Zoom numbers on Yongnuo YN560 Speedlight?

<p>On the YN560 speedlight, the 'zoom' numbers range from 24 to 105. Just what do the numbers refer to in terms of flash emission? Is there any correlation between these numbers and the range of zoom lenses that say, range from 24mm to 105mm, or is it something else entirely? I know that this info. is covered in the 'manual' but it ithe info is confusing to me. Thanks.</p>

<p>(P.S. This is not an endorsement or critique of this flash. I just want information). Thanks.</p>

 

<p>I'm not familiar w/ the Yongnuo but in general, it relates to the optimum coverage for a lens of that focal length. On the Nikon flashes, the reflector/flashtube assembly moves to change the light coverage so obviously, if you're using 24mm lens, the usable distance is less vs. 105 etc etc. Of course, you could use it as a marginal snoot to change the emphasis of light</p>

<p>I assume that it refers to the Angle of View of lenses of that focal length on a full frame camera .... if a FF owner would have a YN, like me with my M4/3 :-) I think they are a neat unit, far better than anything I have owned previously. I also have a 468 for my Canon.</p>

<p>The useable distance doesn't change, just the f/stop :-)</p>

I'm also not understanding how to use the zoom numbers, which in the Yonguo manual are said to be in mm and refer to focal length.

 

Do the numbers refer to the focal length of 35mm camera lenses or specifically to DSLR lenses?

 

I am using the flash with a 6 x 6 medium format film camera, with a "normal" 80mm lens. How do I convert the zoom numbers to

correspond to my lenses (50, 80, 150mm)?

<p>multiply the setting on the flash by 1.8 or divide your lens focal length by 1.8. For example<br>

50mm lens= 27 on flash. May be OK to set for 28<br>

80mm lens=44 on flash. You would need to set to 35<br>

150mm lens=82 on flash. It would be fine to set to 70 or 80 on flash.</p>

<p>Zooming the flash will allow it focus the light into a smaller area allowing it to be used at a greater distance. The numbers refer to the focal length of lens that the flash will provide good coverage for. It most likely assumes a full frame camera.</p>

<p>To answer Ben:<br>

Use a field of view table (or if you are mathematically inclined there are formulas online also). First find the FOV for your MF lens (6x7 is close enough to 6x6). Then find the focal length of a FF camera that has that FOV.<br>

Example, say you have a 100mm MF lens, the FOV is 38.6 degrees. The closest FOV to this for a FF camera (24x36mm) is 39.6 degrees, corresponding to a focal length of 50mm. Set the flash zoom to 50mm.<br>

<a href="http://www.pentaxforums.com/forums/pentax-lens-articles/93714-field-view-tables-aps-c-24x36-645d-645-6x7.html">http://www.pentaxforums.com/forums/pentax-lens-articles/93714-field-view-tables-aps-c-24x36-645d-645-6x7.html</a></p>

<p>The questions and possible problems were answered by Nikon SB910 flash, when used with compatible Nikon DSLR camera.</p>

<p>If other conditions are met, e.g. flash head is in straight ahead position, no diffusers, etc.<br /> then the flash head automatic zoom feature adjusts to match angle of view current setting of a compatible zoom lens position used. The flash also recognizes if the camera has a DX or FX sensor size, (or if DX mode is used on FX camera), and also does additional flash beam angle adjustments, as appropriate.</p>

<p>Not sure if Yongnou flash has all the same flash features automated or manual (?), as those built into the SB910 Nikon flash.</p>

<p>Beam concentration that matches angle of view of a zoom lens position, with respect to camera sensor size, - if all done right as in SB910, results in less loss on unnecessary side/edge light, faster flash recycling, and longer battery life, as well as faster shooting consecutive pictures in the fast motor-drive like mode.</p>

<p>The beam concentration makes brighter lighting and thus allowing longer maximum shooting distances as well, especially important when shooting in manual mode and the subject is farther away than the max CLS/iTTL automatic range of 20 meters (or 66 ft).</p>

<p>What does the SB910 have that a YN560 doesn't ? :-) <br />I know it doesn't work with the camera to achieve the correct exposure but with 64 levels of output and ability to ignore pre-flashes amongst other things it is a pretty swept up beastie :-)<br />To work out the angle of view of the MF lenses draw a line 2.5 inches and place a point 80mm ahead of it over the mid-point of the line. connect point to ends of line and that is the AoV of the lens. Repeat for 35mm lenses and you can compare and relate each to the other.<br>

Is MF 2.25 x2.25 or 2.5x2.5 ? So long since I used it I forget :-(</p>

<p>As Matthew, JC and Howard said, the "zoom" numbers refer to the coverage angle of the flash compared to a lens of that focal length on the 35mm film format. At the 24mm setting the flash should cover a horizontal angle of at least 74 degrees; at the 35mm setting 55 degrees; at the 50mm setting 40 degrees, and so on. This has almost nothing to do with the output power. Also expect some falloff towards the edges of that coverage angle.</p>

<p>The apparent power will increase as the coverage angle decreases, but not by as much as the maker would have you believe. There's no way you'll get a real guide-number of 56 (100 ISO/metres) out of <em>any</em> little hotshoe flash. For example a genuine Nikon SB-900 manages a true GN of about 27 at the 35mm setting (makers claim GN 34) and a real GN of around 36 at the 105mm setting (claimed GN 49.5). Makers GNs need to be taken with a large pinch of salt and a good sense of humour.</p>

<p>JC. The true size of the 6x6cm format is around 56 by 56 mm. But the 35mm format has a ratio of 3:2, so the vertical angle is 2/3rds of the horizontal angle. To cover the AoV of an 80mm lens on 6x6cm you'd need to set the flash at its 35mm zoom setting or thereabouts.</p>