Originally Posted by thisispants
The MG in MGIV stands for "multigrade". This means you can change the contrast "grade".
A set of filters will give you grades between very low contrast (00) through low contrast(0.5, 1, 1.5) normal contrast (2, 2.5, 3) and high contrast (4, 4.5, 5). This will vary slightly between filter sets.
You can achieve even more intermediate contrast grades by combining multiple exposures through different filters.
Exposing with no filter will generally give you contrast similar to using a No. 2 filter.
Hope this helps!
“Photography is a complex and fluid medium, and its many factors are not applied in simple sequence. Rather, the process may be likened to the art of the juggler in keeping many balls in the air at one time!”
Ansel Adams, from the introduction to The Negative - The New Ansel Adams Photography Series / Book 2
If you are doing that, you have turned your enlarger into an ensmaller.
Originally Posted by BetterSense
HAHA I had a good chuckle.
Originally Posted by Steve Smith
f5.6 to f8 are good general apertures to use, but test for yourself, going any smaller may cause diffraction and increased exposure times.
Ive left RC papers sit in coffee and wine for 3 days once to test if they were toneable, only the slightest separation at the edges with red wine.
all the exposure principles are the same, halve the aperture, double the time. raise or lower the head and the time changes as well.
Use test strips. It will save you much paper.
I'm new to these forums as well, but I think I can chime in a little bit.
Another practical consideration about aperture that I haven't seen addressed is print time. If you're making a relatively small print (4x6, etc), you may find it good to stop down a little bit more on the enlarging lens. If your enlarger timer is as bad as mine, the +- .5 seconds of error in the device can make a real difference on a very short exposure time! I try to avoid these ultra-short exposure times by stopping down a bit more.
Also, about the enlargement size vs time question. A great way to think about it is by print area, as was mentioned previously. However, I often record the height of the enlarger, not the printing area, because I often end up putting a slight crop on my negatives, which I may not get exactly the same the next time I print.
Because the aperture of the camera is fairly small in relation to the paper, it follows this wonderful photographic rule known as the inverse square law. Simply put, the ratio between the old time and the new time is equal to the division of the new height squared divided by the old height squared. So, if I had an exposure time of 8 seconds at 12 inches, if I raise the enlarger head to 16 inches, my new time would be 8*((16^2)/(12^2)), or approximately 14.25 seconds. Hope that makes a bit of sense!
Rochester Institute of Technology 2013
Imaging and Photographic Technology and Imaging Science
RIT Photo House Fundraising Chair 2011-2012
N80, XA, Rolleiflex 3.5f
About size and exposure....
In theory and also in reality, calculation based on area works. Double the area, double the exposure time.... But! (there's always BUT!) our eyes and brain don't always work that way. Calculation will give you a good starting point but when you change size drastically, (even double or half) to end up with best looking print and "feel the same" print, you may need to alter the exposure a bit. You may want to find a comfortable size like 8x10 and stay with it for a while.
One of the great thing about using filter is, for commonly used range, say 00 to 3.5, exposure stays pretty much constant. That is, you can slip a different filter and expect about the same print except for contrast for the same timing. If you don't use filter, you get equivalent of #2 but time will be extremely short. If you want to change the contrast, you have to do the test print all over again. My suggestion is to always use a filter.
Develop, stop, fix.... wait.... where's my film?
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Something I wish I'd done sooner is get either a timer or a surge protector with a switch on it. That way you're not inadvertently jostling the enlarger head around when you switch the thing on and off.
The Ilford multigrade paper is actually three separate emulsions. One is sensitive to blue light, while the other two are sensitive to varying levels of green light as well. If you use a magenta filter, some green light is cut out, so all three of the emulsions function at the same speed and add together, creating a high-contrast image. A yellow filter on the other hand will remove some of the blue light, so the layers will work at different speeds, creating a softer image with less contrast. The stronger the filter, the stronger the effect. No filter at all gives you average contrast. Ilford's got a PDF up on their site explaining the whole system if you feel like geeking it up in geeksville.
Originally Posted by thisispants
That's only true if the aspect ratio remains unchanged.
Originally Posted by tkamiya
For example, if you make a 4x5 print with an exposure of X seconds, you can make an 8x10 print (four times the area) at a 4X time.
However, if you make a 1x10 print, like a panorama, its area is only 1/2 that of the 4x5 print, but the exposure must be 4X, just as for the 8x10 print.
Great, this is good stuff.
Just one last question:
With regard to focusing... I've seen a few posts here which mention that when focusing the image, you actually focus on the grain as opposed to the actual image...
Is this true?
Yes you focus on the grain. If you can get hold of a grain focuser, you can see when the grain is in focus - try focussing by eye first and then focus using the focuser, and you're sure to see a difference.