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08-06-2009, 01:10 AM   #1
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k-7+FA50/1.4 vs. D90+AF50/1.4D

Hi All,

I am just trying to compare these two sets to determine which one should go. Here is some feelings. No scientific tests, just feelings.

1. Viewfinder: D90 seems larger in area, a little yellow with 50/1.4d. K-7 smaller, a little darker and a little red.

2. Sensitivity: At same light, K-7 need 1/3-1 stop more exposure than D-90. With same ISO/Tv/Av settings, K-7 is a little darker.

3. Low light AF: Although K-7 is a little faster than D90 in most cases, without assist light, K-7 is more difficult to lock in extremely low-light condition than D90.

In this comparison, D90 seems to win a little. I guess most of 2 and 3 could indicate the AF50/1.4d is superior to FA 50/1.4 in light amount point of view. Any thoughts?

About color comparison and K-7 front focus issues (in another post) I will post some test photos tomorrow.

Thanks,
Tony

08-06-2009, 04:17 AM   #2
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If you haven't already done so, you may also like to compare the sensor performance of the D90 and the K20D (as a proxy for the K7), as measured by DXO:

Welcome to dxomark.com (beta), a free resource dedicated to RAW-based camera image quality
08-06-2009, 10:07 AM   #3
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QuoteOriginally posted by fulcrumx29 Quote
Hi All,

2. Sensitivity: At same light, K-7 need 1/3-1 stop more exposure than D-90. With same ISO/Tv/Av settings, K-7 is a little darker.
1 stop is a lot; are you sure about this?
08-06-2009, 10:12 AM   #4
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Well, in some extreme low light case. In most cases it is 1/3 -1/2.

Thanks,
Tony

08-06-2009, 10:15 AM   #5
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Hi rawt,

Thanks for the link. D90 sensor seems superior to K20D's. Sad to know.

Tony
08-06-2009, 11:16 AM   #6
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Not that I put much weight into these numbers...

But if you do then I found the ISO Perfomance tab to be interesting (and somewhat revealing).

The K20 sensor is just below the 1:1 line. In other words at all settings the measured ISO was a little below the advertised value.

Whereas the D90 was consistently below the K20 (meaning the K20 is slightly more sensitive than the D90 sensor.


*EXCEPT* at ISO100!! the D90 measured the same ISO at 100 as at 200?!?!? If you believe these tests, then Nikon is misrepresenting its ISO range. it measured ISO145-4438 compared with the K20 at ISO 80-5357

so if you are comparing the cameras at BASE ISO all things equal, you are actually giving the D90 a one stop head start. I guess, depends on how you are comparing I suppose.
08-06-2009, 11:31 AM   #7
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Yes I noticed this. but I am using ISO 200 to compare. :-)
08-06-2009, 11:35 AM   #8
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Fulcrumx29

I actually did the same comparison that you did a few weeks ago when I was trying to decide what DSLR to go with.

I also noticed that the K-7 viewfinder seemed a little darker than the D90 - although I have a feeling that this has to do with the focusing screen. In bright daylight you can really notice the etching on it, which I've heard helps for manually focusing.

I did notice that they seemed to expose somewhat differently, but I wasn't paying that close attention to it to notice a trend there.

As for the focus speed in low light, I actually found that that the D90 hunted a lot more than the K-7 in general and in several cases couldn't get a lock - this is with the assist light on both cameras coming on. I've been really pleased with the K-7 in this respect - the only times I generally don't get a lock is when I happen to be too close to my subject (guess a macro's in my future...)

They both seemed like very nice cameras in the end. I didn't compare RAW images as I didn't have an editor that could process them both at the same time, but with jpegs I ran through the ISOs and NR settings and would probably give the edge there to the D90. In general though the IQ on both was more than good enough for me.

In the end though, I went with the K-7 for a few reasons - build quality, WR and size/weight of the kit. The D90 body is nice and light, but once you add some glass with the VR in it, the equation tips quite a bit toward Pentax. Size too, I can carry more in my bag if I want, and I don't really want to baby the gear too much, so the WR concept really appealed to me.

Hope this helps with your decision.

08-06-2009, 11:37 AM   #9
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QuoteOriginally posted by fulcrumx29 Quote
Hi All,

2. Sensitivity: At same light, K-7 need 1/3-1 stop more exposure than D-90. With same ISO/Tv/Av settings, K-7 is a little darker.
just to be sure, when you mean you need exposure compensation, is that to get the same camera settings on both, (aperture and shutter) or do you mean that there is a 20 point difference in greyscale value when shooting the same scene but the exposure values are different also?

