At what f/ stop does your lens perform the best?

[Lizziejane]

I found this link in another board and found it interesting.

Couple of things to keep in mind - not all lens have been tested. Those that have been are clearly labeled as tested. On the "blur index" chart, the lower the number, the better. You can adjust the f/ stop and focal length on zoom lens charts. There are other charts for chromatic abberation, vignetting, and distortion, and one of these, I'm gonna learn what all that actually means!

http://www.slrgear.com/reviews/showcat.php/cat/2

 

[Marinerbaby]

I believe if I am reading the tesing right it is best at f/4 but I can get tack sharp wide open too. I do portrait though so I am more concerned about the subject (eyes/face) than anything else.

I just have to be careful not to only get one eye in focus at f/1.2.

Thanks for posting this. It was very interesting.

 

[Lizziejane]

I just have to be careful not to only get one eye in focus at f/1.2.

Thanks for posting this. It was very interesting.

This is my problem constantly. I have a 50mm prime, and if I "fill the frame" like I keep reading, at f/1.8 I get only part of the face in sharp focus. Would I be better off to back up and not fill the frame and crop the photo - isn't DOF affected by how close you are? I'm getting so discouraged at the number of crappy photos I"m ending up with!

 

[handicap18]

This is my problem constantly. I have a 50mm prime, and if I "fill the frame" like I keep reading, at f/1.8 I get only part of the face in sharp focus. Would I be better off to back up and not fill the frame and crop the photo - isn't DOF affected by how close you are? I'm getting so discouraged at the number of crappy photos I"m ending up with!

f/1.8 is going to give you VERY little DOF if any at all. And yes the closer you get the less DOF you'll get on the subject. Backing off will help and stopping down will as well. You might have to get more light to be able to stop down to about f/4. The only way both eyes will be in focus at f/1.8 will be if they are the same distance from you. If the person is angled at all or your angled then only 1 will be in foucs.

As for the topic at hand, without reading the reviews at the site posted, I would say that both my primes were sharpest between f/4 and f/8 or so (article says f/4 and f/11, but are still quite sharp right though). For my zooms I would say f/5.6 - f/11, but would lose some sharpness the closer to the far end of the zoom which is typical of most zoom lenses. This is pretty much what the reviews say too.

 

[Groucho]

Isn't that what MTF charts are supposed to tell you?

I'm really looking forward to my next DSLR (cough, cough), which has an MTF program line, which will automatically try to use the sharpest aperture for a given lens, since not all lenses are the same. I wouldn't be surprised to see this become a more common feature on DSLRs in the next couple product cycles.

 

[Marinerbaby]

This is my problem constantly. I have a 50mm prime, and if I "fill the frame" like I keep reading, at f/1.8 I get only part of the face in sharp focus. Would I be better off to back up and not fill the frame and crop the photo - isn't DOF affected by how close you are? I'm getting so discouraged at the number of crappy photos I"m ending up with!

I have the 85 1.2 prime and I find it challenging wide open sometimes. I usually try and back up a bit (I can crop it down in PS) so that the face and eyes stay in focus. I do love the look though and in low light it's great.

 

[Lizziejane]

and a close up shot...

May I ask what f/ stop this was at, and how far were you from the subject? Beautiful shot!

 

[MarkBarbieri]

Isn't that what MTF charts are supposed to tell you?

Yes and no. MTF charts don't cover chromatic aberation, linear distortion, or vignetting. The other problem with MTF's (at least Canon's, I'm not sure about anyone elses) is that they are theoretical rather than measured. It is also not possible to compare MTF charts between makers because their techniques differ.

It's pretty interesting, but there are several problems. First, few lenses are covered. Even some very popular lenses have not been tested. Second, they are testing full frame lenses on cropped bodies. Now that might make sense for manufacturers without full frame sensors, but to test something like the Canon 16-35 on a 1.6x sensor is rather limiting.

These tests also leave out a host of other differentiating characteristics between lenses, including resolution, resistance to flare, contrast, stabilization effectiveness, focus speed, focus accuracy, and bokeh. They are a nice starting place, but they don't tell the whole story.

There were some surprising results in the tests that I looked at. Canon's 50mm f/1.2 didn't do well at all compared to it's initial reviews. Perhaps the reviewers were comparing it to the old f/1.0. While it was an engineering marvel and corporate bragging tool, it was a pretty bad lens.

Comparing the Canon and Nikon kit lenses was interesting. The Canon was definitely the loser at the wide end but actually outperformed the Nikon at the long end. The overall nod still goes to the Nikon, but the difference was not as pronounced as you'd think from the reputation of the Canon kit lens here.

It's interesting to see the number of lenses reviewed for each maker:

Canon 702
Minolta 15
Nikon 533
Olympus 40
Panasonic 1
Pentax 41
Samsung 0
Sigma 281
Sony 5
Tamron 119
Tokina 45
Vivitar 6

 

[jann1033]

This is my problem constantly. I have a 50mm prime, and if I "fill the frame" like I keep reading, at f/1.8 I get only part of the face in sharp focus. Would I be better off to back up and not fill the frame and crop the photo - isn't DOF affected by how close you are? I'm getting so discouraged at the number of crappy photos I"m ending up with!

that lens is my nemesis
i thought it was just me since nothing i took ever turned out with that lens, then took a bunch of photos with it that turned out fine... figured it was me although i couldn't for the life of me tell what i was doing differently. took a bunch more a few days later... turned out horrendous...
tried all apertures etc since i was figuring i had been somehow messing up with the lens. i have no problem what so ever with my 100 prime, even ones i took on the same day of the same subjects as the lousy 50mm ones...i have no idea why this lens and i do not get along. i thought maybe i was not at the right distance but no way i could move enough to get it to change how much is in the frame and have it focus.... i tried focus tests some seemed off, a few days later were fine...it is my " great white whale" for sure as i am determined to figure out what is up with me and this lens

 

[Marinerbaby]

May I ask what f/ stop this was at, and how far were you from the subject? Beautiful shot!

