Rule of thumb at agencies for grain

[Diapositivo]

Hallo,
I am preparing myself to propose my images to some agencies. I shoot slides and scan them myself. I understand scans have to be very well made in order to satisfy the agencies market, which generally speaking tends to accepts only images that might be sold to a wide array of clients for a wide array of needs (so they must be technically OK under every respect).

While scanning and while photoretouching, I am continuously confronted with questions, as to which is the best course of action, to which I have no answers. There is a logical loop here: I would have to talk to agencies to know how to prepare my images, but before being able to talk with them I must show them my images, but before showing them I should talk to them... you get the point.

So I think asking these questions here would elicit answers from people who already know this market, and would probably be of general interest for anybody who wants to have a serious try at the stock agency market.

FIRST BIG DOUBT: noise reduction, noise levels

The problem is: how much noise is too much? And how little noise is too little?

As a rule of thumb, I set the image resolution to 300 ppi (which is the resolution generally requested by agencies), then view the image in Photoshop at "Print size", and then I just increase magnification a bit ("ctrl-+" one or two times).
If I cannot perceive noisiness at this level of magnification on screen, I suppose the image is OK.

This might prove to be a poor rule of thumb. Maybe the little remaining noise might result in a disturbing noise on print, if the printer (the machine) perceives the noise and tries to "reproduce" it on paper, it might make it worse (that probably depends on the printer and on the printing tecnique).
On the other hand, seeing the image at "print size" when the image is set at 300 ppi does not mean that I am seeing it at 300 ppi. The monitor being uncapable of such a resolution, it will scale the image and maybe "hide" the grain.

At "actual pixels" size the "grain" (which is not film grain but scanner noise) is always visible. I suppose this is true also for images obtained with DSLR. So I suppose agencies don't judge graininess by looking the image at actual pixel size.

So the question is:

Is there a rule of thumb to decide, by just looking at the image on the monitor, if an attempt of noise reduction is warranted? (Or: at what resolution should I check for noise on screen? Or: How do normally agencies judge the noisiness of an image?). I suppose there must be a rule of thumb such as: "graininess must be limited or absent at print size on the monitor" or "graniness should be limited or absent on the monitor at half print density, viewing the monitor at a distance equal to the monitor diagonal", or "observe the image at 75ppi and check graniness at 4 times the normal distance from the monitor" or something like that.


Thanks in advance for any help
Fabrizio

[Diapositivo]

Just to make my question clearer, I'll try to upload some pictures.
I feel I should not upload somewhere the high resolution image of a picture which I am going to propose to agencies, so I will post a low resolution JPEG and some crops.

The crops have been converted into JPEG but with the highest quality possible in PS, so the loss of quality is presumably minimal, I hope it makes some sense.

[attachment=3454:attachment]

The big JPEG shows much too obviously the entire frame. I applied noise reduction with NeatImage but no unsharp mask.

[attachment=3455:attachment]

The first crop, ritaglio_1.jpg, is a detail (actual pixel size) of the railing on top of the right tower.


[attachment=3456:attachment]

The second crop, ritaglio_2.jpg, is a detail (actual pixel size) of the lower three windows just above the gate.

My idea is that, although there is plenty of detail, when seen at actual pixel one might get an impression of softness.

Should I do anything?
Should I take away less noise?
Should I apply a very low amount of unsharp mask? (in general agencies insist they don't want unsharp mask to be applied, but some say a minimal amount is fine).

Thanks for any help
Fabrizio