enlarging lens / unsatisfacory prints

Discussion in 'Enlarging' started by CPorter, Dec 7, 2006.

  1. CPorter

    CPorter Member

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    The title emplies these are related, not really, just have two separate questions.

    First: I see lots of text that says that a normal enlarging lens for 6x7 format should be 90mm. Is there any advantage to using a 100mm or 105mm? Any disadvantages? Fred Picker says that image quality will be sharper by using a lens that is larger than what is considered "normal".

    Second: Your prints that are not satisfactory from any given darkroom session, do you hold on to them in a file for all documentation of the session or throw them away? throw some of them away? Basically, how much of unsatisfactory prints, if any, do you hold on to after you have reached the final, acceptable print? Just curious.

    Thanks
     
  2. TheFlyingCamera

    TheFlyingCamera Membership Council Council

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    For the first question...

    the reason a larger than "normal" lens is recommended is that the lens' circle of coverage is larger than the negative, so you will have full, even illumination of the negative and the corresponding print on the baseboard. The downside is that you're putting the negative farther from the baseboard to make the same size print, so you're increasing the exposure time as well.

    For reject prints... I keep them around until I've got my good finished print... they serve as a reference so I can see where I'm coming from, and where I'm going to with the print. I make notes on the backs as I'm working so I know what succeeded or didn't about that particular print.
     
  3. ronlamarsh

    ronlamarsh Member

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    Reject prints

    I have heard the same explanation for using an enlarging lens just a little longer than normal so that you are in the center of coverage. I use a 150 for 4x5 and a 210 for 5x7.
    I save as many of my rejects as possible to use as tests for toning etc.
     
  4. Konical

    Konical Subscriber

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    Good Evening, Chuck,

    I agree that the rejects should usually be saved. Completely fixed and thoroughly washed, they have another useful function which hasn't been mentioned. If you drymount prints, placing a reject (or just a blank sheet of thoroughly processed paper) on the back side of the mount board will balance out any curling tendency.

    Also, if you have occasion to use prints in a situation where they will be routinely passed around or handled, simply drymounting a waste print on the back of the "user" print makes a nice stiff package which holds up to handling better than an unmounted print; again, the opposing pull forces of the back-to-back sandwich balance and make for good flatness. All this can apply either to fiber or RC materials.

    Konical
     
  5. Nick Zentena

    Nick Zentena Member

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    Longer lenses are great when you're making smaller prints. Gives you a little extra room. OTOH if you're making big prints the long lens will limit you.
     
  6. firecracker

    firecracker Member

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    105mm lens can cover up to 6x9cm negs.

    Reject prints are nice to have because you can see your growth and progress in them over time.
     
  7. Dave Parker

    Dave Parker Inactive

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    What works for you, may not be the same as another photographer..

    I never throw anything away, it amazes me, how handy things come in, in future printing sessions...I keep them all in a file with notations about why they were not acceptable, which sparks my mind when something goes wrong again.

    Dave
     
  8. Jim Jones

    Jim Jones Subscriber

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    Longer lenses have some advantages, and one disadvantage for photographera with short arms.

    I rarely throw anything away. One never knows when an old print or piece of equipment will be useful. Obviously, I'm not married.
     
  9. Dave Parker

    Dave Parker Inactive

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    Whew wee!!! Jim I am married, but got smart and built a separate building to keep all of my mistakes in!

    LOL

    :D

    Dave
     
  10. Ole

    Ole Moderator Staff Member Moderator

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    I tried yesterday making 6x9" prints from 6x9cm negatives with a 110mm lens. Couldn't do it - the focus rail impacted the easel. So I switched to the 150mm lens, and had no problems.

    In that case it was not about coverage, image circle or anything else "optical". Merely working distance.
     
