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01-02-2019, 01:55 PM   #1
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Pentax Bellows and Slide Duplicator What am I doing wrong?

I have the Pentax Bellows and Duplicator, using a K10 with 55mm M42 lens with extension tube and getting pretty much full frame picture, BUT looking thru the view finder it appears dead on sharp, but when I take the picture and send it to Photoshop it is blurry and out of focus. What am I doing wrong? This is a picture that looked great when I shot it but the .jpg is out of focus,

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01-02-2019, 02:45 PM   #2
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Are you using the 2 second lockup or turning off Shake-Reduction?
01-02-2019, 03:13 PM   #3
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QuoteOriginally posted by jjbuzard Quote
but the .jpg is out of focus
Well, that's quite true! Although, there may be some (mostly sideways) motion blur, too.

I don't remember - does the K10 have live view? Try using that for focusing if you can. And, use the 2-second delay (was noted by Not a Number)

Also, the left side looks like it has significant spherical aberation (the image looks stretched out radially). Your lens may not have a very flat focus plane. Do you have a macro lens to try? Or a longer lens? Getting farther away from the slide may help with field flatness.
01-02-2019, 03:25 PM   #4
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Macro lenses are usually not ideal for slide duplication. The lenses are designed for a flat field whereas slides tend to bulge out from the center. Solutions are to use glass mount slides, at the risk of Newton Rings. Or stopping down for increased DOF.

The K10D does not have LV.

It's possible the focus calibration is off.

01-02-2019, 03:39 PM   #5
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You didn't mention the exposure you're using. If it's a short shutter speed that's forcing the lens near wide open, that would probably explain some of the "out-of-focus" portions you're seeing. You want to use a small (though not too small aperture) to gain sharpness in shooting slides. If vibration is well controlled, longer exposures are fine and you can get the aperture down to f8 - f11 which should improve sharpness, especially toward the edges.

You could try some focus bracketing to see if somehow you're missing the sweet spot for best focus. If you're going to be doing a lot of this, it might be best to see if you can lay your hands on an enlarger lens (like an El-Nikkor) which you can adapt to fit your bellows. Usually, a lens like the El-Nikkor will beat most other lenses for sharpness in this application. Again, you want to be stopped down to gain on sharpness and improve depth of field so center and edges are both in focus if there's any warping of the slide.

Keep in mind that since you're shooting 1:1, the indicated f-stop on the lens is not the effective f-stop. A 55mm lens will be working at an effective focal length of about 110mm for 1:1 and that doubles the f-stop from what is indicated by the lens (for a full-frame camera - the effective focal length will be less than a factor of 2 for crop frame shots since you won't be working at 1:1).

Last edited by Bob 256; 01-02-2019 at 03:47 PM.
01-02-2019, 04:41 PM   #6
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QuoteOriginally posted by jjbuzard Quote
BUT looking thru the view finder it appears dead on sharp, but when I take the picture and send it to Photoshop it is blurry and out of focus.
QuoteOriginally posted by Not a Number Quote
Are you using the 2 second lockup or turning off Shake-Reduction?
QuoteOriginally posted by Bob 256 Quote
You want to use a small (though not too small aperture) to gain sharpness in shooting slides.
Even looking through the viewfinder, you should be able to notice when the slide is this blurry. So I'm thinking the film in the slide holder moved when you took the picture (which happens a lot with mounted 35mm slides). Warping of the film is also very common, but with decent depth of field you should get most of the frame reasonably clear, unlike this photo where nothing appears clear.

Following the advice posted above by Not A Number and Bob 256 should help, a lot. My only advice is to have realistic expectations, high-resolution digital reproductions of small pieces of film will often reveal how "soft" the original photograph was. Think of it as getting that classic film look without having to do any extra work.
01-02-2019, 05:02 PM   #7
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What are you using for a light source? Using a flash set to manual will give consistant, repeatable output, which means there's one less thing to worry about once you've got the right exposure.
01-02-2019, 05:37 PM   #8
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QuoteOriginally posted by Not a Number Quote
Macro lenses are usually not ideal for slide duplication. The lenses are designed for a flat field whereas slides tend to bulge out from the center. Solutions are to use glass mount slides, at the risk of Newton Rings. Or stopping down for increased DOF.
Sorry to take things slightly off topic here, but I find this interesting. I can understand there may be distortion in slides, but I'd have thought a flat field lens was still better - just stopped down to allow increased depth of field (and hence allowing for the distortion). Am I wrong?

