macro

You misunderstood all my questions. You also misunderstood all my statements, though I cannot make them any clearer.

Diffraction is a law of physics and reduces the quality of any image shot stopped down enough. Posting one image you think is "good enough" in no way disproves that. By the way, it is an OK image, I am sure suitable to the task, but far from the best lens shot I have ever seen.

Look at any MTF test on, say photozone.de. Read any document on diffraction. We are not just making this stuff up!

I just take a picture and look at an A4 print and say is that sharp enough and it usually is

Can somebody please tell me what is wrong with that picture of the Vivitar lens? Would you not be happy if you could take a picture like that?

Theory and lines per mm are OK but hardly any of it ever reaches the final print.

When I first got my Pentax A 50mm f/1.7 with a new Super A I tested it against a Patterson Reslution Chart which went up to 120 lpmm and it was off the chart at f/8. So I did the test again increasing the distance by 25% and it seemed that the lens was good for 140 lpmm which I thought was great.

I then got curious about how many of them lpmm actually finished up on a 10x8 sheet of BW glossy fibre based paper after trying with about 6 top 50mm enlarger lenses and a Nikon 63mm (top lens according to BJP) the most I could manage was 90 lpmm on the paper and that was with an Omicron 50mm f/2.8 EL (top lens according to AP).

In fact if you use a 20x magnifier on a 35mm negative you can see stuff that isn't on and never will be on a print, so don't think that laboratory measurements mean anything outside the lab. If it works.... just use it.... it will be alright, I won't tell anybody you used f/22

ok cALM dOWN!! bE cOOL!!

I don't know if people are being argumentative or just don't understand what I said.

Good job I didn't post a photo taken by candlelight on DAYLIGHT balanced film. People would be jumping on me with all kinds of lab reports and statements from Kodak saying it's incorrect and you can't do it. Photography has always broken rules, we put stuff in front of our lenses when it reduces resolution etc.

It was obviously/probably a bit difficult, because there was only one photograph, for some of you to understand what I was saying, so here's a test photograph taken on the left at f/11 and on the right at f/22. These are staight Jpegs off the camera with no PP captured by the print screen button. The captured view was at 100% (1:1) So they are the actual pixels.

I hope you can see that the right is sharper than the left and there is no problem at all using f/22 and when I want maximum sharpness I will continue to do so, without even consulting a technical manual




This was the full test shot

I was demonstrating the effects of aperture recently to an audience of around 70 photographers and how changing aperture affects sharpness.

And it does. A lens will peak in terms of quality at the middle apertures, often around f8 but maybe at around f5.6 for faster lenses or f11 for older designs.

Lens sharpness does fall off towards f22, although DOF obviously increases, so these two factors need to be weighed against each other.

The better the lens the more the effect will be noticed. If you get a poor lens, usually a cheap older zoom, then it is possible that sharpness will peak at f16 or f22, but this is because the overall performance is not very good anyway.

For optimum quality, provided there is enough DOF, I would tend to use f8 or f11. Once we get to f16 the results of diffraction are becoming visible and by f22 definitely so. This is why many older lenses only go to f16.

What you've said there is correct John and unfortunately this thread has drifted well away from my compliment on an excellent sharp photo of a Vivitar lens done by a very good photographer who knew his equipment well and what he was doing with it. He should make a video of his technique and stick it on youtube

A good photographer knows that if he's copying a flat chart he needs to use the sharpest aperture of his lens approx. f/8-f/11

If he was photographing a 3D object say a lens or camera body and he wanted as much of it sharp as possible he would realize that compromises have to be made and he would know how far he can push his equipment. He will know that as he stops down certain aberrations get worse whilst other things such as DOF get better and peripheral aberration is reduced.

This is three shots I've just done in the kitchen using flash combined.

No PP whatsoever grab using print screen from the viewer.
100% Crops. Distance 1.4M Lens at 55mm, ISO = 100

Pentax 55-300mm at f/11 - f/16 - f/22 (left to right)




If I wanted as much sharp as possible I wouldn't hesitate to use the last shot at f/22 (i.e. shot on right).

The shot at the lenses optimum sharpness f/11 would be classed as unacceptable.

The shot in the middle at f/16 is usable and was actually the correct exposure for the flashgun.

The f/22 shot is actually a bit underexposed due to the flashgun being underpower by 1 stop.

Algernon, I don't get it. What have you focused on in the first image? It looks like nothing is in focus, so yeah, it's pretty soft.

If anything the Tamron actually has the edge over the Pentax wide open - the Pentax then has a similarly small advantage stopped down.

If you had circumstances like that with two lenses, then you have a choice. Depending on what you wanted to use a lens for you can match performance to requirements.

So in the example given, a macro lens that was superior when stopped down would generally be an advantage. Most macro shots need as much DOF as we can get, so stopping down is the norm.

A telephoto lens where distant shots at open aperture were the aim might well have an advantage if it were razor sharp wide open. If it was a portrait lens, then most subjects would not appreciate the razor sharp rendering of all their facial defects...

That's why I think it's a great pity that manufacturers don't tell us up front what the characteristics of their lenses are. If they did we could make more informed choices.

I agree, it's ridiculous. Full MTF and other specs should be made available on all lenses. The manufacturers have this info but do not release it. I think only Leica act professionally in this regard.