Focal Length Comparison Chart for Whole Plate?

[Greg]

Have found several Focal Length Comparison Charts covering from 35mm up to 16x20 but none of them list the 6.5" x 8.5" Whole Plate format. Anyone know of a Focal Length Comparison Chart that includes the Whole Plate format?
Thanks

[Greg]

Wanted to mark my Linhof Universal Viewfinder with the lenses I use for Whole Plate photography. The finder is labeled for use with the 4x5 format with the 4x5" mask on the front. Now the aspect ratios of the 4x5 and Whole Plate formats are not exactly the same but close enough for me to use the finder to preview a scene. I used the longest dimension of each format to compare them to each other.

Here's what I determined:
180mm lens on WP is equal to using a 74mm lens on 4x5
250mm lens on WP is equal to using a 100mm lens on 4x5
355mm lens on WP is equal to using a 140mm lens on 4x5
508mm lens on WP is equal to using a 200mm lens on 4x5

[lucaas]

Hi Greg,
The diagonal length of WP is 271.8mm, which is about 1.67 times longer than 4x5's. So 180mm on WP is 180/1.67=108mm on 4x5.
250mm/1.67=150mm
355mm/1.67=213mm
508mm/1.67=304mm

[Greg]

Hi Lucaas,

Since the diagonals (aspect ratios) of WP and 4x5 are not equal, I chose to start with matching the 8 1/2" dimension of the WP format to the 5" dimension of the 4x5 format on my Linhof Universal finder. Mounted each of my lenses on my WP camera and matched the longer dimension views of my lenses to the finder. That's how I determined the "equivalent" (4x5) views. Next I am going to take the smaller 56x72 front aperture/format mask and mark the longer 5" dimension to match the 5" dimension of the 4x5 aperture/format mask. Then determine the correct smaller dimension of the WP aspect ratio and mark it on the 56x72 front aperture/format mask. Really carefully with a Dremel cut out the new WP aperture. When I place this WP aperture/mask on the Linhof finder, I will be able to accurately frame the WP view with it by using the "equivalent" 4x5 focal lengths marked on the finder.

[Taija71A]

Here's what I determined:
180mm lens on WP is equal to using a 74mm lens on 4x5
250mm lens on WP is equal to using a 100mm lens on 4x5
355mm lens on WP is equal to using a 140mm lens on 4x5
508mm lens on WP is equal to using a 200mm lens on 4x5

Greg, please be advised that your math is way-off and that the above cited determinations are not correct.

Since the diagonals (aspect ratios) of WP and 4x5 are not equal, I chose to start with matching the 8 1/2" dimension of the WP format to the 5" dimension of the 4x5 format on my Linhof Universal finder...

Okay. 8.5 / 5 = 1.7
However, your respective ratios for the 'Nominal' Film Dimensions are in between 2.43 and 2.54
--
Thank-you. -Tim.

[Greg]

I'm sure you are correct, the math is off... I wasn't dealing with format diagonals. What I simply wanted to do is to be able use my Linhof Universal finder with my WP camera. The universal finder now sports a WP opening in its viewfinder mask (replacing the viewfinder mask with the 4x5 opening). So now if I want to accurately view what my 355mm lens projects on the WP's GG, all I have to do is rotate the (4x5) focal length ring on the finder to the 140mm setting. I was pleasantly surprised at how accurate the framing in the finder was for all my WP lenses.

[RJ-]

Hi Greg,
The diagonal length of WP is 271.8mm, which is about 1.67 times longer than 4x5's. So 180mm on WP is 180/1.67=108mm on 4x5.
250mm/1.67=150mm
355mm/1.67=213mm
508mm/1.67=304mm

Lucaas - your maths is great. However the 271.8mm calculation assumption is based on the whole area hypotenuse of the whole plate image. The actual film rebate renders approximately 266mm as a more accurate guide for the diagonal length, if you are using modern Chamonix/Argentum derived whole plate holders, or the old Kodak Century wholeplate standard - which I'm guessing - most of us are, thanks to Sal Santamaura's work, otherwise we would all be conflicted with multiple non-standardised holders and variable rebate edge dimensions.

Greg - that's quite an effort to previsualise the whole plate format. The lengths you've gone to recall the built in Silvestri sports viewfinders for rapid visualisation. I presume you've made a dremel cut masking aperture for each focal length?

All the best with the endeavour. I've not found 5" x 4" format to be a very satisfying reference format, since it is only one of many rectangular ratios and overtime, artistic vision becomes crippled if whole plate work is reduced back to referencing to 5" x 4" equivalent fields of perspective although as far as mechanics go, I find my pre-visualisation limited to the use of both left and right index fingers and thumbs to form a very non-technical viewing rectangle.


Good luck with the whole plate shooting!

Kind regards,
RJ

[Sal Santamaura]

...The actual film rebate renders approximately 266mm as a more accurate guide for the diagonal length, if you are using modern Chamonix/Argentum derived whole plate holders, or the old Kodak Century wholeplate standard - which I'm guessing - most of us are, thanks to Sal Santamaura's work...

Aw shucks, thanks. However, the image area diagonal of a negative made in a Chamonix whole plate holder, as measured moments ago using a steel rule, is 260.5mm. I usually round to 260mm.

[lucaas]

Lucaas - your maths is great. However the 271.8mm calculation assumption is based on the whole area hypotenuse of the whole plate image. The actual film rebate renders approximately 266mm as a more accurate guide for the diagonal length, if you are using modern Chamonix/Argentum derived whole plate holders, or the old Kodak Century wholeplate standard - which I'm guessing - most of us are, thanks to Sal Santamaura's work, otherwise we would all be conflicted with multiple non-standardised holders and variable rebate edge dimensions.

Hi RJ,

Thanks for pointing this out.

Xing

[RJ-]

Hi Lucaas,

No problem, but I'm afraid I'm still experiencing a few millimetres of variation as Sal rightly points out!

Aw shucks, thanks. However, the image area diagonal of a negative made in a Chamonix whole plate holder, as measured moments ago using a steel rule, is 260.5mm. I usually round to 260mm.

Hi Sal, great to see you are still here on this forum. I've finally got around to shooting the Tmax400 whole plate (remember that) after a long sabbatical!

Is your steel rule calibrated to international ANSI standards

(j/k)


260.5mm appears very short, however I suppose - may this be due to manufacturing tolerances which are less critical dimensionally on the actual image area, than for the T depth where the film plane tolerances are required for accurate focus.

The majority of my actual exposed whole plate images (over several hundreds) have a diagonal measurement of approximately 262-3mm, excluding 2 Chamonix whole plate holders which developed light leaks. I haven't checked them all, however there are a few WP images where the image area diagonal is as narrow as 260.5mm.

The 260mm makes sense since the Schneider Super Angulon 90mm XL f5.6 covers the whole plate image negative at infinity. Perhaps the manufacturer specification for covering power of 110 degrees and a 259mm image circle is very conservative.

I find 266mm to be a safer whole plate minimum image circle coverage reference number for the rather imprecise Chamonix whole plate camera, which is very hard to zero align accurately or quickly. It isn't very enjoyable working with such tight tolerances in the field, although there are so few alternative wide-angles like the SA 90mm XL f5.6 which does cover whole plate, if the bed drop or front rail can be overcome. Since I've switched to using the Argentum WP Explorator, it feels more technically accomplished and less of a strain to work with such narrow covering powers.

Kind regards,
RJ