Sharpness of negatives

[Leigh]

... and use movements to place your focus plane.

I would STRONGLY advise against that approach. You're introducing a whole new variable into the process.

There are already too many variables floating around.

- Leigh

[Jack the boatman]

Hello,

Thanks to everyone who has commented. You have given me food for thought and I will try out your suggestions.

In answer to some of the comments:

The ground glass is pointing towards the lens. The camera was new when I bought it.

I like the steel tape idea.

Assessing sharpness. I haven't printed any of my negatives because when seen on a 17 inch monitor the results are poorer than I want. I don't think anyone who sees the results I am talking about would disagree.

I am comparing with a Nikon d60 digital camera with 18-135mm zoom lens. I have taken results from this camera at f32 and the result is MUCH sharper than my 5 x 4. This is even after the digital image has been blown up to a greater magnification.

Aerial image. I didn't realise this could be done. I will try it.

Diffraction. I considered this, but again from the comparison with my digital images, I would have expected the digital image at f32 to suffer more than the 5 x 4 at f32. Am I right in assuming this. My understanding (very rusty) of the physics involved is that light will be bent whenever it passes a barrier. Because f32 on APCS is a much smaller absolute diameter than f32 on my 5 x 4, would diffraction not be more likely on the digital image?

Thanks again for your comments

Jack

[Bruce Watson]

Assessing sharpness. I haven't printed any of my negatives because when seen on a 17 inch monitor the results are poorer than I want. I don't think anyone who sees the results I am talking about would disagree.

You might well be surprised.

You can't judge the sharpness of a final print by looking at a computer monitor. If you want to know what the final print will look like, you have to make a print. If you are looking at actual pixels in Photoshop with a 72ppi monitor, and you're talking about making a print at 360ppi, the monitor is showing you a 360/72=5x magnification!

I'm just sayin' that a soft image in a computer monitor is normal.

That said, LF ain't easy. This ain't no point-'n-shoot. LF rewards accuracy and precision. Most LFers go through a fair amount of film and prints to become fluent in the medium. Patience and practice, lots of practice, are your friends.

[E. von Hoegh]

Hello,

Thanks to everyone who has commented. You have given me food for thought and I will try out your suggestions.

In answer to some of the comments:

The ground glass is pointing towards the lens. The camera was new when I bought it.

I like the steel tape idea.

Assessing sharpness. I haven't printed any of my negatives because when seen on a 17 inch monitor the results are poorer than I want. I don't think anyone who sees the results I am talking about would disagree.

I am comparing with a Nikon d60 digital camera with 18-135mm zoom lens. I have taken results from this camera at f32 and the result is MUCH sharper than my 5 x 4. This is even after the digital image has been blown up to a greater magnification.

Aerial image. I didn't realise this could be done. I will try it.

Diffraction. I considered this, but again from the comparison with my digital images, I would have expected the digital image at f32 to suffer more than the 5 x 4 at f32. Am I right in assuming this. My understanding (very rusty) of the physics involved is that light will be bent whenever it passes a barrier. Because f32 on APCS is a much smaller absolute diameter than f32 on my 5 x 4, would diffraction not be more likely on the digital image?

Thanks again for your comments

Jack

The diffraction limit at f:32 is independent of focal length. However, the aberrations will scale with focal length assuming the same lens design. While you are almost certainly into diffraction at f:32, meaning that diffraction is limiting resolution rather than aberrations, the limit at f;32 is still roughly 50 lp/mm. Try using the lenses at f;11. Forget viewing the scans of the negs on a monitor, it's not a useful asessment of sharpness. Too many links in that chain.

[Dennis]

My lenses certainly aren't fuzzy at f32. That's my favorite f stop and I am a sharpness freak. I wouldn't expect it on a new camera but on both my 4x5 and 8x10 I have to be very careful that putting in a film holder doesn't make the back move a tiny bit. I keep a shim with my 4x5 to disallow movement and often put a light stand up under the back on my 8x10 to prevent any sort of sag.
Dennis

[chuck94022]

I would STRONGLY advise against that approach. You're introducing a whole new variable into the process.

There are already too many variables floating around.

- Leigh

I should have been more clear. I meant to do that in the field, not for a lens test!

[chuck94022]

Hello,
...

I am comparing with a Nikon d60 digital camera with 18-135mm zoom lens. I have taken results from this camera at f32 and the result is MUCH sharper than my 5 x 4. This is even after the digital image has been blown up to a greater magnification.

...

Diffraction. I considered this, but again from the comparison with my digital images, I would have expected the digital image at f32 to suffer more than the 5 x 4 at f32. Am I right in assuming this. My understanding (very rusty) of the physics involved is that light will be bent whenever it passes a barrier. Because f32 on APCS is a much smaller absolute diameter than f32 on my 5 x 4, would diffraction not be more likely on the digital image?

Thanks again for your comments

Jack

Well for one thing, the D60 sensor is taking discrete samples of the light and providing a pixelated interpretation of what it detected. A D60 will thus mask a lot of diffraction and appear sharp, while not rendering detail as fine as film can. So I am not surprised by your D60 observation.

I still maintain that you are not operating in the sharpest region of your lens, and film is very unforgiving in this regard as an analog recording medium.

Frankly I think we are all groping in the dark here. All we have is your subjective observation of a negative. And here we are telling you to tear your camera apart and check the ground glass! ;-) (I'm exaggerating...) I have no idea if what you are seeing is normal or not. But best of luck!

[E. von Hoegh]

Well for one thing, the D60 sensor is taking discrete samples of the light and providing a pixelated interpretation of what it detected. A D60 will thus mask a lot of diffraction and appear sharp, while not rendering detail as fine as film can. So I am not surprised by your D60 observation.

I still maintain that you are not operating in the sharpest region of your lens, and film is very unforgiving in this regard as an analog recording medium.

Frankly I think we are all groping in the dark here. All we have is your subjective observation of a negative. And here we are telling you to tear your camera apart and check the ground glass! ;-) (I'm exaggerating...) I have no idea if what you are seeing is normal or not. But best of luck!

Tear the camera apart? hardly. You just remove the back. Checking for proper istallation of the GG when one is having trouble focussing is a bit like checking for gas in the tank when the car cranks but won't start.

[chuck94022]

Assessing sharpness. I haven't printed any of my negatives because when seen on a 17 inch monitor the results are poorer than I want. I don't think anyone who sees the results I am talking about would disagree.

You said before you were assessing through a loupe. Here you say you are assessing on a 17 inch monitor. If that is the case I assume you are scanning. Have you assessed your scanner? All but the highest quality scans require a bit of sharpening, in my experience.

[SergeiR]

Diffraction. I considered this, but again from the comparison with my digital images, I would have expected the digital image at f32 to suffer more than the 5 x 4 at f32. Am I right in assuming this. My understanding (very rusty) of the physics involved is that light will be bent whenever it passes a barrier. Because f32 on APCS is a much smaller absolute diameter than f32 on my 5 x 4, would diffraction not be more likely on the digital image?

APSC peaks at about f5.6 (FF on f8 , 4/3 at about f4). Past that - diffraction. Plus you got digital vs film (includes questions on processing, alignment & etc).
So you comparing oranges and ducks. Different species entirely.

So, since you now can check your images on 17" monitor (scanned? what scanner, what mounting technique used) - show them to forum, and collective mind would be able to say something, instead of guessing.