darin_cozine Posted March 28, 2003 Share Posted March 28, 2003 Hello all. I'd like to use my 4x5 to do some macro work.. but one thing I noticed is that the further I extend the lens, the dimmer the image gets. Do I need to adjust my meter readings for macro work? -If so, how? Link to comment Share on other sites More sharing options...
bruce watson Posted March 28, 2003 Share Posted March 28, 2003 http://www.largeformatphotography.info/bellows-factor.html Link to comment Share on other sites More sharing options...
jonathan_bundick Posted March 28, 2003 Share Posted March 28, 2003 Rule of thumb. Bellows extension/focal length = # of stops to open up. For instance: using a 90mm lens at a bellows extention of 180mm = 1:1 would result in 180/90 = 2 Open up two stops from the meter reading. Link to comment Share on other sites More sharing options...
chris_hawkins Posted March 28, 2003 Share Posted March 28, 2003 Hogarth has given you the definitive link. The QuickDisc link within this page leads to a very easy to use and accurate tool. Link to comment Share on other sites More sharing options...
jan_brittenson Posted March 29, 2003 Share Posted March 29, 2003 Remember that 1:1 is 2 stops, then it's all linear from there: 1:2 is 1 stop; 1:4 is 1/2 stop; 1:8 is 1/4 stop. 2:1 is 4 stops, etc. Look at the size on the groundglass and the size in reality and estimate the ratio. Use a ruler if you need to, but extreme accuracy isn't required, within 25% is good enough. My personal approach is to adjust the ISO speed for the magnification and then not think about it. Make sure to compensate for intermediates if you shoot chrome film at 1:3 or higher. For B&W simply add a half stop at 1:1.5 (plus 1.5 stops). Don't forget reciprocity! For much available light studio work you'll be off the charts and will have to guesstimate. (This may affect you to a greater extent than draw, depending on what film you use.) Link to comment Share on other sites More sharing options...
jan_brittenson Posted March 29, 2003 Share Posted March 29, 2003 I forgot to mention another trick to determine magnification. If you have a GG with a grid you can put a ruler in the focal plane (wide open lens) and measure the grid line distance. For example, if you have a 1cm grid and the lines measure as 2cm apart, you're at 1:2. Link to comment Share on other sites More sharing options...
darin_cozine Posted March 29, 2003 Author Share Posted March 29, 2003 Thanks everyone. The excel spreadsheet will work best for me. http://www.largeformatphotography.info/Bell_Ext.xls Link to comment Share on other sites More sharing options...
bob_moulton7 Posted March 29, 2003 Share Posted March 29, 2003 The quick disc will help you; so will the device sold by Calumet. Also useful: . Focus on your object norammly. Then use a tape measure to find the bellows extension from film plane to lens center in inches. What is the bellow extension? Assume here it is 11 inches. Ok, what lens are you using? Assume it is a 210mm. That is about 8 1/4 inch lens. Now translate these number to f stops. From f 8 1/4 to f 11 is about 1 stop. You need about one stop exposure compensation.If the bellows extension if 16 inches, you need a bit less than 2 more stops, etc. For ease you can sew a cloth tape measure into your dark cloth. The devices that are avilable will work, but sometimes you cannot place a totem in the scene or have the time to use the device. this little sytem requires little manipulation. Bob Link to comment Share on other sites More sharing options...
rainer_viertlb_ck Posted May 9, 2003 Share Posted May 9, 2003 use the sinar or gossen metering behind the screen glass...........works easy and compensates everything... Link to comment Share on other sites More sharing options...
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