This is a genuine rather than rhetorical question. I've not done any slide reproduction work myself, but my assumption would have been to use a lens with the flattest possible field of focus...

01-02-2019, 08:01 PM   #9
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QuoteOriginally posted by Bob 256 Quote
You didn't mention the exposure you're using. If it's a short shutter speed that's forcing the lens near wide open, that would probably explain some of the "out-of-focus" portions you're seeing. You want to use a small (though not too small aperture) to gain sharpness in shooting slides. If vibration is well controlled, longer exposures are fine and you can get the aperture down to f8 - f11 which should improve sharpness, especially toward the edges.

You could try some focus bracketing to see if somehow you're missing the sweet spot for best focus. If you're going to be doing a lot of this, it might be best to see if you can lay your hands on an enlarger lens (like an El-Nikkor) which you can adapt to fit your bellows. Usually, a lens like the El-Nikkor will beat most other lenses for sharpness in this application. Again, you want to be stopped down to gain on sharpness and improve depth of field so center and edges are both in focus if there's any warping of the slide.

Keep in mind that since you're shooting 1:1, the indicated f-stop on the lens is not the effective f-stop. A 55mm lens will be working at an effective focal length of about 110mm for 1:1 and that doubles the f-stop from what is indicated by the lens (for a full-frame camera - the effective focal length will be less than a factor of 2 for crop frame shots since you won't be working at 1:1).
There is a link for EXIF data just above the posted image - indicates ss = 1/10th second, but does not include f-stop.

If the image looks sharp through the viewfinder, then I can think of only a few explanations:
1. motion blur
2. focus calibration is not accurate for this combination
3. dirty/damaged sensor
I assume the camera works normally without the bellows (?) which would rule out #3

To check #2 you could set up a scene with more front-to-back depth - lay a hair comb flat and shoot it lengthwise to see if there is anything in focus, even if the focus is not where you would expect it.

I can't think of anyway to prove that the problem is due to motion blur, but the solutions for preventing it have already been mentioned - faster shutter speed, solid setup (tripod, slide holder, etc), mirror lockup, use time delay or shutter release, etc. Also, be sure shake reduction is turned off for tripod shots.

Unlikely, but possible: maybe some kind of "special effects" filters have been accidently applied either in camera or when imported into Photoshop? Rule out by checking a RAW exposure.

As for the lens, I have read a dozen posts on several forums where people have used cheap zoom lenses to photograph slides, and the results were far better than this. Whatever the problem, I'm pretty sure it is not due to the lens, alone. Also, if the problem was a combination of film curvature and too shallow depth of field, that would be seen through the viewfinder, right?

---------- Post added 01-02-19 at 09:15 PM ----------

Final thought. Are you focusing with aperture wide open, then manually rotating the aperture to the correct f-stop before taking the exposure? Or does your rig automatically stop down at the time of exposure? Or are you trying to focus with the lens stopped down?
01-02-2019, 09:10 PM   #10
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QuoteOriginally posted by BigMackCam Quote
but my assumption would have been to use a lens with the flattest possible field of focus...
I have only done scanning of slides, but this makes sense to me. This is essentially a macro shot of a flat, very thin film that does warp somewhat, some of the time, but not in a predictable manner that can be deliberately compensated for by using a lens with the appropriate field curvature. Like any macro shot, depth of field is very small, but as long as the film is flat, DOF won't be less than the thickness of the film. The bellows and duplicator assembly should solidly fix the holder to the camera, so the only thing that can move is the slide itself (or if there are portions of the image that aren't blurred, then just the film inside its mount).

