Digital SLR Flashes

galla47

Hello everyone.. I've enjoyed reading posts here, but it's time to participate: so I have a question about external flash units and Digital SLRs.

For purposes of argument, I have a Nikon D50, which has a focal legnth multiplier of 1.5. This means that a 35mm lens on this camera will give me the equilivent of 52.5mm on a 35mm film system.

So now, enter the SB-600 external flash with a zoom head. When I zoom the lens to the 35mm setting (getting the 52.5mm equilivent field of view on film), shouldn't the flash head also zoom to the 50mm setting? Right now, it zooms to 35.

What I'm thinking is that I'm "loosing" range on my flash with focal legnths under 85mm (the furthest zoom the flash has) because the flash is lighting a wider FOV than needed.

Another concern I have is that the widest zoom the flash has is 24mm (without flipping down the difuser), but my kit lens is a 18m (27mm equiv.). Seems to me that the flash should work just fine at the 24mm setting, becuase it is guaged on what a 35mm full frame sensor.

Does this make sense to anyone? Should Nikon re-program the firmware to add in the 1.5 multiplier setting to the focal distance to the flash? What do other dSLR systems do?

JamesJWeg

Ummm, I run the SB-600 on my D70 with 18-70mm DX lens and it works fine, I also use that same flash on the D2H with the sigma 70-200 and have no problems, I'm not sure if you are saying that you have an actual problem or if this is a theroy question.

James.

galla47

More of a Theory question...

In "theory" I wonder if I am loosing range on my flash because it is not zoomed as far as it could...

Conversely, on the widest setting, am I not covering the entire FOV of the 18mm lens unless I put the dispersion filter down?

I imagine one of these is a true statement, but not sure witch.. I'm thinking the first one.

JamesJWeg wrote:

Ummm, I run the SB-600 on my D70 with 18-70mm DX lens and it works fine, I also use that same flash on the D2H with the sigma 70-200 and have no problems, I'm not sure if you are saying that you have an actual problem or if this is a theroy question.

James.

JamesJWeg

Is your lens a DX series? that would enter in.

James.

galla47

Yes... the 18-55 DX that comes in the D50 kit. Not sure why that would matter though...

My point is that the FOV that the 35mm lens provides on the dSLR is equilvent to a 52.5mm lens on film. Shouldn't the flash zoom to the film equilvent in order to match the FOV angles? I would think this would apply at the 35mm legnth on the DX lens or on a non-dx lens that is also zoomed to 35mm (provided both are mounted on a camera the 1.5 conversion ratio).

JamesJWeg wrote:

Is your lens a DX series? that would enter in.

James.

JamesJWeg

Check the info on the DX lens, if I remember right they do not have the 1.5 crop factor, They are bult for digital, not film.

James.

JamesJWeg

http://support.nikontech.com/cgi-bin/nikonusa.cfg/php/enduser/std_adp.php?p_faqid=2596&p_created=1053428342&p_sid=Ot*IFJPh&p_lva=&p_sp=cF9zcmNoPTEmcF9zb3J0X2J5PSZwX2dyaWRzb3J0PSZwX3Jvd19jbnQ9NiZwX3Byb2RzPTgxLDgzJnBfY2F0cz0wJnBfcHY9Mi44MyZwX2N2PSZwX3NlYXJjaF90eXBlPWFuc3dlcnMuc2VhcmNoX25sJnBfcGFnZT0xJnBfc2VhcmNoX3RleHQ9RFg*&p_li=&p_topview=1

James.

galla47

I'm still not sure what the DX has to do with it...

If I take the DX lens or my non DX lens and zoom them both to the 35mm setting, the field of view would be the same.

Khaos

galla47 wrote:

I'm still not sure what the DX has to do with it...

If I take the DX lens or my non DX lens and zoom them both to the 35mm setting, the field of view would be the same.

I do believe that Canon flashes like the 580EX take into account the FOV crop factor for cameras like the 20D. So the range is adjusted accordingly when using ETTL. If this is done on Nikon I'm not aware, but I do know the 580 handles it.

ScottMcLeod

galla47 wrote:

I'm still not sure what the DX has to do with it...

If I take the DX lens or my non DX lens and zoom them both to the 35mm setting, the field of view would be the same.

Are they? Because an 18-55 DX lens should have a field of view comparable to that of a 28-90 35mm lens...

I took a 55-200 DX lens and put it onto a F75 body the other day, and it was a 55-200, but on the D50, it definitely was hitting a further telephoto range. (75-300, approx, as defined by the 1.5x)

I'm pretty sure that the SB-600 and 800 compensate for it.