  11. tim rudman

    tim rudman Member

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    re lenses - its all been said

    Reject prints. I used to keep everything. Eventually when you run out of space (or rooms) you will have to reconsider.
    I recently redesigned & decorated my print room and in the process sorted and destroyed thousands of old and not so old prints carefully kept and serving no purpose. Looking at them I asked myself why on earth I kept them. Now I have space, am better organised and can kind things! Makes for a smoother calmer life!
    I still keep a lot of reject or early version prints but they now have to pass certain criteria as to why, otherwise they go into the 'learning bin'.
    The ones I keep are mostly for bleach or toning tests and timing before commiting the final versions, that is really useful and saves waste and disappointment. Also valuable for 'I wonder what happens if I do this' playtime sessions. I bin them after they have served their purpose (or so I tell myself).
    As a record? It is easier, more accessible in the future and much more efficient to keep the print progress trail details in written form (IMHO)
    Tim
     
  12. Matthew Gorringe

    Matthew Gorringe Member

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    I haven't tested this recently but you shouldn't be increasing the exposure time as long as you are comparing prints the same size. The reason light falls off with the square of distance is it's spread over a greater area. In this case the same light is spread over the same area, isn't it?

    I tend to keep reject prints for people who won't really notice the difference. It's good to be able to give people a print they like without having to give away one you know is the final print.
     
    Last edited by a moderator: Dec 8, 2006
  13. Steve Smith

    Steve Smith Member

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    It has indeed, so I will add one more thing!

    The traditional idea of a lens covering e.g. a 6x9 negative does not apply in the same sense here as the enlarger is really a camera in macro mode. As such, the coverage of a lens where the paper is the film and the negative is the object being photographed is larger than it would be in a normal camera sense.



    Steve.
     
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  15. matti

    matti Member

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    I have a big trash, a big box for unsatisfactory prints. A small box for ok prints. And a ring binder with ones I kind of like... I use the unsatisfactory prints to test toning etc on.

    /matti
     
  16. TheFlyingCamera

    TheFlyingCamera Membership Council Council

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    If you use a longer focal length lens, you have to back the enlarger head up farther to project the same size image. I'm inventing these numbers here for the sake of argument, but you'll see what I mean.

    If for example, to make an 8x10 enlargement from a 35mm negative, with a 50mm negative, you need to be 12" away from the baseboard, with an 80mm lens, you'd need to be 18" away. Thus the inverse square law comes into effect. You have to either open the lens aperture or increase the time to compensate for the increased distance.
     
  17. TheFlyingCamera

    TheFlyingCamera Membership Council Council

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    Steve- yes but.

    The but is that the enlarger lens is designed to cover a specific film format on its "front end" (ie the picture taking end). GOOD enlarger lenses have a 'coverage' angle on the taking end large enough to evenly illuminate and render the image of the negative, plus a little, even at full aperture. Cheap lenses will only minimally do so, and may even vignette and distort the corners at full aperture.
     
  18. Steve Smith

    Steve Smith Member

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    Yes, you're quite correct. I was trying to point out the error I used to make when I first started printing (using odd bits of inappropriate gear cobbled together) which was 'this lens on this camera covers this size of negative so it must be o.k. for that negative size if I use it on an enlarger'.

    Steve.
     
  19. Chan Tran

    Chan Tran Member

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    I throw all rejects away after getting the good prints. I work with 35mm and I use a 50mm lens for 8x10 and an 80mm lens for 4x5 prints. At low magnification the longer lens give me some more room. It's slower but then at low magnification it doesn't matter.
     
  20. TheFlyingCamera

    TheFlyingCamera Membership Council Council

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    That's actually a good point to remember - when making small prints (or even reduction prints in the case of large (4x5 and larger)) negatives, a longer lens gives you some back-off room to get in and do your burning/dodging thing, and also because it slows down the exposure time, it gives you enough time to actually do the burn/dodge. If your base exposure is 6 seconds @ minimum F-stop on your lens because the paper is only 2" from the front element of the lens, how are you going to burn/dodge the image???
     
  21. srs5694

    srs5694 Member

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    Another issue about lens focal length is that you won't get as great a resolution in the final print when using a given lens to enlarge a small negative to a specific size than when you use the same lens to enlarge a larger negative to the same size. For instance, when using an 80mm lens to make an 8x10 enlargement of a 35mm negative vs. a 6x6 negative, the 35mm negative can be thought of as a crop of the 6x6 negative, and you'll get resolution in the enlargement similar to what you'd get from a larger enlargement of the 6x6 negative -- roughly 15x18, if I've done the math right.

    Of course, the question was about using one lens vs. another, and that throws in the monkey wrench that the two lenses may have different resolution characteristics. If a given 80mm lens is sharper than a given 50mm lens, that fact may more than compensate for any loss of resolution from using the 80mm lens with a "too-small" format. Also, for some of the purposes that have already been mentioned, such as getting desirable additional head height when making small prints, the loss of resolution may not matter much.
     
