Focus Register - Wista 6x12 v Fidelity 4x5

[Paul Tomkins]

Hello. I have just found this great site and have checked through the threads b ut don't seem to be able to find one that matches my enquiry. (sorry if it has b een previously covered missed it) I am shooting with a sinar f and have adjusted the groundglass to give spot on f ocus with my Wista 6x12 rf back (this back is great to use - no problems) howeve r, I often shoot 4x5 loaded into Fifelity holders, at the same time, switching b etween one and the other during the shoot. My problem is that I have to shift th e focus back (extended) by 1mm to ensure that the focus is ok on the sheet film. I can't work out how I can get around this - any ideas? It seems amazing that this discrepancy is so great. Anyone had simmilar experiences? Tha nk you, Paul Tomkins amaazing that

[paul owen]

Hi Paul I've never heard of a problem like this - but there must be some other sufferers? Have you tried another make of sheet film holder?

[Paul Tomkins]

I am sorry to say that I have was wrong to identify the RFH as a Wista, it is in fact a Horstman. (my 6 x 9 holders are Wistas and I just confused the 2. I don't often now use the Wistas so am not sure about any problems with their focus registration) In response to Paul's answer, I could try other 5x4 holders but as I bought 15 holders before the Horstman RFH, I have quite an investment there. It just seems crazy that all the manufacturers don't seem to make stuff to a common spec. Paul

[neil poulsen]

Something is fishy somewhere. For a distance of 1mm, which is large, I would think that there's a problem either with the camera or with the Horseman 6x12 film holder. It sounds like it's with the holder.

Have you tested different holders to see if they exhibit the same problem. Also, there's data, e.g. in some of the Q&A threads on Wisner's site that give the prescribed offsets between the plane of the holder that rests against the camera when in place and the film plane. You could measure the holder to see if this offset is correct.

Which way do the 6x9 holders favor? With the camera adjusted to optimize focus for the Horseman 6x12, do you still need to make the 1mm adjustment for the Wista 6x9 holders?