Is ?

[jann1033]

ok what am i missing
just out of boredom and cause i have used the lens 1 time since i bought it i tried out my phoenix 100 f3.5 macro lens ( $140) as just a 100mm( no macro) and compared it to my canon 28-135 IS 3.5-5.6 ($400)

at 250/f3.5 the 100mm was much much sharper ,at 160/5.0 much sharper and at 1/80 5.6 noticeably sharper than the canon at 1/80 5.6 so is it because even a cheap prime is better than a moderate zoom ? wouldn't it seem with the IS that would have somehow come into play so the canon would have been sharper?
canon

phoenix

anticipating i could easily mix them up i include the window frame in the phoenix so i am positive they are the right lens per picture

 

[ukcatfan]

I have heard that just about any prime will be sharper than any zoom when you are not talking about pro glass. If you like the results, you should start using it more.

Also, you should be able to find the lens used in your EXIF data of each file. I have a Pentax, not Canon, but I am sure that if they put it in there then Canon would also.

Kevin

 

[DVC Jen]

OK I may be TOTALLY wrong here - but I just spent about 3 hours reading my "Digital Photography" book that I got for Christmas as well as playing around with that I learned in the book on my own Canon XTi.

Am I wrong in my thinking that you may get a sharper picture using f/22 1/20?

Did you zoom in too close for that aperature and shutter speed to work for you?

The book said that for great depth of field to use a higher aperature. I am sure however that YOU already know all this.

I, on the other hand, am still trying to learn all there is - and I know I have a long way to go.

I guess I am just wondering and trying to understand why you used the aperature you did?

 

[ukcatfan]

Am I wrong in my thinking that you may get a sharper picture using f/22 1/20?

Every lens is different, but in general I believe that the sharpest aperture on a lens is supposed to be around 3 stops from the widest. On these f/3.5 lenses, that would be between F/8 and F/11 if my math is correct. If I am correct, then F/22 would not be sharper. I believe that you can think of the sharpness across the aperture range in terms of a bell curve that is shifted a little off center towards the wide side of the range. Can anyone more advanced give some more details?

Kevin

 

[jann1033]

i used the same mm, same f stop etc for both lens, mainly to see how they compared, not really to see where the lens was sharpest. i was considering how they would be for inside (aquarium) pictures which is why i wanted the lowest light possible. the largest aperture on the 100mm is 3.5 and so naturally since i could get it to 250, it was sharper than anything at that mm i could get with the canon, f5.0-5.6 at around 80mm on up...the 80 f5.6 is the fastest i could get with the canon,taking it inside to the outside figuring that would be the closest to what i would be using it for at an aquarium, darker to brighter.

so am i right in thinking the following....
this is making me think more and more i want a larger aperture for my next zoom...( love the 70-200 f2.8 but it was way over budget so thinking i might get the 70-200 f4 if i can( see my tripod thread )...the 70-300 IS is 4.0( or 4.5 i can never remember) at 70 but would be 5.6 at 200-300 which is the end i want it for more,
which was why when i saw this i wondered how much the IS would come into play to make up for the smaller aperture if at all.( not for light but for sharpness, thinking the supposed 3 stops in shutter speed(?) so in this case, it isn't going to help me any in lower light, higher zoom really, the widest i could get would still be 80 at 5.6, it's just it would hopefully be as sharp at a few slower shutter speeds than 80, right????? or wrong? if wrong please explain where my brain is missing some synapse

 

[DVC Jen]

my brain is so saturated from all of the "studying" I have been doing this past week. I could very well have confused sharpness for depth of field.

I dunno - sometimes I wonder if all this is nothing more than a shot in the dark and if so - no wonder I am so confused.

 

[boBQuincy]

Here's my take on it:

most primes are sharp, even the inexpensive Canon 50 f/1.8 is very sharp.

The 100 was stopped down, close to it's best aperture while the zoom was wide open. Stop the zoom down two stops and it probably improves quite a lot.

There is a lot going on in the scene, it is possible the lenses did not both focus in the same spot. The zoom appears to be sharper in the closer range than in the large piece of branch. I have found that some of my lenses won't even focus in the same spot twice in a row with this much in the scene.

I use my 70-200 f/4 handheld when I have no other options, it's ok at fast shutter speeds but a roll of the dice below 1/250. Take three photos in a row, one should be decent!

 

[MarkBarbieri]

I'm with boBQuincy. I think you are seeing focus differences. Try taking a picture of something with fine detail that is flat so that focus and DOF issues don't come into play. A box of cereal might work well. Another option would be to take a photo of something so far away that DOF isn't an issue.

If you want to be really careful about it, use a tripod, mirror lock-up, and a remote shutter release. Just be sure that you turn off the IS on the 28-135mm if you put it on a tripod.

 

[jann1033]

both lenses are f3.5-5.6, the difference naturally being the 100mm on the canon is no larger than 5.6, the other one naturally 3.5-5.6 at 100 so i don't understand what you mean about the stops, ie wouldn't they both be wide open? which i know isn't the sharpest range but not seeing how that would be different between the lenses...i took about 20 photos in all but all the canon was less sharp( compared them blown up side by side, same place in the photo, these were just the only 2 i converted to jpg so i could put them on photobucket. i understand about maybe focusing at a different place and had this been a scientific research project in stead of an i wonder if this would work tomorrow deal, next time I'll try something flatter....it was more just a curiosity to me that the cheaper prime was sharper the whole way across the board at the same focal length than the canon especially given my shaky hands that evidently can't be blamed nearly as much as i thought ...that is something else i wondered though, given they were equal mm, f and distance how come the dof is so different? so is dof also inherently different per each lens?

 

[MarkBarbieri]

that is something else i wondered though, given they were equal mm, f and distance how come the dof is so different? so is dof also inherently different per each lens?

No, DOF should be the same for any two lenses at the same focal length and aperture.

I raised the issue of DOF as part of the focusing issue. If the lenses were focusing at different depths, the area's in focus would be different.

 

[jann1033]

i wondered about the dof when i looked at the photos...the canon was blurred in the background, the phoenix was sharper from the grass in the front to the trees in the background which made me wonder how the dof would be different.

 

[Groucho]

I'm not sure that I'm convinced that focusing really has anything to do with this shot... I don't see anything in the Canon picture that's sharper, at any distance, that in the Phoenix picture, but I see a lot that's sharper in the Phoenix one.

Generally, you just can't beat a prime. They don't have to make any compromises.

 

[mabas9395]

Like I've said before, I used to love my 28-135mm IS until I got my 85mm f/1.8. Now I only LIKE my 28-135 and I LOVE my 85mm.