I now see that a small area of the right side of the tractor is relatively clear, but the centre and all the corners are very blurry. To me, that says the film was flexing while the shutter was open. If you have ever used a slide projector, you know that can happen. I think the only solution is to move the film back and forth in its mount with a lint-free, clean cloth and try taking the shot again, making sure shake reduction is off, aperture is f8 and the lens barrel isn't moved when stopping down the lens (nobody can manually focus through the viewfinder of an APS-C camera when the lens is stopped down to f8, so aperture will have to be adjusted between focusing and tripping the shutter).
01-02-2019, 09:47 PM   #11
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It looks like you took the picture with the lens wide open? There is some halo around the bright shirt that suggests it. And this would explain the out of focus peripheral areas as the slide is not flat. Also was there a hot light source near the film that would cause it to buckle? Anyway suggest you try lens at/about f/8, or maybe even f/11 (some loss due to diffraction is not so bad, and anyway you want to figure out what is happening. Once you sort things out a macro lens at about f/5.6 is likely ideal.)**

If flatness is still a problem you can take the film out of the slide holder and sandwich it between two thin glass slides, and there is a oil that can be applied to obtain optimum results. If you do this--glass and oil you likely need to do a search on best approach. There was an extended article on this in the magazine "camera techniques" well title may not be this but it is something like this.

_____
** A macro lens (flat field) is still best for copying, even if film is not flat. There was once a theory that an enlarger lens should not be flat field, and should have a curvature that sort of compensated for curvature of the negative, or the taking lens (don't recall which), and this was debunked long ago. It is essentially the same situation as here. Actually most symmetrical or close to symmetrical 50 mm (or close to 50 mm) relatively slow lenses (typically f/1.7 to f/2) should do pretty well if you don't have/don't buy a macro lens. (e.g., the Pentax 55mm f/1.8, 50 mm f/1.7, and 50 mm f/2, are likely pretty good--look at the lens optical layout--if about symmetrical then should be good).

---------- Post added 01-02-19 at 10:20 PM ----------

Possibly more reading than you want to invest in this, but you could read: " How to 'Scan' Film with a Camera—Well (Part 1)" and " ...Part 2)" by Ctein at The Online Photographer (Mike Johnston's blog). I did not read it, but in searching for camera technique article on the web, I found Ctein's article. (I like MIke Johnston's site BTW, it is one of three I give money to, the other two are this one [PF] and KenRockwell--as these three provide me much useful information so I return the favour.)

Last edited by dms; 01-02-2019 at 10:24 PM.
01-02-2019, 10:35 PM   #12
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QuoteOriginally posted by BigMackCam Quote
Sorry to take things slightly off topic here, but I find this interesting. I can understand there may be distortion in slides, but I'd have thought a flat field lens was still better - just stopped down to allow increased depth of field (and hence allowing for the distortion). Am I wrong?

This is a genuine rather than rhetorical question. I've not done any slide reproduction work myself, but my assumption would have been to use a lens with the flattest possible field of focus...
I'm old school. From all the classes, books and articles from Modern/Popular Photography I took or read in the 80's all said a normal prime lens was more desirable for slide copying because of the curvature of the film chip in cardboard or plastic mounts. A macro lens was said to work best for slides in glass mounts which press the chip flat.
01-02-2019, 11:13 PM   #13
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QuoteOriginally posted by Not a Number Quote
I'm old school. From all the classes, books and articles from Modern/Popular Photography I took or read in the 80's all said a normal prime lens was more desirable for slide copying because of the curvature of the film chip in cardboard or plastic mounts. A macro lens was said to work best for slides in glass mounts which press the chip flat.
If this was true, and the slide curvature and lens curvature were opposite then the tolerance would be even worse. Since you cannot (as a simple practical matter) characterize the film and lens curvature, the best you can do is minimize the error by taking a lens that is flat field, anything else is almost certain to be worse. Of course there is a statistical chance it may be better, but that's like saying a TC optics may improve the primary lens resolution (that the TC is attached to)--it is possible but it never happens, unless by careful design (as the correction lenses added to the Hubble telescope).
01-03-2019, 01:25 AM   #14
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I know nothing about shooting slides, but do a fair bit of macro shooting with bellows, my pentax bellows has a small button / knob, that has to be pressed in for the lens To be stopped down, regardless of the aperture ring being set to whatever value I want, if the button is out, then you're shooting wide open.
It takes a press in and a little turn to keep the button closed, then you can shoot at whatever aperture you wish to set.
01-03-2019, 06:45 AM   #15
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QuoteOriginally posted by AstroDave Quote
Or a longer lens?

A longer lens will not work = it will not be possible to position the lens & slide to get the latter in focus.
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