  22. jstraw

    jstraw Member

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    I'm totally lost in that paragraph.

    I'm pretty sure that an 8x10 of a 35mm neg will have the same resolution no matter what focal length lens you use but I have no idea if you're saying that it will or will not.
     
  23. TheFlyingCamera

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    I'm not quite sure where you're coming from with this - of course the resolution of a smaller neg enlarged to a given size will be less on the final print than that of a larger negative. But this will happen regardless of the focal length of the enlarging lens being used. A 35mm neg enlarged to 8x10 with a 50mm lens will have the same resolution as a 35mm neg enlarged to 8x10 with an 80mm lens, but the resolution of the 8x10 print from a 2 1/4 neg using an 80mm lens will be sharper because the enlargement factor is less.

    To give you a situation, lets say that all film is capable of recording 500 lines of resolution per inch. A 35mm negative therefore has 500 horizontal lines (1 inch long on the short dimension). A 2 1/4 square negative has 1125 lines.

    Enlarge the 35mm neg to 8x10 - that's an 8x enlargement, so you end up with 62.5 lines per inch on the 8x10 print (500 divided by 8). By using the same lens to enlarge the 2 1/4 neg (to eliminate variation caused by different amounts of distortion, resolution loss, etc caused by the lens), we end up with a 4x enlargement, which means that the 2 1/4" neg puts 281.25 lines per inch on the 8x10 print. This is of course assuming that the taking lens on the 35mm camera was exactly the same as the taking lens on the 2 1/4" camera. 35mm taking lenses are known to have higher resolving power than 2 1/4" lenses - a 35mm lens is capable of resolving about 2x the resolution of a medium-format lens. So even if we adjust the curve to compensate for this, the 35mm is still producing 62 lines per inch, whereas the 2 1/4" is producing 141 lines per inch. This magnifies even further with large format film. Even when you control for the "normal" lens per each format, assuming the same is true with enlarging lenses as with taking lenses for a given format (not necessarily true in this case, but for the sake of argument we'll say it is), you're getting 62 lines for the 35mm neg, and 71 for the 2 1/4. The size wins, but it has nothing to do with the lens.
     
  24. srs5694

    srs5694 Member

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    Enlarging lenses have resolution characteristics, so the claim that "an 8x10 of a 35mm neg will have the same resolution no matter what focal length lens you use" is wrong -- the print's resolution will necessarily change when you change lenses. That was the point of my second paragraph, which you didn't quote.

    To rephrase my original point, imagine you've photographed a resolution chart with a magical camera lens and film that produce infinite resolution, and you're enlarging onto paper with infinite resolution; thus, any limitations you see in the print are due to the enlarging lens. You photograph the chart twice, once to fill the frame of your 6x6 camera and once to fill only a 24x36mm part of the negative. Your enlarging lens is a non-magical variety, so your enlargement will reveal limitations. You now make life-size prints of the original chart, which means you'll be enlarging more when you make the enlargement from the 24x36mm crop, which means the resulting print won't be as sharp. In other words, and stepping back to something more closely resembling the real world, using a longer focal length than necessary when making an enlargement means that you're not getting the lens's optimum sharpness. Whether that's better or worse than using a shorter lens, though, depends on the specific lens-to-lens comparison.
     
  25. Ole

    Ole Moderator Staff Member Moderator

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    This is just not correct, I'm afraid. You could say that a lens for a 35mm camera needs twice the resolution, but it doesn't happen in the real world.
     
  26. srs5694

    srs5694 Member

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    This makes logical sense to me; however, I just tested it experimentally and found that you do need to increase exposure time when using a larger lens -- or at least, that's what my color analyzer told me. (I didn't make any actual prints.) I got a recommended time of 4.5s with a 50mm lens at f/8 and a column height of 40cm. Replacing that lens with a 75mm lens at f/8 and a column neight of 55cm to match the print size (4x6 inches from a 35mm negative), the analyzer told me I'd need a 10s exposure. That's even a bit longer than what the inverse square law says would be needed, but I'm willing to chalk that up to measurement error, inaccuracies in one or both lenses' apertures, and differences in the light transmission through the two lenses' elements.