Out of Focus areas on print

[Carlsen Highway]

I have in my hand some prints made this evening. The centre is pin sharp, but around the edges "fading" out of focus. Enough to be noticable.

In your experience does this sound like:

Thi sis over several different prints and all exhibit the same thing - but not exactly the same - some have the left side more in focus than others do for example.

A - enlarger lens is at fault.
B - the paper itself is not sitting flat (but then the middle would be OOF focus more likely?) I have the paper in a frame...but perhaps maybe a sheet of glass may be in order?
C - or maybe the negative is not held flat in the carrier?

I cant get back in till Tuesday next week, so I cant experiment. Just thought some others may have dealth with something similiar.

 

[sevo]

Enlarger lens (did you forget to stop down?). Or the negative is not flat in the holder. It can't be the paper - the DOF at the paper is big enough to cover anything short of a obvious bulge, and besides you will have focused on the empty frame, so that a bulge would move the centre rather than the edges (where the paper is held down by the frame) out of the on-frame focus.

Another reason might be a mis-assembled condenser - though I'd expect focus faults to be secondary to vignetting there.

 

[ChrisN]

I'd guess probably not the lens. I'd guess at the negative not being held flat as the most likely cause. The effect varies - some worse than others? Probably not lens or enlarger alignment, which would give a consistent result. So either the negative or the paper is moving.

What sort of enlarger? In today's post I received a piece of anti-newton ring glass to put on top of the negatives in the holder for my LPL 7700 - it has the neg sandwiched between two sheets of glass. That keeps it flat but I have to get the dust off four surfaces!

You're not using the lens wide open, are you? I gather that most enlarger lenses need to be stopped down at least two stops to achieve their optimum performance. If you use a grain focuser you can check the focus at different apertures, and also at the centre and the edges.

I found instructions recently to make a simple vacuum easel with a pine frame and pegboard, hooked up to the vacuum cleaner. That might be worth a try, but probably more necessary for big paper sizes than 8x10.

Good luck!

 

[oftheherd]

There was another thread on oof areas of a print not too long ago. That time it was the negative getting too hot. This can be because you leave the enlarger on too long, such as for focusing, or the exposure (too small an f/stop), or there is no heat protection, or all the above. That may not be your problem, but it should be checked.

 

[sepiareverb]

Enlarger is could be out of alignment. Film plane, lens plane and baseboard all need to be parallel to have sharp prints. This is most often simply side to side OR front to back OOF, rarely both unless the enlarger has been roughly moved.

 

[Pickett Wilson]

It sounds like you are using the lens wide open. Or using a really lousy lens.

 

[tbm]

I had something similar to your occurence happen to me the other day, and I discovered that the blurring was caused by printing exposure timings of 25-35 seconds which heated the negative. Once I had opened the lens and thus reduced the exposure timings down, the blurring no longer occurred.

 

[ZeissFan]

Some enlargers had a piece of heat-absorbing glass to reduce negative "pop," as I remember it being called way back when.

If the negative is blurry on one side, that might indicate that the lens board isn't parallel to the base.

If you could scan the print or take a digital photo of it, that would help. Your description isn't detailed enough to make an accurate diagnosis.

Also, if you have a grain enlarger, you could check that yourself. Check focus in the middle and then move the grain enlarger to the edge of the photo and check again.

Check the sides and all four corners.