Thank you. It was shot wide open at f/1.2, ISO 200, SS 1250. I don't remember how far back I was from the subject. I was moving around quiet a bit with a moving two year old but it was cropped some looking at the original file.

 

[boBQuincy]

Comparing the Canon and Nikon kit lenses was interesting. The Canon was definitely the loser at the wide end but actually outperformed the Nikon at the long end. The overall nod still goes to the Nikon, but the difference was not as pronounced as you'd think from the reputation of the Canon kit lens here.

Canon's 18-55 gets a lot of unfair treatment from what I see. One Canon forum even has a thread "show me your kit lens images", many of them are really good and quite sharp.
My theory is that many of those with the kit lens are new to SLRs and are blaming a lot of their newbie errors on the inexpensive lens. We have some better lenses and rarely use our 18-55 but it seems to work very well, just don't expect a lot when it is wide open.

ps, we also have one of Canon's low end 28-90 lenses, also no paragon of goodness, and it has turned out some really good images.

 

[Lizziejane]

that lens is my nemesis
i thought it was just me since nothing i took ever turned out with that lens, then took a bunch of photos with it that turned out fine... figured it was me although i couldn't for the life of me tell what i was doing differently. took a bunch more a few days later... turned out horrendous...
tried all apertures etc since i was figuring i had been somehow messing up with the lens. i have no problem what so ever with my 100 prime, even ones i took on the same day of the same subjects as the lousy 50mm ones...i have no idea why this lens and i do not get along. i thought maybe i was not at the right distance but no way i could move enough to get it to change how much is in the frame and have it focus.... i tried focus tests some seemed off, a few days later were fine...it is my " great white whale" for sure as i am determined to figure out what is up with me and this lens

Jann, if you figure it out, please let me know! I'm assuming the answer has to be distance to subject at f/1.8, but I can't seem to figure out what that is

 

[ukcatfan]

Canon's 18-55 gets a lot of unfair treatment from what I see. One Canon forum even has a thread "show me your kit lens images", many of them are really good and quite sharp.
My theory is that many of those with the kit lens are new to SLRs and are blaming a lot of their newbie errors on the inexpensive lens. We have some better lenses and rarely use our 18-55 but it seems to work very well, just don't expect a lot when it is wide open.

ps, we also have one of Canon's low end 28-90 lenses, also no paragon of goodness, and it has turned out some really good images.

IMO it is all a perspective situation. I would bet that some of the worst DSLR lenses still do better than a p&s when used correctly. My biggest gripes with the Canon kit are build related instead of IQ related. When stopped down, I bet you could take the same shot from each manufacturer's kit lens and there would be almost no difference in the image.

Kevin

 

[boBQuincy]

IMO it is all a perspective situation. I would bet that some of the worst DSLR lenses still do better than a p&s when used correctly. My biggest gripes with the Canon kit are build related instead of IQ related. When stopped down, I bet you could take the same shot from each manufacturer's kit lens and there would be almost no difference in the image.

Kevin

Build quality may not be a big issue with the inexpensive lenses but the perception sure is. Even though I have never had a problem they all feel like they will break just by looking at them.
It's not easy to get that, no matter how much you spend you just can't buy the feel of cheapness!

 

[jann1033]

Build quality may not be a big issue with the inexpensive lenses but the perception sure is. Even though I have never had a problem they all feel like they will break just by looking at them.
It's not easy to get that, no matter how much you spend you just can't buy the feel of cheapness!

that's the main thing i couldn't overcome with the 70-300 is comparing it to the 70-200 f4, the 300 felt like a $100 lens and my won out even though i know in my head it's a great lens (& cost almost $100 less than the other great lens i got)

that is something i would like to see different in reviews such as these.. while imo the build quality is important, it's not as important to me when i am first looking for a lens so i wish they wouldn't average it in with the actual things that make the photo sharp or not etc.. that way you could just go to the 9s or whatever , this way you have to read every review to see what makes it less than stellar. like i think the rated the 50 f1.8 7+ something when after you read the review one of the very few things they didn't praise/rate close to the $$$ ones was the build.

i saw that 18-55 site as well and kind of have to laugh when i hear the kit lens gripped about...at least i admit i don't know what i'm doing

one question about the charts though when they say "average" vs whatever lens they are testing ( ie comparing ca) so they mean average for all lenses or for lenses in that same category (ie ultra wide)?

 

[Groucho]

Looking at this link again... am I missing something?

I don't see any scientific tests or anything here. All I see is a big list of lenses (with incomplete information - they don't know how many blades are in a Pentax 50mm?) and there are user reviews. How is this any different than looking at comments at Amazon, Adorama, B&H, etc? There's no indication that any of the comments is from someone who has sampled competing lenses - for example, someone going from a PnS to their first DSLR will certainly give most any kit lens a glowing review.

...OK, before I hit "post", I see that there are a few that actually have some tests done. I looked at several (inc. Canon and Nikon) and saw nothing for any of them until I looked at the main page and saw some info there.

This page shows only the lenses they've tested. They are all Canon or Nikon mount except for the two lonely Olympus lenses that come as a kit with the E500. This should probably go a ways towards explaining the lack of response from non-C/N shooters.