I am just trying to determine if this is just the difference between one manufacturer and another in the set point they use for ISO. I seem to recall a discussion a while back about this issue and not all manufacturers set to the same point.

to be fair do a set of tests the first at each aperture for each camera, on a grey body (wall, road or what ever) and record / plot shutter speed and grey scale value of the image for each.\

this will tell us a lot about how each camera really meters
08-06-2009, 11:47 AM   #10
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Hi lowell,

At the same aperture and 0 EV, ISO 200, same light. The D90 in a case is 1/60 s and K-7 is 1/50 s but D90 is still as bright or a little brighter to me. I guess it is the lens. Nikon lens has a wider diameter. I am not sure if this will matter under the same aperture.

Thanks,
Tony
08-06-2009, 11:52 AM   #11
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QuoteOriginally posted by fulcrumx29 Quote
Hi lowell,

At the same aperture and 0 EV, ISO 200, same light. The D90 in a case is 1/60 s and K-7 is 1/50 s but D90 is still as bright or a little brighter to me. I guess it is the lens. Nikon lens has a wider diameter. I am not sure if this will matter under the same aperture.

Thanks,
Tony
actually it does not mean anything of the sort.

this is why you do the test at every aperture.

you could have anything from an aperture error in one lens or the other to a difference slightly in the ISO setting

look at the entire range before you make any judgement. as I said not all camera manufacturers interpret the ISO the same way
08-06-2009, 11:55 AM   #12
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Instead of pixel peeping, comparing miliseconds and whatnot, consider this:

weather sealing + built-in image stabilization. Nuff said.
08-06-2009, 12:02 PM   #13
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Hi Moo,

Thanks for your helpful remarks.

I had two 50/1.4s. I sold the old one and got another just yesterday. I found the package is different with a plastic bubble bag than the older paper set. I guess Hoya changed the way of Pentax packaging. I also wonder if the later made lens would be not as good as older ones, in regards of the red and darker lighting since I never noticed that on my DL and older 50/1.4. Have you noticed that?

In general I am pleased with K-7. The major reason why I don't like the D90 is the color accuracy. I tried every method to cutomize my image but just can't get it right. The red tends to pink, green tends to yellow and purple is too blue. Changing hue doesn't get it accurate. I guess the only accurate Nikon is D2x, whose color is really good, but I just cannot find a D2x mode 3 for D90. Pentax, in particular K-7 is better in this regard. I really love Pentax green color rendering.

Regarding the AF, I found D90's assist light is almost useless. It is good even without the annoying light. But K-7's light is useful and not so much annoying since it's green and not so bright. So that may be why with light, K-7 is better, and without, D90 is better in some cases. In general, K-7's motor feel stronger and quicker! I am really glad that Pentax fixed this problem.

In addition, I love K-7's outstanding AWB. It beats every camera that I have used. The feeling of the K-7 grip is far better than D90's plastic. The k-7 handling is OK, though I think D90 is more convinient since it has more buttons. The major complain about K-7 is the lack of quick SD formatting. D90's combination of button and dials are really smart operation. K-7's movie is way superior, though it has a bigger size.

In many ways I'd prefer K-7 but I have to solve the front focusing issue first. Maybe ordering a replacement from Amazon. Do you think it'll be different if I order from Pentax directly?

Many thanks,
Tony
08-06-2009, 12:51 PM   #14
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QuoteOriginally posted by fulcrumx29 Quote
Hi All,

I am just trying to compare these two sets to determine which one should go. Here is some feelings. No scientific tests, just feelings.

1. Viewfinder: D90 seems larger in area, a little yellow with 50/1.4d. K-7 smaller, a little darker and a little red.

2. Sensitivity: At same light, K-7 need 1/3-1 stop more exposure than D-90. With same ISO/Tv/Av settings, K-7 is a little darker.

3. Low light AF: Although K-7 is a little faster than D90 in most cases, without assist light, K-7 is more difficult to lock in extremely low-light condition than D90.

In this comparison, D90 seems to win a little. I guess most of 2 and 3 could indicate the AF50/1.4d is superior to FA 50/1.4 in light amount point of view. Any thoughts?

About color comparison and K-7 front focus issues (in another post) I will post some test photos tomorrow.

Thanks,
Tony
1) Not surprised. My experience with varies Nikon SLR/DSLRs indicate their VF are generally better than Pentax.

2) This could be due to the lack of precision with K mount apertures. I have found the apertures of my own primes could vary up to 1/2 stops when purchased brand new. This has much to do with the factory tolerance. Their parts manuals indicate the aperture calibration is based on an acceptable range instead of a single point. Also, due to their mechanical nature, the accuracy from f1.4 to f22 might not be as linear as we like.

3) I don't not know how much tricks Pentax have done on the K-7, but it is still based on the old 11 point AF sensor. I don't expect Pentax to address every issue w/o new design. If lowlight and predictive tracking are important to you, there are Canon and Nikon. Sad but we cannot milk what Pentax do not have.
08-06-2009, 01:16 PM   #15
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Hi wl,

I gree with you about 1 and 2, but 3 I think this time Pentax rolls!

I am happy with that,
Tony
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