good answer from pentax so I gave up

The camera tells the flash the zoom setting, so perhaps not all after market/ third party lenses actually tell the camera, and via the camera the flash, what setting it has. With Pentax lenses, A series and up, there should not be a problem. The flash defaults to 35mm, I think (my AF500FTZ does), so coverage should be adequate for most cases, although the reach may be shortened.

[Lowell Goudge]

Originally Posted by Canada_Rockies

The camera tells the flash the zoom setting, so perhaps not all after market/ third party lenses actually tell the camera, and via the camera the flash, what setting it has. With Pentax lenses, A series and up, there should not be a problem. The flash defaults to 35mm, I think (my AF500FTZ does), so coverage should be adequate for most cases, although the reach may be shortened.

No, what was confusing was that my SMC 18-35 FA-J and my 10-20 when used with the flash displayed the actual lens focal length, but the SMC 28-105 and 28-70 FA Power zoom lenses displayed the ASP-C equivelent focal lengths for the length I selected.

I think what really happens is that the flash has only a set number of preset zoom ratios, and the 28-80 and 28-105 were just below a transition point, and as a result the mins and max focal lengths the flash displayed were confusing, where as the 10-20 and 18-35 were on the other side of a transition, and the results made sense

[wiseman]

Here is the table from the K10D manual.

Flash.jpg

As you can see, with a 50mm lens on the K10D, the flash LCD displays 70mm if the camera meter is off. Once the camera meter is on, the flash LCD displays 48mm. The flash zoom mechanism does not actually zoom in or out when the shutter release is half pressed. Yet, the LCD is displaying a different zoom value when the shutter is half pressed.

With my 43mm lens the LCD displays "35mm" under FORMAT and displays a A.Zoom value of 50mm. The 43mm acts like a 65mm and the flash is choosing 50mm because it is the next increment setting at or below 65mm. Half pressing the release button and the "35mm" under FORMAT disappears and the A.Zoom value changes to 34mm. This is the part I do not understand. What does the 34mm represent? The lens is a 43mm, the closest flash zoom increment is 35mm, and the lens is a 65mm with crop factor.

p.s. the flash zoom increments are: 24 - 28 - 35 - 50 - 70 - 85